**Synthesis and Properties of Polyurethanes Based on Synthetic Polyhydroxybutyrate for Medical Application**

## Joanna Brzeska

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/60933

## **Abstract**

Polyurethanes is a group of polymers whose unique properties make them useful in both the construction and the textile industry, and even in tissue engineering. One small, but very significant, urethane group connects specially selected macrochains to obtain a material with established properties.

The chapter is a literature review for research on the synthesis and properties of new degradable polyurethanes that contain soft segments synthesized with synthetic telechelic poly([R,S]-3-hydroxybutyrate) (R,S-PHB). Incorporation of oligomeric R,S-PHB (what was found degradable and biocompatible) into polyurethane structures gives them a chance of improving the properties important for medical applications. Aliphatic and aromatic polyurethanes with different soft segments were investigated due to their potential to be used in soft tissue regeneration.

**Keywords:** Polyurethanes, synthetic polyhydroxybutyrate, medical application

## **1. Introduction**

Polyurethane (PUR) is a large and very diverse group of polymers, including elastomeric and thermoplastic materials (liquid, millable), foams, and ionomers in the aqueous dispersions [1– 3]. The preparation of polyurethanes in such various forms has allowed their broad use in such industries as construction, engineering, automotive, textile, and medical. In medicine, their biocompatible, biostatic, and biodegradable properties are very desirable. The required

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

properties can be achieved using appropriate monomers for polyurethane synthesis and for preparing their composites.

## **1.1. Polyurethanes in medicine**

PURs' career in medicine has been going for almost 60 years since polyurethane foam for breast implants has been patented [4, 5]. According to studies of Jose Abel de la Pen˜a-Salcedo et al. [6] performed at the Institute for Plastic Surgery, polyurethane-covered implants are still the best option for breast reconstruction.

PURs are already used or investigated for utilization as membranes for wound dressing [7], as meniscal scaffold to treat partial meniscal loss [8], as drug nanocarriers for endovascular applications [9], as controlled release membrane system for delivery of ketoprofen [10], or as the biostable polyurethane/hydroxyapatite composites for bone replacement materials [11]. Whereas the shape memory PUR (based on PCL) used as wire in orthodontic appliance, could effectively align the teeth [12]. Waterborne polyurethane with chitosan as chain extender was also studied as antimicrobial agent for acrylic fabrics that could be used for the manufacture of blankets and carpets in hospitals [13].

One of the most important uses of PURs in medicine is the preparation of the implants for cardiovascular diseases, the use of which the specific properties of PUR (high mechanical strength, toughness and flexibility without the addition of modifiers, and good hemocompat‐ ibility resulting from occurring on the surface hydrophilic-hydrophobic balance) are very important.

## **1.2. Polyurethanes biostatic and biocidic**

The very important danger during implantation is connected with bacterial and fungi contamination. Aside from antibiotics treatment after surgery, the use of biostatic implant is essential for the success implantation.

The bacterial adherence and encrustation was reduced after the immobilization on PUR (Tecoflex®) surface by polyvinylpyrrolidone-iodine (PVP-I) complex [14]. Modified films were much more hydrophilic than original films.

Surfaces coated with quaternized PUR possessed the antibacterial and antiviral properties [15]. For wound dressing application, the asymmetric PUR membrane, with diamino containing antibiotic sulphanilamide used as a chain extender could be utilized [16]. These antibioticconjugated PUR are enzymatic susceptible what fit them antibacterial activity. The antibacte‐ rial properties can also be achieved by using nanoparticles for polyurethane or its composites obtaining. The nanosilver nanoparticles are very often used [17].

## **1.3. Biodegradable polyurethanes**

The first applications of polymers required their high resistance to environmental factors. They had to be stable (non-degradable) under the operating conditions throughout. This applies to the construction, packaging, textile, mechanical, medical, as well as other industries. However, the growing environmental burden of polymer waste has caused plastics to be gradually replaced by degradable materials. In medicine, dynamically developing tissue engineering suggests many interesting solutions with biodegradable polymeric materials.

PURs were originally considered to be very resistant to environmental impacts and were used in the construction of the first "artificial hearts". So why not produce something biocompatible as polyurethane and simultaneously degradable for tissue reconstruction? Since the first time this question was formulated, a lot of really interesting investigations were conducted.

The use of monomers susceptible to environmental factors allows the production of biode‐ gradable PURs potentially suitable to create scaffolds for the growth of living cells or as temporary implants. Hydrolysis-sensitive ester groups, mostly with oligomerols, are intro‐ duced into the PUR structure to build the soft segments.

Wang and co-workers [18] synthesized biodegradable polyurethanes with 11,11'-dithiodiun‐ decanol employed as a soft segment. They concluded that the molecular weight of PURs substantially decreased and the surface morphology was significantly eroded after 8 days of incubation in SBF with reduced glutathione. Gisele Rodrigues da Silva et al. [19] observed that the biodegradable PURs based on PCL were able to release dexamethasone acetate for 371 days at almost constant rates.

## **1.4. Polyurethanes that are more biocompatible**

properties can be achieved using appropriate monomers for polyurethane synthesis and for

PURs' career in medicine has been going for almost 60 years since polyurethane foam for breast implants has been patented [4, 5]. According to studies of Jose Abel de la Pen˜a-Salcedo et al. [6] performed at the Institute for Plastic Surgery, polyurethane-covered implants are still the

PURs are already used or investigated for utilization as membranes for wound dressing [7], as meniscal scaffold to treat partial meniscal loss [8], as drug nanocarriers for endovascular applications [9], as controlled release membrane system for delivery of ketoprofen [10], or as the biostable polyurethane/hydroxyapatite composites for bone replacement materials [11]. Whereas the shape memory PUR (based on PCL) used as wire in orthodontic appliance, could effectively align the teeth [12]. Waterborne polyurethane with chitosan as chain extender was also studied as antimicrobial agent for acrylic fabrics that could be used for the manufacture

One of the most important uses of PURs in medicine is the preparation of the implants for cardiovascular diseases, the use of which the specific properties of PUR (high mechanical strength, toughness and flexibility without the addition of modifiers, and good hemocompat‐ ibility resulting from occurring on the surface hydrophilic-hydrophobic balance) are very

The very important danger during implantation is connected with bacterial and fungi contamination. Aside from antibiotics treatment after surgery, the use of biostatic implant is

The bacterial adherence and encrustation was reduced after the immobilization on PUR (Tecoflex®) surface by polyvinylpyrrolidone-iodine (PVP-I) complex [14]. Modified films were

Surfaces coated with quaternized PUR possessed the antibacterial and antiviral properties [15]. For wound dressing application, the asymmetric PUR membrane, with diamino containing antibiotic sulphanilamide used as a chain extender could be utilized [16]. These antibioticconjugated PUR are enzymatic susceptible what fit them antibacterial activity. The antibacte‐ rial properties can also be achieved by using nanoparticles for polyurethane or its composites

The first applications of polymers required their high resistance to environmental factors. They had to be stable (non-degradable) under the operating conditions throughout. This applies to the construction, packaging, textile, mechanical, medical, as well as other industries. However,

preparing their composites.

**1.1. Polyurethanes in medicine**

2 Thermoplastic Elastomers - Synthesis and Applications

best option for breast reconstruction.

of blankets and carpets in hospitals [13].

**1.2. Polyurethanes biostatic and biocidic**

essential for the success implantation.

**1.3. Biodegradable polyurethanes**

much more hydrophilic than original films.

obtaining. The nanosilver nanoparticles are very often used [17].

important.

Using of natural components (or their synthetic substitutes) for PURs synthesis is one of method for making them more biocompatible. Saralegi et al. used castor oil for soft segment building [20]. They obtained the shape memory thermoplastic PUR due to the addition of cellulose nanocrystals. L-arginine, glycine, and L-aspartic acid were used as chain extenders in poly(urea)urethanes synthesis by the Chan-Chan group [21]. The authors concluded that PURs containing L-arginine would be a potential candidate for cardiovascular applications and angiogenesis. Studies of Lin Jia and co-workers [22] showed the lack of cytotoxicity of PUR/collagen and PUR/gelatin nanofibrous scaffolds. The authors indicated on sufficient mechanical properties, supported SMC proliferation, and assisted in oriented morphological alignment of cells of PURs with L-arginine that make them the appropriate candidate for vascular tissue engineering.

Very important for obtaining biocompatible material is the use for their synthesis substrates that are non-toxic and degraded into non-toxic compounds. In medical applications, 4,4' methylene dicyclohexyl diisocyanate (H12MDI) successfully replaced 4,4'-diphenylmethane diisocyanate (MDI), especially in the synthesis of biodegradable materials, thereby reducing the risk of creation of carcinogenic aromatic diamine as degradation product of PUR based on MDI.

Using natural components for polyurethanes building very often gives them a chance to be biocompatible and degradable simultaneously. The important groups of substrates useful for polyurethanes synthesis are polyhydroxyacids (PHA). Among them, polyhydroxybutyrate (PHB) is the most often used.

## **1.5. Biosynthesized polyhydroxybutyrate**

As it was mentioned before, the most popular polyhydroxyacid is PHB. Since the 1920s when Lemoigne found the bacterial granules of supplementary material (later called polyhydroxy‐ butyrate) in *Bacillus megaterium*, intensive researches on the biological and chemical obtaining of PHB, its properties, and application were conducted. The natural origin, biodegradability, and biocompatibility of polyhydroxybutyrate made it such interesting material for medical applications whereas its low water vapor permeability, which is close to that low-density polyethylene, promote it to food packaging applications [23].

PHB degrades into 3-hydroxybutyric acid, a common metabolite in human blood. 3 hydroxybutyric acid is produced in ketone bodies of mammals during the prolonged starvation [24]. 3-hydroxybutyric acid belongs to short-chain fatty acids and reveals antibacterial activity [25].

A lot of investigations suggest that PHB is non-genotoxic [26]. All this features promote PHB for medical applications. Lee and co-workers prepared a carrier system with target‐ ing capability for imaging and drug delivery to cancer cells using catalytic characteristics of PHA synthase [27]. They found an attractive way of preparing functionalized nanopar‐ ticles by effective coupling between the hydrophobic surface of PHB nanoparticle and PHB chain grown from the fusion enzyme. Medvecký and co-workers [28] found that the addition of hydrophobic PHB microparticles into the calcium phosphate cement significantly improves the initial cement properties (the higher tensile and compressive strengths) and makes it a very promising material for bone substituting. Another way of PHB utilization in tissue reconstruction is by using it as the PHB–chitosan biopolymer scaffolds [29], PHBcalcium phosphate/chitosan barrier membrane [30], hydroxyapatite/PHB composites [31], or biodegradable stents [32]. The investigations of Shishatskaya at el. [33, 34] indicate that PHB is a good candidate for fabricating prolonged-action drugs as microparticles intend‐ ed for intramuscular injection. Whereas Althuri and co-workers [35] concluded that folate functionalized PHB nanoparticles can be used as a polymer matrix to carry toxic drug compounds to targeted sites for treatment of life-threatening diseases such as cancer.

Nonetheless, the inherent brittleness and stiffness (connected to its semicrystalline nature) and inferior thermal stability, in addition to relative high cost, have blocked the popular use of PHB.

It is known that even the short exposure of PHB to temperatures near 180°C degrades it to olefinic and carboxylic acid compounds (e.g., crotonic acid) and various oligomers. Also, during storage, the degree of crystallization of polymer increases and causes the forma‐ tion of irregular pores on its material surface and causes even higher stiffness. These disadvantages can be reduced by mixing of PHB with plasticizers, such as low molecular weight PHB [36], carboxyl-terminated butadiene acrylonitrile rubber, or biocompatible polyvinylpyrrolidone polymeric additives [37].

## **1.6. Chemically synthesized poly([R,S]-3-hydroxybutyrate)**

The chemically synthesized substitute of natural PHB is synthetic poly([R,S]-3-hydroxybuty‐ rate) (R,S-PHB). Synthetic R,S-PHB can be obtained by anionic ring-opening polymerization of (R,S)-ß-butyrolactone. The supramolecular acid sodium salt complex of 3-hydroxybutyric acid ether 18-crown-6 can then be used as the initiator. The polymerization process is carried out in THF at room temperature. The resulting polymer could be reacted with 2-bromo- or 2 iodoethanol, finally causing PHB to be terminated with hydroxy groups on both sides [38–41].

**1.5. Biosynthesized polyhydroxybutyrate**

4 Thermoplastic Elastomers - Synthesis and Applications

antibacterial activity [25].

use of PHB.

polyvinylpyrrolidone polymeric additives [37].

**1.6. Chemically synthesized poly([R,S]-3-hydroxybutyrate)**

polyethylene, promote it to food packaging applications [23].

As it was mentioned before, the most popular polyhydroxyacid is PHB. Since the 1920s when Lemoigne found the bacterial granules of supplementary material (later called polyhydroxy‐ butyrate) in *Bacillus megaterium*, intensive researches on the biological and chemical obtaining of PHB, its properties, and application were conducted. The natural origin, biodegradability, and biocompatibility of polyhydroxybutyrate made it such interesting material for medical applications whereas its low water vapor permeability, which is close to that low-density

PHB degrades into 3-hydroxybutyric acid, a common metabolite in human blood. 3 hydroxybutyric acid is produced in ketone bodies of mammals during the prolonged starvation [24]. 3-hydroxybutyric acid belongs to short-chain fatty acids and reveals

A lot of investigations suggest that PHB is non-genotoxic [26]. All this features promote PHB for medical applications. Lee and co-workers prepared a carrier system with target‐ ing capability for imaging and drug delivery to cancer cells using catalytic characteristics of PHA synthase [27]. They found an attractive way of preparing functionalized nanopar‐ ticles by effective coupling between the hydrophobic surface of PHB nanoparticle and PHB chain grown from the fusion enzyme. Medvecký and co-workers [28] found that the addition of hydrophobic PHB microparticles into the calcium phosphate cement significantly improves the initial cement properties (the higher tensile and compressive strengths) and makes it a very promising material for bone substituting. Another way of PHB utilization in tissue reconstruction is by using it as the PHB–chitosan biopolymer scaffolds [29], PHBcalcium phosphate/chitosan barrier membrane [30], hydroxyapatite/PHB composites [31], or biodegradable stents [32]. The investigations of Shishatskaya at el. [33, 34] indicate that PHB is a good candidate for fabricating prolonged-action drugs as microparticles intend‐ ed for intramuscular injection. Whereas Althuri and co-workers [35] concluded that folate functionalized PHB nanoparticles can be used as a polymer matrix to carry toxic drug compounds to targeted sites for treatment of life-threatening diseases such as cancer.

Nonetheless, the inherent brittleness and stiffness (connected to its semicrystalline nature) and inferior thermal stability, in addition to relative high cost, have blocked the popular

It is known that even the short exposure of PHB to temperatures near 180°C degrades it to olefinic and carboxylic acid compounds (e.g., crotonic acid) and various oligomers. Also, during storage, the degree of crystallization of polymer increases and causes the forma‐ tion of irregular pores on its material surface and causes even higher stiffness. These disadvantages can be reduced by mixing of PHB with plasticizers, such as low molecular weight PHB [36], carboxyl-terminated butadiene acrylonitrile rubber, or biocompatible

The chemically synthesized substitute of natural PHB is synthetic poly([R,S]-3-hydroxybuty‐ rate) (R,S-PHB). Synthetic R,S-PHB can be obtained by anionic ring-opening polymerization

**Figure 1.** Scheme of how telechelic R,S-PHB (OH-terminated) and R,S-PHB (OH- and COOH-terminated) are obtained.

The literature indicated that materials obtained with synthetic R,S-PHB was biocompatible and biodegradable. The degradation products of the temporary patch made from PHB/R,S-PHB blends were metabolized and did not evoke inflammatory reactions [42]. Freier et al. [43] found that after 26 weeks of implantation of the patches (made with PHB/R,S-PHB blends) in the abdomen of rats, the loss of intestines of animals was almost completely restored and the introduced material had been substantially degraded.

Piddubnyak et al. [40] conducted a series of studies confirming the biocompatibility and non-toxicity of synthetic [R,S]-3-hydroxybutyrate oligomerols. The possibility of their formation into spherical particles of a diameter <1 micron, suggested that they could be used in obtaining nonsteroidal anti-inflammatory drugs. In the form of an aqueous dispersion, they could be introduced into the body through intravenous, intramuscular, or subcutaneous administration [44].

## **1.7. Marriage of PUR and PHB advantages in one product**

Using for PUR synthesis, almost completely amorphous R,S-PHB that is close to its original state in the cell, ought to be utilized to obtain biocompatible and biodegradable material useful for medical application.

The work is a review of the research on the synthesis and properties of PURs containing synthetic poly([R,S]-3-hydroxybutyrate) and polycaprolactonediol or polyoxytetramethyle‐ nediol in soft segments in the structure in terms of applications as medical devices. The properties of polyurethanes that could determine their usefulness for medical application (structure, morphology of surface, thermal and mechanical properties, water and oil sorption, density, degradability, spinnability, compatibility, and biostatic properties) were estimated.


Works with PURs based on natural and synthetic PHB are collected in Table 1.

**Table 1.** Polyurethanes based on PHB.

## **2. Experimental**

## **2.1. Materials**

Oligoesters, such as polycaprolactonediol (PCL) and polyhydroxybutyratediol (PHB), are used in the synthesis of polyesterurethanes. The oxidative-sensitive ether groups can be introduced into polyurethanes with polyoxytetramethylenediol (PTMG). 4,4'-diphenylmethane diisocya‐ nate (MDI) and 4,4'-methylene dicyclohexyl diisocyanate (H12MDI) are isocyanates that are often used for building of hard segments of polyurethanes.

Aromatic and aliphatic polyurethanes with synthetic poly([R,S]-3-hydroxybutyrate) incorpo‐ rated into the soft segments structure were obtained and investigated.

## *2.1.1. Materials for polyurethanes synthesis*


## *2.1.2. Polyurethane synthesis and sample preparation*

nediol in soft segments in the structure in terms of applications as medical devices. The properties of polyurethanes that could determine their usefulness for medical application (structure, morphology of surface, thermal and mechanical properties, water and oil sorption, density, degradability, spinnability, compatibility, and biostatic properties) were estimated.

**Kind of PHB origin Characteristic Ref.** bacterial Higher crystallinity than PURs without PHB. [45] bacterial (as copolymer P3/4HB) High molecular weight and narrow molecular weight distribution. [46] bacterial (as copolymer P3/4HB) Narrow distribution and suitable crystallinity to prepare films and pads. Non-toxic for cell growth and proliferation.

bacterial Degradability with creation of 3-hydroxybutyric acid and crotonic acid as

synthetic The way of PURs based on R,S-PHB obtaining. [50] synthetic Presence of R,S-PHB influenced on the structure of PURs. [51] synthetic Degradability of PURs increased after using of R,S-PHB for their building. [52] synthetic Electrospinning of PURs based on R,S-PHB. [53] synthetic Degradability of PURs increased after using of R,S-PHB for their building. [54]

Oligoesters, such as polycaprolactonediol (PCL) and polyhydroxybutyratediol (PHB), are used in the synthesis of polyesterurethanes. The oxidative-sensitive ether groups can be introduced into polyurethanes with polyoxytetramethylenediol (PTMG). 4,4'-diphenylmethane diisocya‐ nate (MDI) and 4,4'-methylene dicyclohexyl diisocyanate (H12MDI) are isocyanates that are

Aromatic and aliphatic polyurethanes with synthetic poly([R,S]-3-hydroxybutyrate) incorpo‐

**•** Before the synthesis of polyurethanes, R,S-PHB (Mn~2000) (CMPW, PAN Zabrze), PCL (Mn~2000) (Aldrich), and PTMG (Mn~2000) (Aldrich) were dried by heating at 60°C–90°C

**•** 4,4'-diphenylmethane diisocyanate MDI (Aldrich) was filtered and melted at temperature

synthetic Hydrolytic degradation of PURs based on PCL/HB increased with increasing of PHB fraction.

degradation products.

often used for building of hard segments of polyurethanes.

*2.1.1. Materials for polyurethanes synthesis*

for 3 h under reduced pressure;

rated into the soft segments structure were obtained and investigated.

**Table 1.** Polyurethanes based on PHB.

6 Thermoplastic Elastomers - Synthesis and Applications

**2. Experimental**

**2.1. Materials**

40°C;

[47]

[48]

[49]

Works with PURs based on natural and synthetic PHB are collected in Table 1.

The synthesis of polyurethanes was carried out in a two-step reaction at the vacuum reactor, as previously described [56].

First, the prepolymer was prepared from oligomerols and H12MDI or MDI, at 60°C–90°C in a presence of a catalyst at reduced pressure according to the appropriate required molar ratio of NCO:OH groups for 2–3 h. Oligomerols used in synthesis: a mixture of PCL and R,S-PHB or a mixture of PTMG and R,S-PHB. For comparison, PURs based only on PCL or PTMG without R,S-PHB were also obtained. The synthesis of prepolymer was carried on mass but next the prepolymer was dissolved in DMF to solid mass concentration of 40%. The chain extender (1,4-BD) was added to obtain equimolar ratio NCO:OH groups. The propagation reaction of prepolymer was carried on for 2–3 h at 60°C.


**Table 2.** Composition of the obtained polyurethanes.

After the extension of prepolymer chains, the solution of polyurethane was poured on Teflon plates and heated for solvent evaporating (2 h/80°C). Next, the foils were heated in a vacuum dryer for reaction completing (5 h/105°C). Before the estimation of polyurethanes properties, the foils were conditioned at room temperature at least 2 weeks.

The obtained and investigated PURs differed in soft and hard segment structures and in their ratio (Table 2).

## **2.2. Methods of investigations, obtained results, and discussion**

## *2.2.1. The structure of obtained polyurethanes*

The structures of obtained aromatic and aliphatic PURs were investigated using FT-IR and 1 HNMR methods (results presented in [51]).

The value of vibration absorption of the carbonyl group in the ester moiety at 1,740 cm-1 is indicative of the presence of the amorphous phase of polyhydroxybutyrate (the presence of the crystal phase of stretching vibration of C=O would be observed at 1,725 cm-1) [56, 57]. These differences in the frequencies corresponding to the vibrations of the carbonyl bond were explained by Wu and co-workers [58] by the decrease in oxygen dipole moment under the influence of hydrogen from a neighboring chain. The interaction is stronger when the oxygen is closer to the hydrogen atom. Amorphousness of R,S-PHB used in the synthesis of polyur‐ ethane, was also confirmed by the presence of bands of CH3 at 2,985 cm-1 and C-O-C stretching vibration band at 1,186 cm-1 [57, 59]. It is known that asymmetric stretching vibration of CH3 at 3,009 cm-1, 2,995 cm-1, 2,974 cm-1, and 2,967 cm-1 in the natural polyhydroxybutyrate indicate its crystallinity [57].

**Figure 2.** FT-IR spectra of substrates and PUR-3A-1 (a) and substrates and PUR-3A-3 (b).

FT-IR spectra supported the formation of urethane groups during polyaddition reaction of OH groups of oligomerols (R,S-PHB, PCL, and PTMG) and NCO groups of diisocyanates (MDI and H12MDI).

In the spectra of PUR-2 and PUR-3 series with PTMG in soft segments (PUR-2A-2, PUR-2B-2, PUR-3A-2 and PUR-3B-2), a single band (without shoulder) at around 3,330 cm-1 corresponded to the NH stretching vibration of urethane groups. The absence of any bands above 3,500 cm-1 indicated that all group -NH were involved in the formation of hydrogen bonds.

Simultaneously, in an area corresponding to the stretching vibration of C=O groups of the urethane two bands (at 1,720 cm-1/1,705 cm-1 for PUR-3 and at around 1,732 cm-1/1,703 cm-1 for PUR-2) were observed. The intensities of these bands were comparable for PUR-3A-2. The literature indicated that the first band corresponded to vibration of free groups C=O and the other for associated groups [60]. The presence of free groups C=O suggested that not all -NH were involved in the formation of hydrogen bonds within the urethane groups, but some of them could be associated with the oxygen moiety of ether. The intensity of the absorption bands of the C=O hydrogen bonded clearly decreased after the introduction of R,S-PHB into the soft segments. On spectra PUR-3A-1 at 1,740 cm-1 appeared the band of stretching vibration characteristic for non-hydrogen bonded C=O of ester groups.

In the spectra of all polyurethanes with PCL in their structure, there were clear bands of stretching vibration characteristic for associated -NH. For polymers PUR-2 they were at 3,334 cm-1 and at about 3,360 cm-1 for PUR-3. At frequencies a bit lower, the presence of broad bands with low intensity was also observed. It indicates the existence of two types of hydrogen bonds, between the -NH groups and the carbonyl group of urethane and between -NH and ester group. On the other hand, the intensity of the bands of stretching, hydrogen-bonded C=O of urethane (amide I band) and ester groups on PUR-2A-3 and PUR-2A-4 spectra (at 1,702 cm-1 and 1,705 cm-1) was small.

Thus, the FT-IR spectra of the polyurethanes indicated that urethane groups (partly hydrogen bonded) were formed and the end groups of substrates were completely converted.

On 1 HNMR spectra of aliphatic PURs, peaks due to the NH group were observed in the region of 6.6–7.1 ppm [51], whereas on the spectra of aromatic PUR they were located at 9.2–9.5 ppm. The NH groups coming from urethane groups were forming hydrogen bonds with carbonyl groups of ester and urethane groups and the hydrogen bonds with ether groups. It was also concluded that the greater NCO:OH ratio, the more urethane-urethane hydrogen bonds were formed [51]. An addition, R,S-PHB caused the slight increase in number of urethane-urethane hydrogen bonds. The presence of an allophanate structures was observed at 8.5 ppm (for aromatic PURs) and as a very small peak at 9.65 ppm (for aliphatic polyurethanes based on PTMG).

## *2.2.2. Thermal properties*

The obtained and investigated PURs differed in soft and hard segment structures and in their

The structures of obtained aromatic and aliphatic PURs were investigated using FT-IR and

The value of vibration absorption of the carbonyl group in the ester moiety at 1,740 cm-1 is indicative of the presence of the amorphous phase of polyhydroxybutyrate (the presence of the crystal phase of stretching vibration of C=O would be observed at 1,725 cm-1) [56, 57]. These differences in the frequencies corresponding to the vibrations of the carbonyl bond were explained by Wu and co-workers [58] by the decrease in oxygen dipole moment under the influence of hydrogen from a neighboring chain. The interaction is stronger when the oxygen is closer to the hydrogen atom. Amorphousness of R,S-PHB used in the synthesis of polyur‐ ethane, was also confirmed by the presence of bands of CH3 at 2,985 cm-1 and C-O-C stretching vibration band at 1,186 cm-1 [57, 59]. It is known that asymmetric stretching vibration of CH3 at 3,009 cm-1, 2,995 cm-1, 2,974 cm-1, and 2,967 cm-1 in the natural polyhydroxybutyrate indicate

(a) (b)

FT-IR spectra supported the formation of urethane groups during polyaddition reaction of OH groups of oligomerols (R,S-PHB, PCL, and PTMG) and NCO groups of diisocyanates (MDI

**Figure 2.** FT-IR spectra of substrates and PUR-3A-1 (a) and substrates and PUR-3A-3 (b).

**2.2. Methods of investigations, obtained results, and discussion**

*2.2.1. The structure of obtained polyurethanes*

8 Thermoplastic Elastomers - Synthesis and Applications

HNMR methods (results presented in [51]).

ratio (Table 2).

its crystallinity [57].

and H12MDI).

1

The presence of the synthetic R,S-PHB (with a lateral methyl group) in soft segments caused a disturbance in the phase separation and increase the glass transition temperature (estimated by DSC at a heating rate of 20°/min, at a temperature ranging from - 80°C to + 200°C) of the aromatic and aliphatic PURs in comparison to PURs without R,S-PHB [61,62].


**Table 3.** Thermal properties of oligomerols and polyurethanes (results presented in [61, 62]).

Incorporation of oligomerols into PUR structures generally increased their glass temperatures. Moreover, using R,S-PHB for soft segment building increased the Tg of soft segments.

Obtained PURs were amorphous with the low value of crystalline phase. The introduction of R,S-PHB into PUR structures generally reduced crystallinity of soft segments (lower melting enthalpy was observed) [53]. In particular, it caused the reduced susceptibility of PCL to crystallization, which was the result of partial miscibility of both oligoestroles [62].

Temperatures in the range 90°C–179°C indicated the presence of long-range order of hard segments. A few melting endotherms on DSC thermograms (in the mentioned range) of aliphatic PURs (series PUR-3) were probably the result of using nonlinear diisocyanate for hard segment building. H12MDI was a mixture of stereoisomers that may be formed into crystallites with different construction and size, and polymorphism.

The low degree of crystallinity suggested that investigated PURs could be degradable under the conditions of a living body.

## *2.2.3. Microscopic observation*

The surfaces of the samples and surfaces revealed after breaking of obtained PUR samples in liquid nitrogen (cryogenically broken samples), they were tested by Transmission Electron Microscopy (TEM) using a two-step replica.

Studies of electron microscopy of PUR samples showed that they were characterized by varying degrees of homogeneity of the physical (morphological), depending on the chemical composition of the polymers. For samples with reported crystallization of soft segments, crystalline elements were usually in the form of spherulites.

The surface of aromatic polyurethane PUR-2A series samples was smooth or only slightly rough. The cryogenically fractured surface of these samples were homogeneous in the micrometer scale, which indicated that the cracking (during the preparation of the samples) occurred between the crystalline areas, and thus in the weaker points of the polymers. The observed morphology was characteristic of non-crosslinked polymers. It was called un-radial or "mount-depression" morphology [63].

The aliphatic PUR surfaces and their cryogenically fractured surfaces were a bit rougher than the aromatic ones and that could influence their degradability. The surface morphology was comparable for all investigated samples.

There were no significant differences in the morphology of the samples of PUR based on PTMG or PCL. It was found, however, that the introduction of poly([R,S]-3-hydroxybutyrate) into the soft segment structures resulted in a slight decrease in the roughness of the surface of test samples and that could favorably influence the adhesion of blood elements in the study of the effects on blood parameters of polymers [64].

## *2.2.4. Mechanical properties*

**sample**

**Tg [°C]**

10 Thermoplastic Elastomers - Synthesis and Applications

**Tm1 [°C]**

**Table 3.** Thermal properties of oligomerols and polyurethanes (results presented in [61, 62]).

crystallites with different construction and size, and polymorphism.

the conditions of a living body.

Microscopy (TEM) using a two-step replica.

crystalline elements were usually in the form of spherulites.

*2.2.3. Microscopic observation*

**ΔH<sup>1</sup> [J/g]**

**PTMG** -70.8 47.8 129.6 - - **PCL** -60.8 68.3 84.5 - - **R,S-PHB** -12.3 56.3 4.3 - - **PUR-2A-1** -67.6 - - 174.1 1.3 **PUR-2A-2** -73.3 35.0 2.0 177.0 12.6 **PUR-2A-3** -28.5 44.0 1.4 175.2 7.3 **PUR-2A-4** -38.5 51.3 2.8 179.1 5.7 **PUR-3A-1** -55.3; -10.5 37.8 0.7 107.4; 135.9; 157.5 2.5; 4.0; 2.2 **PUR-3A-2** -55.3 39.8 0.8 164.5 17.0 **PUR-3A-3** -32.4 50.7 3.6 90.2; 138.1 4.7; 9.1 **PUR-3A-4** -49.1 50.2 19.5 107.7; 131.6; 143.0 5.0; 5.1; 2.9

Incorporation of oligomerols into PUR structures generally increased their glass temperatures. Moreover, using R,S-PHB for soft segment building increased the Tg of soft segments.

Obtained PURs were amorphous with the low value of crystalline phase. The introduction of R,S-PHB into PUR structures generally reduced crystallinity of soft segments (lower melting enthalpy was observed) [53]. In particular, it caused the reduced susceptibility of PCL to

Temperatures in the range 90°C–179°C indicated the presence of long-range order of hard segments. A few melting endotherms on DSC thermograms (in the mentioned range) of aliphatic PURs (series PUR-3) were probably the result of using nonlinear diisocyanate for hard segment building. H12MDI was a mixture of stereoisomers that may be formed into

The low degree of crystallinity suggested that investigated PURs could be degradable under

The surfaces of the samples and surfaces revealed after breaking of obtained PUR samples in liquid nitrogen (cryogenically broken samples), they were tested by Transmission Electron

Studies of electron microscopy of PUR samples showed that they were characterized by varying degrees of homogeneity of the physical (morphological), depending on the chemical composition of the polymers. For samples with reported crystallization of soft segments,

crystallization, which was the result of partial miscibility of both oligoestroles [62].

**Tm2 [°C]**

**ΔH<sup>2</sup> [J/g]**

> The mechanical properties determined for the obtained PUR materials included hardness (in degrees Shore A), tensile strength (Rr), and elongation at break (εr).


**Table 4.** The hardness and tensile strength (±standard deviation) before and after the sterilization of PURs (results partially presented in [61,62]).

It was concluded that incorporation of R,S-PHB into aromatic and aliphatic PUR structures slightly reduced their tensile strength and elongation. The hardness of polyurethanes was in the range of commercial polyurethane elastomers used in medicine [61, 62].

The tensile strength of PURs obtained with the participation of the aliphatic diisocyanate (H12MDI) was generally lower than PURs containing asymmetric and aromatic MDI. Investi‐ gations of model PURs (constructed only with H12MDI and PTMG, without chain extenders), indicated that in these polymers disordered hydrogen bonding were formed, making the phase separation of soft and hard segments difficult what reduced the mechanical strength of the materials [60].

The influence of sample sterilization on their mechanical properties was estimated. Gas plasma technology (dihydrogen peroxide) was used for sterilization. In some cases, tensile strength (Rrster.) and elongation at the break (εrster.) of samples increased after the steriliza‐ tion process. During the plasma sterilization, the free radicals were generated that could lead to slight cross-linking chains, thereby increasing the elasticity and tensile strength of the obtained PURs [61, 62].

## *2.2.5. Density*

Easy penetration of water and degrading factors into the material is an important factor in the degradation of polymers. The density of the material is one of the parameters that determine the sorption of water.


**Table 5.** Density of polyurethanes (results partially presented in [54, 61, 62, 65]).

## *2.2.6. The oil and water sorption*

The implanted material, immersed into a living body is affected by surrounding solutions. Physiological body fluids are constituted of water and floating inorganic and organic com‐ pounds, such as lipids. The tendency of water and lipids sorption by polymer is important for its stability in natural conditions. Water plays a key role in the process of hydrolysis whereas lipids accelerate calcification and environmental stress cracking of PUR surfaces. Moreover, the tendency for oil sorption could predispose polymer to albumin sorption. Albumin is peptide absorbable on implant surface what makes the natural junction with natural environ‐ ment.

The sunflower oil and water sorption by PUR samples were performed at the physiologic temperature of the human body (37°C).

It was stated that the oil sorption by PUR samples based on PTMG and R,S-PHB was much higher than for PURs with PCL and R,S-PHB in soft segments [65, 66].

As it was expected, aliphatic PURs (based on asymmetric diisocyanate) absorbed more oil than aromatic ones. The oil sorption by aliphatic and aromatic PURs were significantly reduced after the introduction of R,S-PHB into soft segments based on PTMG [61, 62]. It could suggest an increase the hydrophility of PURs after R,S-PHB incorporation into their structure. More‐ over, it indicated that PURs based on PTMG could be more biocompatible (according to their affinity to lipids) than PURs with PCL.


**Table 6.** The weight changes of PUR samples after incubation in sunflower oil (results partially presented in [61, 62, 65]).

Estimated wetting angle (57°C–71°C) suggested that PURs were hydrophilic [64]. But they absorbed a very low amount of water and only a bit higher in the case of using of PTMG for soft segments building. As mentioned before, the glass temperature of soft segments of polyetherurethanes and polyether-esterurethanes (Table 3) was lower than Tg of polyester‐ urethanes (PURs with PCL and PCL+R,S-PHB). Lower glass temperature was connected to them being less stiff than polyesterurethanes [67]. In case when the chains were stiff, their mobility was reduced so water could not penetrate easy between them. Higher water absorp‐ tion by PURs based on PTMG could suggest their higher susceptibility to degradation in aqueous medium. In a PUR network, the particles (such as free radicals and enzymes) that could facilitate its degradation may penetrate with the water.

The presence of R,S-PHB in soft segments increased the water sorption of aromatic PURs [61].

## *2.2.7. Bacteriostatic properties*

indicated that in these polymers disordered hydrogen bonding were formed, making the phase separation of soft and hard segments difficult what reduced the mechanical strength of the

The influence of sample sterilization on their mechanical properties was estimated. Gas plasma technology (dihydrogen peroxide) was used for sterilization. In some cases, tensile strength (Rrster.) and elongation at the break (εrster.) of samples increased after the steriliza‐ tion process. During the plasma sterilization, the free radicals were generated that could lead to slight cross-linking chains, thereby increasing the elasticity and tensile strength of

Easy penetration of water and degrading factors into the material is an important factor in the degradation of polymers. The density of the material is one of the parameters that determine

**PUR-2A-1** 1.098±0.024 **PUR-3A-1** 1.081±0.002 **PUR-2A-2** 1.089±0.004 **PUR-3A-2** 1.051±0.004 **PUR-2A-3** 1.189±0.007 **PUR-3A-3** 1.152±0.008 **PUR-2A-4** 1.177±0.008 **PUR-3A-4** 1.135±0.003

The implanted material, immersed into a living body is affected by surrounding solutions. Physiological body fluids are constituted of water and floating inorganic and organic com‐ pounds, such as lipids. The tendency of water and lipids sorption by polymer is important for its stability in natural conditions. Water plays a key role in the process of hydrolysis whereas lipids accelerate calcification and environmental stress cracking of PUR surfaces. Moreover, the tendency for oil sorption could predispose polymer to albumin sorption. Albumin is peptide absorbable on implant surface what makes the natural junction with natural environ‐

The sunflower oil and water sorption by PUR samples were performed at the physiologic

It was stated that the oil sorption by PUR samples based on PTMG and R,S-PHB was much

As it was expected, aliphatic PURs (based on asymmetric diisocyanate) absorbed more oil than aromatic ones. The oil sorption by aliphatic and aromatic PURs were significantly reduced after the introduction of R,S-PHB into soft segments based on PTMG [61, 62]. It could suggest

higher than for PURs with PCL and R,S-PHB in soft segments [65, 66].

**PUR Density ±SD**

**[g/cm3 ]**

materials [60].

*2.2.5. Density*

the sorption of water.

*2.2.6. The oil and water sorption*

temperature of the human body (37°C).

ment.

**PUR Density ±SD**

**[g/cm3 ]**

**Table 5.** Density of polyurethanes (results partially presented in [54, 61, 62, 65]).

the obtained PURs [61, 62].

12 Thermoplastic Elastomers - Synthesis and Applications

The influence of polyurethane PUR-3A-3 on microorganisms (*Staphylococcus aureus*, *Escherichia coli*, and *Candida albicans*) was investigated using disk methods [68, 69]. The *Staphylococcus aureus* growth around PUR samples was the most inhibited. The bacterial growth was inhibited for 6 mm around a circle sample (diameter of the sample was 8 mm). Knowing that 3 hydroxybutyrate belonging to fatty acids revealed antibacterial activity, it was concluded that R,S-PHB was responsible for the decreasing microorganism growth [68]. But the determined number of survival *Staphylococcus aureus* bacteria directly contacted with PUR sample PUR-3A-3 in a tube method showed only slight decrease of bacteria quantity in comparison to control probe [69]. It suggested its bacteriostatic but no bactericidal properties.

## *2.2.8. Hemocompatibility*

Hemocompatibility of obtained PURs was estimated by observations of changes in morphol‐ ogy and coagulation parameters of whole blood after 4 h of direct contact with polymer samples using flow cytometry and photooptical methods [64, 65].


**Table 7.** Blood parameters after direct contact with PUR samples and those without contact.

The values of hematologic parameters before and after the incubation of PUR samples in blood were in reference ranges. Differences in comparison to the control probe were not observed that suggests the lack of hemolysis activated by polyurethane presence. Insignificant changes in platelet and fibrinogen concentration and in APPT during direct contact of blood with polymer samples suggested that polyurethanes based on synthetic poly([R,S]-3-hydroxybu‐ tyrate) could be atrombogenic [65].

## *2.2.9. Degradability*

The influence of the surrounding environment on implanted material can be simulated using hydrolytic and oxidative solutions. Also, simulated body fluids (SBF) and Ringer solutions included ions that could be found in natural fluids are often used for estimation of biomaterials degradability.

Deionized water or phosphate buffer solution (PBS) is generally used for obtaining hydrolytic conditions in investigations of polymers degradation. According to Christenson et al. [70], the degradation of PURs in a solution of CoCl2/H2O2 effectively reflected the oxidation occurring in the living body. The similar changes in the structure of the polymers after one year implan‐ tation in the body of rats and after 24-day action of the oxidation mixture were observed. It has been found that the arrangement of CoCl2/H2O2 degraded the soft segments of the polyetherurethanes 17 times faster and the polycarbonate urethanes - 14 times [70]. Aliphatic PUR were also degraded in SBF and Ringer solution.


**Parameter [unit] PUR-2A-3 PUR-3A-1 PUR-3A-3 Blood sample**

/μl] 6.0 5.9 6.1 6.1 4.0-10.0

/ μl] 4.4 4.4 4.4 4.3 4.0-5.0

/μl] 255.5 253.4 246.8 247 140.0-400.0

MPV [fl] 9.5 11.3 10.7 9.4 7.0-12.0 APTT [RATIO] 31.3 36.5 29.4 29.8 26.0-37.0 FIBR [g/l] 3.2 1.2 3.5 3.4 1.5-4.5

The values of hematologic parameters before and after the incubation of PUR samples in blood were in reference ranges. Differences in comparison to the control probe were not observed that suggests the lack of hemolysis activated by polyurethane presence. Insignificant changes in platelet and fibrinogen concentration and in APPT during direct contact of blood with polymer samples suggested that polyurethanes based on synthetic poly([R,S]-3-hydroxybu‐

The influence of the surrounding environment on implanted material can be simulated using hydrolytic and oxidative solutions. Also, simulated body fluids (SBF) and Ringer solutions included ions that could be found in natural fluids are often used for estimation of biomaterials

Deionized water or phosphate buffer solution (PBS) is generally used for obtaining hydrolytic conditions in investigations of polymers degradation. According to Christenson et al. [70], the degradation of PURs in a solution of CoCl2/H2O2 effectively reflected the oxidation occurring in the living body. The similar changes in the structure of the polymers after one year implan‐ tation in the body of rats and after 24-day action of the oxidation mixture were observed. It has been found that the arrangement of CoCl2/H2O2 degraded the soft segments of the polyetherurethanes 17 times faster and the polycarbonate urethanes - 14 times [70]. Aliphatic

**Table 7.** Blood parameters after direct contact with PUR samples and those without contact.

HGB [g/dl] 12.6 12.7 12.6 12.2 12.0-16.0 HCT [%] 38.1 38.8 37.9 38.0 37.0-47.0 MCV [fl] 87.6 88.0 87.4 87.2 80.0-96.0 MCH [pg] 28.8 28.8 28.8 28.8 27.0-32.0 MCHC [g/dl] 32.9 32.7 33.0 33.0 31.0-36.0 RDW [%] 13.7 13.8 13.9 13.7 11.5-14.5

WBC [\*103

14 Thermoplastic Elastomers - Synthesis and Applications

RBC [\*106

PLT [\*103

tyrate) could be atrombogenic [65].

PUR were also degraded in SBF and Ringer solution.

*2.2.9. Degradability*

degradability.

**without PUR**

**Reference value**

**Table 8.** The weight changes of PUR samples after incubation (at 37°C) in phosphate buffer solution (PBS), oxidative solution (CoCl2/H2O2), simulated body fluids (SBF), and Ringer solution (Ringer) (results partially presented in [52, 54, 71]).

The susceptibility to hydrolytic and oxidative degradation of obtained PUR with synthetic poly([R,S]-3-hydroxybutyrate) indicated that these materials were more sensitive to the oxidative than hydrolytic conditions. Using an aliphatic diisocyanate in the synthesis (instead of aromatic) increased the susceptibility of PURs to degradation, especially in hydrolytic environments. More susceptible to degradation processes were PUR with PTMG than PCL in soft segment [71].

Introduction of R,S-PHB into the soft segments increased the rate of degradation in all investigated solutions. Aliphatic PURs based on R,S-PHB and PTMG appeared as the most sensitive to conditions of all degradative solutions (higher sample mass loss and molecular weight reduction were noticed) [54].

In some cases, after 36 weeks of incubation the sample mass did not change significantly or even increased. The observed molecular weight reduction after incubation of PURs based on PCL in phosphate buffer indicated that ester linkages were hydrolyzed but because of the insolubility of PCL products, they were not rinsed polymer bulk [54]. Mondal et al. [55] suggested that the degradation products could be retained in bulk films by hydrogen bonding, van der Waals force, polar interaction, etc.

Meanwhile, increasing of sample mass of PUR-3A-2 and PUR-3A-4 after incubation in SBF was probably the result of salts molecules trapping between the macrochains of the polymer network what influenced on the samples mass [52]. Moreover, according to microscope observations of polymer samples presented earlier presence of R,S-PHB in soft segments of PURs protected them against the salt sediments.

Degradability of PURs with R,S-PHB in soft segments could be also controlled by their mixing with PLA [66]. The presence of PLA in polyurethane blends accelerated their degradation in hydrolytic, trypsin, and lipase solutions. The significant reduction of molecular weight of polymer samples after incubation in phosphate buffer and the lack of mass changes after incubation in enzyme solutions suggested that polyurethanes and their blends were degraded via chemical hydrolysis. The investigations of morphology of the surface structure, which was changed after the incubation in both enzymes indicated that the enzymatic hydrolysis had been already initiated [66].

## *2.2.10. Electrospinning*

DSC and WAXS results indicated that similar PURs (with molar ratio of NCO:OH=2:1 in prepolymer) containing PCL in soft segments had higher ability for crystallization than those having PTMG in soft segments [53]. It was the reason why PURs containing PTMG and R,S-PHB in soft segments was chosen for electrospinning. Polymer appeared as spinnable in an electric field, with thermal stability (no phase transitions) in the temperature range up to 95°C. Electrospinning of polyether-esterurethane from hexafluoro-2-propanole solution resulted in the formation of fibers with an average diameter ca. 2 μm. [53].

## **3. Conclusion**

It could be stated that PURs based on synthetic poly([R,S]-3-hydroxybutyrate) displayed the properties appropriate for further investigations for medical applications such as degradable scaffolds. Properties of presented polyester- and polyester-etherurethanes suggest that they could be biocompatible, biostatic, and biodegradable under conditions of living body envi‐ ronment. It suggests also that aromatic diisocyanate may be successfully replaced by an aliphatic one. Incorporation of synthetic polyhydroxybutyrate into soft segments of PURs decreased their degree of crystallinity and increased degradability.

Using polycaprolactonediol for PUR synthesis is appropriate for the design of material undergoing slow and gradual degradation in living body. Higher oil sorption and faster rate of degradation of aliphatic PURs based on polyoxytetramethylenediol promote it for being used as biodegradable scaffolds with hydrophobic active substance.

## **Author details**

Joanna Brzeska

Address all correspondence to: j.brzeska@wpit.am.gdynia.pl

Gdynia Maritime University, Faculty of Entrepreneurship and Quality Science, Department of Chemistry and Industrial Commodity Science, Gdynia, Poland

## **References**

Degradability of PURs with R,S-PHB in soft segments could be also controlled by their mixing with PLA [66]. The presence of PLA in polyurethane blends accelerated their degradation in hydrolytic, trypsin, and lipase solutions. The significant reduction of molecular weight of polymer samples after incubation in phosphate buffer and the lack of mass changes after incubation in enzyme solutions suggested that polyurethanes and their blends were degraded via chemical hydrolysis. The investigations of morphology of the surface structure, which was changed after the incubation in both enzymes indicated that the enzymatic hydrolysis had

DSC and WAXS results indicated that similar PURs (with molar ratio of NCO:OH=2:1 in prepolymer) containing PCL in soft segments had higher ability for crystallization than those having PTMG in soft segments [53]. It was the reason why PURs containing PTMG and R,S-PHB in soft segments was chosen for electrospinning. Polymer appeared as spinnable in an electric field, with thermal stability (no phase transitions) in the temperature range up to 95°C. Electrospinning of polyether-esterurethane from hexafluoro-2-propanole solution resulted in

It could be stated that PURs based on synthetic poly([R,S]-3-hydroxybutyrate) displayed the properties appropriate for further investigations for medical applications such as degradable scaffolds. Properties of presented polyester- and polyester-etherurethanes suggest that they could be biocompatible, biostatic, and biodegradable under conditions of living body envi‐ ronment. It suggests also that aromatic diisocyanate may be successfully replaced by an aliphatic one. Incorporation of synthetic polyhydroxybutyrate into soft segments of PURs

Using polycaprolactonediol for PUR synthesis is appropriate for the design of material undergoing slow and gradual degradation in living body. Higher oil sorption and faster rate of degradation of aliphatic PURs based on polyoxytetramethylenediol promote it for being

Gdynia Maritime University, Faculty of Entrepreneurship and Quality Science, Department

the formation of fibers with an average diameter ca. 2 μm. [53].

decreased their degree of crystallinity and increased degradability.

used as biodegradable scaffolds with hydrophobic active substance.

Address all correspondence to: j.brzeska@wpit.am.gdynia.pl

of Chemistry and Industrial Commodity Science, Gdynia, Poland

been already initiated [66].

16 Thermoplastic Elastomers - Synthesis and Applications

*2.2.10. Electrospinning*

**3. Conclusion**

**Author details**

Joanna Brzeska


[24] Foster LJR, Tighe BJ. Centrifugally spun polyhydroxybutyrate fibres: Accelerated hy‐ drolytic degradation studies, Polymer Degradation and Stability. 2005;87:1–10 DOI: 10.1016/j.polymdegradstab.2003.11.012.

[13] El-Sayed, El Gabry LK, Allam OG. Application of prepared waterborne polyurethane extended with chitosan to impart antibacterial properties to acrylic fabrics. J Mater

[14] Khandwekar AP, Doble M. Physicochemical characterisation and biological evalua‐ tion of polyvinylpyrrolidone-iodine engineered polyurethane (Tecoflex). J Mater Sci:

[15] Park D, Larson AM, Klibanov AM, Wang Y. Antiviral and Antibacterial Polyur‐ ethanes of Various Modalities. Appl Biochem Biotechnol. 2013;169:1134–1146. DOI:

[16] Xu H, Chang J, Chen Y, Fan H, Shi B. Asymmetric polyurethane membrane with in‐ flammation responsive, antibacterial activity for potential wound dressing applica‐

[17] Akbarian M, Olya ME, Ataeefard M, Mahdavianc M. The influence of nanosilver on thermal and antibacterial properties of a 2 K waterborne polyurethane coating. Prog‐ ress in Organic Coatings. 2012;75:344–348. DOI.org/10.1016/j.porgcoat.2012.07.017. [18] Wang J., Sun P., Zheng Z., Wang F. Wang X. Glutathione-responsive biodegradable polyurethanes based on dithiodiundecanol. Polymer Degradation and Stability.

[19] Da Silva GR, da Silva-Cunha A Jr, Francine Behar-Cohen F, Ayres E, Oréfic RL. Bio‐ degradable polyurethane nanocomposites containing dexamethasone for ocular route. Materials Science and Engineering. 2011;C31:414–422. DOI: 10.1016/j.msec.

[20] Saralegi A, Gonzalez ML, Valea A, Eceiza A, Corcuera MA. The role of cellulose nanocrystals in the improvement of the shape-memory properties of castor oil-based segmented thermoplastic polyurethanes. Composites Science and Technology. 2014;

[21] Chan-Chan LH, Tkaczyk C, Vargas-Coronado RF, Cervantes-Uc JM, Tabrizian M, Cauich-Rodriguez JV. Characterization and biocompatibility studies of new degrada‐ ble poly(urea)urethanes prepared with arginine, glycine or aspartic acid as chain ex‐ tenders. J Mater Sci: Mater Med. 2013;24:1733–1744. DOI: 10.1007/s10856-013-4931-4.

[22] Jia L, Prabhakaran MP, Qin X, Kai D, Ramakrishna S. Biocompatibility evaluation of protein-incorporated electrospun polyurethane-based scaffolds with smooth muscle cells for vascular tissue engineering. J Mater Sci. 2013;48:5113–5124. DOI: 10.1007/

[23] Cyras VP, Soledad CM, Analı´ V. Biocomposites based on renewable resource: Ace‐ tylated and non acetylated cellulose cardboard coated with polyhydroxybutyrate.

Polymer. 2009;50:6274–6280. DOI: 10.1016/j.polymer.2009.10.065.

Sci: Mater Med. 2010;21:507–514. DOI: 10.1007/s10856-009-3900-4.

Mater Med. 2011;22:1231–1246. DOI:10.1007/s10856-011-4285-8.

tion. J Mater Sci. 2013;48:6625–6639. DOI: 10.1007/s10853-013-7461-z.

2012;97:2294–2300. DOI.org/10.1016/j.polymdegradstab.2012.07.041.

92:27–33. DOI.org/10.1016/j.compscitech.2013.12.001.

10.1007/s12010-012-9999-7.

18 Thermoplastic Elastomers - Synthesis and Applications

2010.10.019.

s10853-013-7359-9.


[48] Loh XJ, Tan KK, Li X, Li J. The in vitro hydrolysis of poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] and poly(ethylene glycol). Biomaterials. 2006;27:1841–1850. DOI: 10.1016/j.biomaterials.2005.10.038.

[36] Hong SG, Hsu HW, Ye MT. Thermal properties and applications of low molecular weight polyhydroxybutyrate. J Therm Anal Calorim. 2013;111:1243–1250. DOI:

[37] Hong SG, Gau TK, Huang SC. Enhancement of the crystallization and thermal stabil‐ ity of polyhydroxybutyrate by polymeric additives. J Therm Anal Calorim.

[38] Arslan H, Adamus G, Hazer B, Kowalczuk M. electrospray ionisation tandem mass spectrometry of poly[(R,S)-3-hydroxybutanoic acid] telechelics containing primary

[39] Jedliński Z, Kurcok P, Kowalczuk M. Method of synthesis of amorphous

[40] Piddubnyak V, Kurcok P, Matuszowicz A, Głowala M, Fiszer-Kierzkowska A, Jedliń‐ ski Z et al. Oligo-3-hydroxybutyrates as potential carriers for drug delivery. Biomate‐

[41] Brzeska J, Dacko P, Janeczek H, Janik H, Rutkowska M, Sikorska W, et al. Synthesis, properties and applications of new (bio)degradable polyester urethanes (in Polish).

[42] Kunze C, Bernd HE, Androsch R, Nischan C, Freier T, Kramer S, et al. In vitro and in vivo studies on blends of isotactic and atactic poly(3-hydroxybutyrate) for develop‐ ment of dura substitute material. Biomaterials. 2006;27:192–201. DOI: 10.1016/

[43] Freier T, Kunze C, Nischan C, Kramer S, Sternberg K, Saß M, et al. In vitro and in vivo degradation studies for development of biodegradable patch based on poly(3-

[44] Cebulska A, Jedliński Z. Preparation of spherical particles of 3-hydroxybutyric acid

[45] Aziz MSA, Naguib HF, Saad GR. Non-isothermal crystallization kinetics of bacterial poly(3-hydroxybutyrate) in poly(3-hydroxybutyrate-co-butylene adipate) urethanes. Thermochimica Acta. 2014;591:130–139. dx.doi.org/10.1016/j.tca.2014.07.026

[46] Pan J, Li G, Chen Z, Chen X, Zhu W, Xu K. Alternative block polyurethanes based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(ethylene glycol). Biomateri‐

[47] Ou W, Qiu H, Chen Z, Xu K. Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrateco-4-hydroxybutyrate) copolymers. Biomaterials.

als. 2009;30:2975–2984. doi:10.1016/j.biomaterials.2009.02.005.

2011;32:3178–3188. DOI: 10.1016/j.biomaterials.2011.01.031.

hydroxy end groups. Rapid Commun. Mass Spectrom. 1999;13:2433–2438.

poly([R,S]-3-hydroxybutyric acid), Polish Pat Appl P-339795, 2000.

rials. 2004;25:5271–5279. DOI: 10.1016/j.biomaterials.2003.12.029.

hydroxybutyrate). Biomaterials. 2002;23:2649–2657.

oligomer (in Polish). Polimery. 2006;6:436–441.

10.1007/s10973-012-2503-3.

20 Thermoplastic Elastomers - Synthesis and Applications

Polimery. 2014;59(5):363–371.

j.biomaterials.2005.05.095.

0040-6031..

2011;103:967–975. DOI 10.1007/s10973-010-1180-3.


[59] Bayarı S, Severcan F. FTIR study of biodegradable biopolymers: P(3HB), P(3HBco4HB) and P(3HB-co-3HV). Journal of Molecular Structure. 2005;744-747:529–534.

[60] Yilgor I, Yilgor E, Guler IG, Ward TC, Wilkes GL. FTIR investigation of the influence of diisocyanate symmetry on the morphology development in model segmented pol‐

[61] Brzeska J, Dacko P, Janeczek H, Kowalczuk M, Janik H, Rutkowska M. The influence of synthetic polyhydroxybutyrate on selected properties of novel polyurethanes for medical applications. Part I. Polyurethanes with aromatic diisocyanates in hard seg‐

[62] Brzeska J, Dacko P, Janeczek H, Kowalczuk M, Janik H, Rutkowska M. The influence of synthetic polyhydroxybutyrate on selected properties of novel polyurethanes for medicine B. Polyurethanes with aliphatic diisocyanate in hard segment (in Polish).

[63] Janik H. Supermolecular structure and selected properties of branched and crosslinked poly(esterurethanes), poly(etherurethanes) and poly(ureauretanes) formed re‐ actively (in Polish). Zeszyty Naukowe Politechniki Gdańskiej. 2005. 599.

[64] Brzeska J. The influence of synthetic polyhydroxybutyrate on properties of new poly‐ urethanes for medical application [dissertation] (in Polish). Gdynia Maritime Univer‐

[65] Brzeska J, Janik H, Kowalczuk M, Rutkowska M. Preliminary investigations of bio‐ compatibility of polyurethanes based on synthetic polyhydroxybutyrate, Engineer‐

[66] Brzeska J, Heimowska A, Sikorska W, Jasinska-Walc L, Kowalczuk M, Rutkowska M. Degradation of polyurethane/polylactide blends. International Journal of Polymer

[67] Jonquières A, Clément R, Lochon P. Permeability of block copolymers to vapours

[68] Brzeska J, Janik H, Kowalczuk M, Rutkowska M. Influence of polyurethanes based on synthetic poly([R,S]-3-hydroxybutyrate) on microorganisms growth. Engineering

[69] Brzeska J, Kowalczuk M, Janik H, Rutkowska M. The properties of polyurethanes based on synthetic polyhydroxybutyrate for medical application. Joint Proceedings

[70] Christenson EM, Patel S, Anderson JM, Hiltner A. Enzymatic degradation of poly(ether urethane) and poly(carbonate urethane) by cholesterol esterase. Biomate‐

and liquids, Progress in Polymer Science. 2002;27:1803–1877.

Gdynia Maritime University-Bremerhaven. 2012;74:5–14.

rials. 2006;27:3920–3926. DOI:10.1016/j.biomaterials.2006.03.012.

yurethanes. Polymer. 2006;47:4105–4114. DOI: 10.1016/j.polymer.2006.02.027.

DOI:10.1016/j.molstruc.2004.12.029.

22 Thermoplastic Elastomers - Synthesis and Applications

ments (in Polish). Polimery. 2010;1:44–47.

Wydawnictwo Politechniki Gdańskiej. Gdańsk.

ing of Biomaterials. 2011;106-108(XIV):65–72.

of Biomaterials. 2011;106-108(XIV):73–78.

Polimery. 2011;1:27–34.

isty:2010. 189

Science. Forthcoming.

**Synthesis and Properties of Multiblock Terpoly(Ester-Aliphatic-Amide) and Terpoly(Ester-Ether-Amide) Thermoplastic Elastomers with Various Chemical Compositions of Ester Block**

Joanna Rokicka and Ryszard Ukielski

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/61215

## **Abstract**

Two series of thermoplastic elastomers with various chemical compositions of ester block were prepared via the reaction of α,ω-dicarboxylic oligo(laurolactam) (PA12, Mw≈2000 g/mol) with oligo(oxytetramethylene)diol (PTMO, Mw≈1000 g/mol) or linoleic alcohol dimer (DLAol) and with dimethyl terephthalate and a low molecular weight glycol (forming during the synthesis of the ester block). The degree of polycondensation (DPGT) of poly(multi-methylene terephtalate) equals to DPGT=2. The influence of the number of carbons separating the terephtalate groups, as well as the effect of *meta*- or *para*- positions of the ester groups in the benzene ring of other blocks, on the synthesis, properties and structure of these elastomers have been evaluated. A nuclear magnetic resonance spectroscopy to carbon (13C NMR) and Fourier transform infrared spectroscopy (FT-IR) were used to confirm their assumed chemical structure. The influence of chemical compositions of ester block on the functional properties and on the values of phase transition temperatures of the products have been determined. The thermal properties and the phase separation of obtained systems were defined by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), wide-angle x-ray diffraction (WAXS) and other standard physical methods. The mechanical and elastic properties of obtained polymers were evaluated.

**Keywords:** Poly(ester-ether-amide), poly(ester-aliphatic-amide), multiblock terpoly‐ mers, elastomers, phase structure

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **1. Introduction**

A growing demand for polymeric materials in the packaging, sport, automotive, and medicine industries stimulates the search for innovative materials with thermal and mechanical properties individually tailored for a given field. Depending on the application, these materials have to be characterized, among others, by their resistance to chemical, mechanical, or biological factors. These requirements may be successfully satisfied by the thermoplastic multiblock elastomer (TPE).

They combine the end-use physical properties of vulcanized rubbers with the easy processing of thermoplastic [1–5]. The properties of TPEs are influenced by an appropriate phase structure and its thermal reproducibility in the heating-cooling cycle, functional qualities (large, reversible deformations) and the processing properties (possibility of multiple melting and solidifications). TPEs are considered as polymeric materials, in which, as a result of the phase separation, at least two phases (soft and hard) are distinguished, which must be thermody‐ namically immiscible to prevent the interpenetration. Hence, these are plastics possessing at least the two values of the physical transition temperatures, i.e., glass transition temperature Tg and melting point temperature Tm or Tg1 and Tg2. These two temperatures determine the points at which the particular elastomer goes through transitions in its physical properties [6]. There are three distinct regions:


Some of multiblock copolymers that have a heterophase internal structure are classified as the group of thermoplastic elastomers. Their macromolecule must contain two types of chain segments: amorphous, referred to as soft blocks, and hard blocks, which are mostly crystal‐ line [9–12]. These blocks differ considerably in their physical and chemical properties. The soft blocks, which are capable of forming a soft-phase matrix, provides the elastomeric character, susceptibility to hydrolysis, and behavior of copolymer at low temperatures; while the hard segments determine processability, mechanical properties, hardness, and high temperature resistance. Hard segments are able to form intermolecular association with other hard blocks and these blocks form the domains of hard phase and are immersed in a soft-phase matrix. To classify the block elastomers to TPEs, their internal structure must comply with strict condi‐ tions. The soft phase should exhibit a relatively small elastic modulus, relatively low glass transition temperature, and a lower density. Moreover, these blocks should ensure weak intermolecular interactions and a large capability for motion and rotation of short sequences of chains. The hard phase must possess a relatively large elasticity modulus, high glass transi‐ tion temperature or melting point, and high density. The segments that build this phase must

exhibit a tendency to aggregate with the same kind of segments. This aggregation leads to the thermally reversible "physical cross-linking", which is stabilized by the van der Waals forces, high cohesive energy, hydrogen bonds, ionic bonds, the polar and dispersive interactions, or the ability to crystallization. The intermolecular interactions of rigid blocks affect the stabiliza‐ tionofthephase structureofthewholepolymeric system.Thehardsegmentsmusthave a larger cohesive energy than the flexible segments and hence, a higher thermodynamic potential. The potential difference is a force that induces and stabilizes a heterophase structure [13–17].

The block copolymer will exhibit characteristics of a good elastomer if it complies with five inseparable conditions:


The TPE properties are a result of the combination of the individual features of the respective blocks, hence a change of their chemical structure or their relative mass fraction, enables a modification of the macromolecule properties in the desired directions [18–25].

In the present chapter, the synthesis of multiblock thermoplastic elastomers and the relation‐ ship between the chemical structure of soft block and the properties in connection with the phase structure of terpolymers are described. The following terpolymers were selected for this research study:


## **2. Experimental part**

## **2.1. Materials**

**1. Introduction**

multiblock elastomer (TPE).

26 Thermoplastic Elastomers - Synthesis and Applications

There are three distinct regions:

is characteristic for TPEs;

becomes a viscous fluid [7, 8].

the material is stiff and brittle;

A growing demand for polymeric materials in the packaging, sport, automotive, and medicine industries stimulates the search for innovative materials with thermal and mechanical properties individually tailored for a given field. Depending on the application, these materials have to be characterized, among others, by their resistance to chemical, mechanical, or biological factors. These requirements may be successfully satisfied by the thermoplastic

They combine the end-use physical properties of vulcanized rubbers with the easy processing of thermoplastic [1–5]. The properties of TPEs are influenced by an appropriate phase structure and its thermal reproducibility in the heating-cooling cycle, functional qualities (large, reversible deformations) and the processing properties (possibility of multiple melting and solidifications). TPEs are considered as polymeric materials, in which, as a result of the phase separation, at least two phases (soft and hard) are distinguished, which must be thermody‐ namically immiscible to prevent the interpenetration. Hence, these are plastics possessing at least the two values of the physical transition temperatures, i.e., glass transition temperature Tg and melting point temperature Tm or Tg1 and Tg2. These two temperatures determine the points at which the particular elastomer goes through transitions in its physical properties [6].

**•** at very low temperatures, below the Tg of the soft phase, in which both phases are hard, so

**•** between the Tg of the soft phase and the Tm of the hard phase, in which material is soft and elastic, resembling a conventional vulcanized rubber. In these temperature range a modulus of elasticity stays relatively constant and this region is referred as "rubbery plateau" which

**•** above the Tm of the hard phase, where the hard phase softens and melts and the material

Some of multiblock copolymers that have a heterophase internal structure are classified as the group of thermoplastic elastomers. Their macromolecule must contain two types of chain segments: amorphous, referred to as soft blocks, and hard blocks, which are mostly crystal‐ line [9–12]. These blocks differ considerably in their physical and chemical properties. The soft blocks, which are capable of forming a soft-phase matrix, provides the elastomeric character, susceptibility to hydrolysis, and behavior of copolymer at low temperatures; while the hard segments determine processability, mechanical properties, hardness, and high temperature resistance. Hard segments are able to form intermolecular association with other hard blocks and these blocks form the domains of hard phase and are immersed in a soft-phase matrix. To classify the block elastomers to TPEs, their internal structure must comply with strict condi‐ tions. The soft phase should exhibit a relatively small elastic modulus, relatively low glass transition temperature, and a lower density. Moreover, these blocks should ensure weak intermolecular interactions and a large capability for motion and rotation of short sequences of chains. The hard phase must possess a relatively large elasticity modulus, high glass transi‐ tion temperature or melting point, and high density. The segments that build this phase must

The following substrates were used: dimethyl terephthalate (DMT) - Chemical Plant "Elana", ethylene glycol (2G), 1,3-propanediol (3G), 1,4-butanediol (4G), 1,5-penatnediol (5G), 1,6hexanediol (6G) - Sigma-Aldrich, poly(oxytetramethylene)diol with molecular weight 1000 g/ mol (PTMO) - Du Pont, linoleic alcohol dimer (DLAol) - Croda, a titanate catalyst (TiO2/SiO2) - Sachtleben Chemic GmgH, thermal stabilizer (Irganox 1010) - Ciba Geigy, dodecano-12 lactam, sebacic acid - Aldrich Chemie. The lactam and the dicarboxilic acid are the substrates prepared in our laboratory: α,ω-dicarboxilic oligo(laurolactam) (PA12) with the number average molecular weight 2000 g/mol [26, 27].

## **2.2. Synthesis of oligoamide blocks**

The synthesis of oligoamides with molecular weight 2000 g/mol bi-ended with carboxylic groups was carried out.

Synthesis was carried out in a cylindrical shape with conical bottom 6-dm3 autoclave made of stainless steel. The ratio of height to reactor diameter is h:d=3.5. The heating system comprise a set of three resistance heaters enabling control of temperature in the range 20°C–400°C. The regulators are controlled by Fe-constantan thermocouples and Pt-100 thermoresistors.

A suitable amount of laurolactam and sebacic acid, which was a stabilizator of molecular weight of the obtained oligoamides, was placed in the reactor. A small dose of water and phosphoric acid was added to simplify the initiation of the reaction. Before the synthesis, the autoclave was purged three times with nitrogen at the pressure of 0.5 MPa to gain an oxygenfree reaction environment. After that, the reaction mixture was kept in the reactor under a pressure of 0.1 MPa and then heated to a temperature of 300°C. A pressure would not exceed 1.6 MPa. The pressure was controlled by the removal of water vapor that contained a small amount of amide di- and trimers. This pressure stage of the reaction lasted 5 h. In the last half hour of this stage, the temperature raised to 305°C. Then, the pressure was reduced during 0.5 h to atmospheric pressure without decreasing the temperature. The pressureless stage (polycondensation) was carried out for 5 h under a flow of nitrogen. After the reaction was completed, the obtained oligoamide was extruded by compressed nitrogen into a tube with water that was vigorously stirring with bubbling air. To extract the residual by-products and unreacted lactam the finished product was rinsed three times with boiling water and then with distilled water. After drying in air and in a vacuum dryer at the temperature 60°C, the oligoamide was grounded and characterized.

## **2.3. Synthesis of multiblock thermoplastic elastomers**

Synthesis of block terpolymers proceeded in the two stages. The first stage was the transes‐ terification reaction of dimethyl terephthalete with glycol leading to the formation of polyester and the release of methanol and the esterification (in a separate reactor) of α,ω-dicarboxylic oligo(laurolactam) with oligo(oxytetramethylene)diol or linoleic alcohol dimer (by-product is water) in the presence of catalyst. From the respective amounts of methanol and water, it was concluded that the conversation in the transesterification reaction was 95% and the degree of esterification was 90% (degrees was expressed as the weight ratios of the released methanol or water to the respective stoichiometric amounts of these products). The second stage of the process comprises the specific condensation polymerization of mixed intermediates obtained in the first stage of synthesis. The course and parameters of synthesis is presented in Figure 1. Synthesis and Properties of Multiblock Terpoly (Ester-Aliphatic-Amide) and… http://dx.doi.org/10.5772/61215 29

**Figure 1.** Structure flow chart.

hexanediol (6G) - Sigma-Aldrich, poly(oxytetramethylene)diol with molecular weight 1000 g/ mol (PTMO) - Du Pont, linoleic alcohol dimer (DLAol) - Croda, a titanate catalyst (TiO2/SiO2) - Sachtleben Chemic GmgH, thermal stabilizer (Irganox 1010) - Ciba Geigy, dodecano-12 lactam, sebacic acid - Aldrich Chemie. The lactam and the dicarboxilic acid are the substrates prepared in our laboratory: α,ω-dicarboxilic oligo(laurolactam) (PA12) with the number

The synthesis of oligoamides with molecular weight 2000 g/mol bi-ended with carboxylic

Synthesis was carried out in a cylindrical shape with conical bottom 6-dm3 autoclave made of stainless steel. The ratio of height to reactor diameter is h:d=3.5. The heating system comprise a set of three resistance heaters enabling control of temperature in the range 20°C–400°C. The regulators are controlled by Fe-constantan thermocouples and Pt-100 thermoresistors.

A suitable amount of laurolactam and sebacic acid, which was a stabilizator of molecular weight of the obtained oligoamides, was placed in the reactor. A small dose of water and phosphoric acid was added to simplify the initiation of the reaction. Before the synthesis, the autoclave was purged three times with nitrogen at the pressure of 0.5 MPa to gain an oxygenfree reaction environment. After that, the reaction mixture was kept in the reactor under a pressure of 0.1 MPa and then heated to a temperature of 300°C. A pressure would not exceed 1.6 MPa. The pressure was controlled by the removal of water vapor that contained a small amount of amide di- and trimers. This pressure stage of the reaction lasted 5 h. In the last half hour of this stage, the temperature raised to 305°C. Then, the pressure was reduced during 0.5 h to atmospheric pressure without decreasing the temperature. The pressureless stage (polycondensation) was carried out for 5 h under a flow of nitrogen. After the reaction was completed, the obtained oligoamide was extruded by compressed nitrogen into a tube with water that was vigorously stirring with bubbling air. To extract the residual by-products and unreacted lactam the finished product was rinsed three times with boiling water and then with distilled water. After drying in air and in a vacuum dryer at the temperature 60°C, the

Synthesis of block terpolymers proceeded in the two stages. The first stage was the transes‐ terification reaction of dimethyl terephthalete with glycol leading to the formation of polyester and the release of methanol and the esterification (in a separate reactor) of α,ω-dicarboxylic oligo(laurolactam) with oligo(oxytetramethylene)diol or linoleic alcohol dimer (by-product is water) in the presence of catalyst. From the respective amounts of methanol and water, it was concluded that the conversation in the transesterification reaction was 95% and the degree of esterification was 90% (degrees was expressed as the weight ratios of the released methanol or water to the respective stoichiometric amounts of these products). The second stage of the process comprises the specific condensation polymerization of mixed intermediates obtained in the first stage of synthesis. The course and parameters of synthesis is presented in Figure 1.

average molecular weight 2000 g/mol [26, 27].

oligoamide was grounded and characterized.

**2.3. Synthesis of multiblock thermoplastic elastomers**

**2.2. Synthesis of oligoamide blocks**

28 Thermoplastic Elastomers - Synthesis and Applications

groups was carried out.

Preparation of terpolymers relies on the replacement in the poly(multi-methylene terephtha‐ late) macromolecule (xGT), a certain part of fragments originated from the terephthalic acid by the dicarboxylic oligoamide block, which was derived from glycol by the oligoetherdiol or alifatic block (Figure 2).

**Figure 2.** Multi-methylene terephthalate modification.

The previous investigations carried out by Ukielski [28–30] have demonstrated that the molar ratio of PTMO with molecular weight 1000 g/mole to PA12 with molecular weight 2000 g/mole should be ranged between 2 and 3.5. This determines a relatively small fraction of the xGT sequence in the soft phase, large degrees of separation of both soft and hard phase and comparable fraction of the respective blocks in the interphase. Based on the results of previous works, the molar ratio of PTMO/PA12=3 was assumed for further studies. A two series of terpolymers composed of the blocks PTMO or DLAol and PA12 with the constant molar weight amounting to respectively, 1000 g/mole, 570 g/mole and 2000 g/mol and xGT block, with constant degree of polycondensation amounting DPxGT=2, which is formed during the synthe‐ sis, were prepared. The series differ in a chemical structure of the ester block. The molar ratio and weight ratios of reagent used for the synthesis were presented in Table 1.


**Table 1.** The composition of terpolymers with constant molecular weights of PA12=2000 g/mole and PTMO=1000 g/ mole; DPxGT=2.

## **3. Results and discussion**

## **3.1. Properties of α,ω-dicarboxylic oligoamides**

Assumed molecular weight of the oligoamide was 2000 g/mole. The difference between the molecular weight values, calculated from the amounts of the carboxylic groups and the assumed theoretical values do not exceed 2.5% of the experimental error, which supports the correctness of the experimental assumptions. The melting temperature values of the PA12 oligoamides are lowers than the melting temperature of the polyamide 12, which is 179°C.

Usage of sebacic acid as the molecular weight stabilizer leads to dicarboxylic oligoamids. Obtained oligoamids had coherent with assumed molecular weight values, didn't contain amid groups, and may be used as hard block in various types of thermoplastic multiblock elastomers. Some properties of the obtained α,ω-dicarboxilic oligoamides are presented in Table 2.


[-COOH] – the concentration of carboxyl groups, [-NH2] – the concentration of amino groups, Mn - average molecular weight, Tm – melting temperature range determined by means of the Boethius microscope

**Table 2.** Properties of obtained oligoamides.

## **3.2. Properties of TPE**

comparable fraction of the respective blocks in the interphase. Based on the results of previous works, the molar ratio of PTMO/PA12=3 was assumed for further studies. A two series of terpolymers composed of the blocks PTMO or DLAol and PA12 with the constant molar weight amounting to respectively, 1000 g/mole, 570 g/mole and 2000 g/mol and xGT block, with constant degree of polycondensation amounting DPxGT=2, which is formed during the synthe‐ sis, were prepared. The series differ in a chemical structure of the ester block. The molar ratio

**Sample Glycol Soft block msoft mPA12 mDMT mxG wPTMO wxGT wPA12 Series** 1 2G PTMO 3 1 5 9 0,520 0,133 0,347 I

6 2G DLAol 3 1 5 9 0,382 0,172 0,447 II

 3G PTMO 3 1 5 9 0,515 0,141 0,343 4G PTMO 3 1 5 9 0,510 0,150 0,340 5G PTMO 3 1 5 9 0,505 0,158 0,337 6G PTMO 3 1 5 9 0,501 0,166 0,334

 3G DLAol 3 1 5 9 0,377 0,182 0,441 4G DLAol 3 1 5 9 0,373 0,192 0,436 5G DLAol 3 1 5 9 0,368 0,201 0,430 6G DLAol 3 1 5 9 0,364 0,211 0,425

**Table 1.** The composition of terpolymers with constant molecular weights of PA12=2000 g/mole and PTMO=1000 g/

Assumed molecular weight of the oligoamide was 2000 g/mole. The difference between the molecular weight values, calculated from the amounts of the carboxylic groups and the assumed theoretical values do not exceed 2.5% of the experimental error, which supports the correctness of the experimental assumptions. The melting temperature values of the PA12 oligoamides are lowers than the melting temperature of the polyamide 12, which is 179°C.

Usage of sebacic acid as the molecular weight stabilizer leads to dicarboxylic oligoamids. Obtained oligoamids had coherent with assumed molecular weight values, didn't contain amid groups, and may be used as hard block in various types of thermoplastic multiblock elastomers. Some properties of the obtained α,ω-dicarboxilic oligoamides are presented in

m – molar ratio, w – weight fraction

30 Thermoplastic Elastomers - Synthesis and Applications

**3. Results and discussion**

**3.1. Properties of α,ω-dicarboxylic oligoamides**

mole; DPxGT=2.

Table 2.

and weight ratios of reagent used for the synthesis were presented in Table 1.

The number of carbons x separating the terephthalate groups in the ester block of TPEs influences all their properties, which were presented in Table 3.


[η] – limiting viscosity number, H – hardness, pH2O and pbenzene – absorbability of water and benzene, respectively, σ – tensile strength, E – the Young module, ε – elongation at break, T<sup>m</sup> i ,Tm e - initial and end of melting point

**Table 3.** The properties of terpolymer elastomers TPE with variable chemical structure of ester block.

TPEs have the satisfactory molecular weights and good mechanical properties when the values of their limiting viscosity numbers are larger than [η]>1.25 dL/g. The [η] values of obtained polymers have proved that they are composed of the macromolecules with satisfactory molecular weights. The ability to swell depends on the polarity of the solvent and the chemical structure of the polymer macromolecule. Swelling occurs only in the amorphous structural zones of the terpolymer. It is therefore a measure of the quality and content of the continuous phase. As a physical phenomenon indicates an internal cross-linking of the polymer and describes its physical structure. Absorbability increases with increasing mobility of the macromolecules and decreases with an increase in cohesive energy between them. The obtained results of swelling in water indicate for a hydrophobic character of all the prepared polymers. The swelling does not exceed 4%, which indicates the water penetration in the amorphous phase of polymer only in a slight degree. An increase in the number of carbons separating the terephthalate groups in the ester block of TPEEAs causes an increase of absorbability of benzene and decrease of hardness, due to an increase in amorphous phase content. Flexible blocks create more and better polymer matrix and the content of crystalline phase decreases. It results in the relaxation of the structure and distance from other polymer macromolecules, thus easier benzene penetration into the material and less rigidity.

## **3.3. Chemical structure of TPEs**

The FT-IR spectra [31, 32] of terpolymers selected from each series are shown in Figure 3 and 4. Obtained copolymers had all characteristic bands for esters, aliphates or ether, and amides, which are presented in Table 4.

**Figure 3.** FT-IR spectra for terpolymer 3GT-DLAol-PA12.

Synthesis and Properties of Multiblock Terpoly (Ester-Aliphatic-Amide) and… http://dx.doi.org/10.5772/61215 33

**Figure 4.** FT-IR spectra for terpolymer 3GT-PTMO-PA12.

zones of the terpolymer. It is therefore a measure of the quality and content of the continuous phase. As a physical phenomenon indicates an internal cross-linking of the polymer and describes its physical structure. Absorbability increases with increasing mobility of the macromolecules and decreases with an increase in cohesive energy between them. The obtained results of swelling in water indicate for a hydrophobic character of all the prepared polymers. The swelling does not exceed 4%, which indicates the water penetration in the amorphous phase of polymer only in a slight degree. An increase in the number of carbons separating the terephthalate groups in the ester block of TPEEAs causes an increase of absorbability of benzene and decrease of hardness, due to an increase in amorphous phase content. Flexible blocks create more and better polymer matrix and the content of crystalline phase decreases. It results in the relaxation of the structure and distance from other polymer

macromolecules, thus easier benzene penetration into the material and less rigidity.

The FT-IR spectra [31, 32] of terpolymers selected from each series are shown in Figure 3 and 4. Obtained copolymers had all characteristic bands for esters, aliphates or ether, and amides,

**3.3. Chemical structure of TPEs**

32 Thermoplastic Elastomers - Synthesis and Applications

which are presented in Table 4.

**Figure 3.** FT-IR spectra for terpolymer 3GT-DLAol-PA12.


**Table 4.** Wavenumbers and assignments of FT-IR band exhibited by obtained terpolymers.

Chemical structure of new materials was also verified with 13C NMR spectroscopy [31–34] and the results with peak assignments are presented in Figures 5 and 6. Analysis of the 13C NMR spectra showed the presence of all characteristic groups present in the esters, ethers or fatty acids, and amides. Signals are noted in the range 26.89–218.53 ppm and their interpretation are detailed in Table 5.

**Figure 5.** 13C NMR spectra of terpolymer 3GT-PTMO-PA12.

On the 13C NMR spectrum the peak presence at 39.56 ppm indicates that amide block is built into copolymer macromolecule.

13C NMR and FT-IR analysis confirmed the assumed chemical structure of terpoly(ester-etheramides) and terpoly(ester-aliphatic-amides). However, one should bear in mind that the terpoly(ester-ether-amide)s and terpoly(ester-aliphatic-amide)s are random block polymers.

#### Synthesis and Properties of Multiblock Terpoly (Ester-Aliphatic-Amide) and… http://dx.doi.org/10.5772/61215 35


Chemical structure of new materials was also verified with 13C NMR spectroscopy [31–34] and the results with peak assignments are presented in Figures 5 and 6. Analysis of the 13C NMR spectra showed the presence of all characteristic groups present in the esters, ethers or fatty acids, and amides. Signals are noted in the range 26.89–218.53 ppm and their interpretation

On the 13C NMR spectrum the peak presence at 39.56 ppm indicates that amide block is built

13C NMR and FT-IR analysis confirmed the assumed chemical structure of terpoly(ester-etheramides) and terpoly(ester-aliphatic-amides). However, one should bear in mind that the terpoly(ester-ether-amide)s and terpoly(ester-aliphatic-amide)s are random block polymers.

are detailed in Table 5.

34 Thermoplastic Elastomers - Synthesis and Applications

**Figure 5.** 13C NMR spectra of terpolymer 3GT-PTMO-PA12.

into copolymer macromolecule.


**Table 5.** Chemical shifts (ppm) of terpoly(ester-ether-amides) and terpoly(ester-aliphatic-amides).

### **3.4. Mechanical properties**

The ability of instant recovery after the deformation is expressed by the elastic elongation(εs) and the area A, which is proportional to the dissipated elastic energy. It is a measure of the quality of the spatial network of the elastomer. High elastic elongation (εhs) and the area B, which is proportional to the dissipated energy, characterize the ability of a material to have delayed recovery after deformation. It is a measure of the quality of the continuous phase capable of viscoelastic response. Permanent set (εps) corresponds to the irreversible changes that have occurred in the material under the stress, most likely related to the change in the spatial distribution of domains. The area C is proportional to the accumulated energy. Received two types of mechanical hysteresis loops. The first type was obtained by stretching a terpoly‐ mer sample from 10% to 100% at elongation growing by 10% (Figure 7). The second one was obtained by stretching at constant elongation of 100% (Figure 8).

**Figure 7.** Mechanical hysteresis loops at elongation growing by 10% of the terpoly(ester-aliphatic-amide).

**Figure 8.** Mechanical hysteresis loops at a constant elongation of 100% of terpoly(ester-aliphatic-amide) and terpoly(es‐ ter-ether-amide), where the ester block was 5GT: εs – elastic elongation, εhs – delayed high-elastic elongation, εps – permanent set, A – area proportional to the dissipated elastic energy, B – area proportional to the dissipated high-elas‐ tic energy, C – area proportional to the accumulated energy.

In both series, the best mechanical properties have the terpolymer with the number x=4, whereas the best elastic residues exhibit terpolymers with x=5. Better mechanical properties, but worst elastic residues have terpolymers where the amorphous phase is DLAol (series II). This is probably due to the lower weight content of flexible blocks in the terpolymers. Terpol‐ ymers of this series, similar to PEE and PEA, exhibit a large part of energy accumulated during the first cycle of elongation. The probable cause is the strong interactions at the domain-matrix contact in these materials, due to hydrogen bonds, Van der Waals forces, or through Chain foldings. The mechanical hysteresis loops of terpoly(ester-ether-amide)s (series I) demonstrate that there is in these materials a small energy accumulation in the first cycle. Therefore, they are elastomers with a better mechanical shape memory than terpoly(ester-aliphatic-amide).

## **3.5. WAXS analysis**

**3.4. Mechanical properties**

36 Thermoplastic Elastomers - Synthesis and Applications

The ability of instant recovery after the deformation is expressed by the elastic elongation(εs) and the area A, which is proportional to the dissipated elastic energy. It is a measure of the quality of the spatial network of the elastomer. High elastic elongation (εhs) and the area B, which is proportional to the dissipated energy, characterize the ability of a material to have delayed recovery after deformation. It is a measure of the quality of the continuous phase capable of viscoelastic response. Permanent set (εps) corresponds to the irreversible changes that have occurred in the material under the stress, most likely related to the change in the spatial distribution of domains. The area C is proportional to the accumulated energy. Received two types of mechanical hysteresis loops. The first type was obtained by stretching a terpoly‐ mer sample from 10% to 100% at elongation growing by 10% (Figure 7). The second one was

obtained by stretching at constant elongation of 100% (Figure 8).

**Figure 7.** Mechanical hysteresis loops at elongation growing by 10% of the terpoly(ester-aliphatic-amide).

**Figure 8.** Mechanical hysteresis loops at a constant elongation of 100% of terpoly(ester-aliphatic-amide) and terpoly(es‐ ter-ether-amide), where the ester block was 5GT: εs – elastic elongation, εhs – delayed high-elastic elongation, εps – permanent set, A – area proportional to the dissipated elastic energy, B – area proportional to the dissipated high-elas‐

tic energy, C – area proportional to the accumulated energy.

The crystal structure of PTT homopolymer is observed at scattering angles 2Θ of 15.08°, 16.51°, 19.17°, 23.19°, 24.39°, and 26.91°. The most intense diffraction peaks appear in doublets. The diffraction pattern of PA12 homopolymer has one wide diffraction maximum with two extreme points: 20.44° and 21.26°, which are a result of overlapping of the reflections origi‐ nating from two polymorphic structures γ and α PA12. The terpolymer diffraction patterns exhibit only two reflections with the glancing angles 2Θ corresponding to the angle values on the PA12 diffraction pattern.

**Figure 9.** WAXS diffractograms of PTT, PA12, and multiblock terpolymers where the soft phase is DLA.

The qualitative analysis of the diffactograms (Figures 9 and 10) suggests that in the obtained terpolymers composed of the ester and amide hard blocks, only the amide block is responsible for the formation of the crystalline phase. For all the series, terpolymers where the ester block is trimethylene terephtalate exhibits poor-shaped and very wide diffraction maximum. This may indicate the weakest capacity for crystallization of these polymers. There are fewer polymorphic structures γ of PA12 in terpolymers where the matrix is DLAol than in those where the matrix is PTMO.

**Figure 10.** WAXS diffractograms of PTT, PA12, and multiblock terpolymers where the soft phase is PTMO..

## **3.6. Thermal properties**

The terpolymer samples was heated, cooled, and reheated in the temperature range from -90°C to 250°C. The DSC curves of multiblock elastomers can be divided into two parts. The trend of the first part, which is in the low-temperature range of -90°C < T < 25°C, characterizes the processes caused by the changes in the soft phase. The trend of the second part of these curves, above 25°C, characterizes the thermal properties of the hard phase. The glass transition temperature Tg, change of specific heat ∆Cp, crystallization temperature Tc, enthalpy of crystallization ∆Hc, melting point Tm, and melting enthalpy ∆Hm for the soft and hard phases in both series of terpolymers was determined. The influence of chemical compositions of ester block on the thermal properties and on the values of phase change temperatures of the products are presented in Table 6 and are shown in Figures 11–16.


Tg1, Tm1 – glass transition and melting point temperatures, respectively in low-temperature region; ∆Cp – heat capacity change in Tg1; ∆Hm1 – heat of melting at Tm1; Tm2, Tm3, Tc – melting point temperatures and crystallization temperatures, respectively in high-temperature region, ∆Hc - crystallization heat in Tc; ∆Hm2 – heat of melting at Tm2; ∆Hm3 – heat of melting at Tm3

**Table 6.** The DSC study results for terpolymers.

The qualitative analysis of the diffactograms (Figures 9 and 10) suggests that in the obtained terpolymers composed of the ester and amide hard blocks, only the amide block is responsible for the formation of the crystalline phase. For all the series, terpolymers where the ester block is trimethylene terephtalate exhibits poor-shaped and very wide diffraction maximum. This may indicate the weakest capacity for crystallization of these polymers. There are fewer polymorphic structures γ of PA12 in terpolymers where the matrix is DLAol than in those

**Figure 10.** WAXS diffractograms of PTT, PA12, and multiblock terpolymers where the soft phase is PTMO..

are presented in Table 6 and are shown in Figures 11–16.

The terpolymer samples was heated, cooled, and reheated in the temperature range from -90°C to 250°C. The DSC curves of multiblock elastomers can be divided into two parts. The trend of the first part, which is in the low-temperature range of -90°C < T < 25°C, characterizes the processes caused by the changes in the soft phase. The trend of the second part of these curves, above 25°C, characterizes the thermal properties of the hard phase. The glass transition temperature Tg, change of specific heat ∆Cp, crystallization temperature Tc, enthalpy of crystallization ∆Hc, melting point Tm, and melting enthalpy ∆Hm for the soft and hard phases in both series of terpolymers was determined. The influence of chemical compositions of ester block on the thermal properties and on the values of phase change temperatures of the products

where the matrix is PTMO.

38 Thermoplastic Elastomers - Synthesis and Applications

**3.6. Thermal properties**

**Figure 11.** The first heating scans of the terpolymers of series I.

**Figure 12.** The second heating scans of the terpolymers of series I.

**Figure 13.** The cooling scans of the terpolymers of series I.

Synthesis and Properties of Multiblock Terpoly (Ester-Aliphatic-Amide) and… http://dx.doi.org/10.5772/61215 41

**Figure 14.** The first heating scans of the terpolymers of series II

**Figure 12.** The second heating scans of the terpolymers of series I.

40 Thermoplastic Elastomers - Synthesis and Applications

**Figure 13.** The cooling scans of the terpolymers of series I.

**Figure 15.** The second heating scans of the terpolymers of series II.

**Figure 16.** The cooling scans of the terpolymers of series II.

Characteristic for xGT-PTMO-PA12 terpolymers is the constant value of the glass transition temperature (TgPTMO ≈ -72°C) in the low-temperature region, which is independent of the ester block chemical structure. The glass transition of PTMO homopolymer is -90°C and differs from the obtained terpolymers by 20°C. For the xGT-DLAol-PA12 terpolymers, difference between Tg of flexible block (TgDLAol ≈ 61°C) and terpolymers is even greater and amounts 40°C. The immobilization of the chain-ends of the flexible block by the chemical bond enhances its Tg of about 5°C–10°C, and the interaction of the dispersed phase on this block by a further 5°C. The difference between the homopolymer glass transition temperatures and obtained terpolymers received up to 20°C and 40°C, therefore, cannot be explained by immobilization of the chainends or by interphase interactions. Probably, further increase in Tg1 is responsible for the terpolymers dissolution of the short ester sequence in the soft phase. The poor-shaped melting endotherm is observed in the low-temperature region in terpolymers of series I. It determined the heat of fusion of the soft phase. With the increase of the number of carbons separating the terephthalate groups in the ester block of terpolymers also increased the melting point temperature of the crystalline fraction of PTMO blocks. This shows that the purity of the PTMO soft phase increases. In the high-temperature part of the DSC curves two melting endotherms are observed. The first thermal effect, which is called annealing endotherm, is characteristic for many polymers crystallized from the melt and it disappeared during the second heating. It is understood that it accounts for the melting of defected, small crystallites and is associated with the heat of dispersion of the mesomorfic aggregates occurring in terpolymers. The melting point temperature increased with the increasing amounts of the carbons separating the terephthalate groups in the ester block of terpolymers. For the samples with odd number of carbons x in the ester block, Tm is by 10°C–15 °C lower than in the case of the other terpolymers (principle of parity). The same regularity is observed during cooling of the materials. The difference in the chemical structure of the esters block practically does not influence on the maximal temperature range of application, which is about 200°C.

**Figure 17.** DMTA analysis of the terpolymers of series I.

**Figure 16.** The cooling scans of the terpolymers of series II.

42 Thermoplastic Elastomers - Synthesis and Applications

Characteristic for xGT-PTMO-PA12 terpolymers is the constant value of the glass transition temperature (TgPTMO ≈ -72°C) in the low-temperature region, which is independent of the ester block chemical structure. The glass transition of PTMO homopolymer is -90°C and differs from the obtained terpolymers by 20°C. For the xGT-DLAol-PA12 terpolymers, difference between Tg of flexible block (TgDLAol ≈ 61°C) and terpolymers is even greater and amounts 40°C. The immobilization of the chain-ends of the flexible block by the chemical bond enhances its Tg of about 5°C–10°C, and the interaction of the dispersed phase on this block by a further 5°C. The difference between the homopolymer glass transition temperatures and obtained terpolymers received up to 20°C and 40°C, therefore, cannot be explained by immobilization of the chainends or by interphase interactions. Probably, further increase in Tg1 is responsible for the terpolymers dissolution of the short ester sequence in the soft phase. The poor-shaped melting endotherm is observed in the low-temperature region in terpolymers of series I. It determined the heat of fusion of the soft phase. With the increase of the number of carbons separating the terephthalate groups in the ester block of terpolymers also increased the melting point temperature of the crystalline fraction of PTMO blocks. This shows that the purity of the PTMO soft phase increases. In the high-temperature part of the DSC curves two melting endotherms are observed. The first thermal effect, which is called annealing endotherm, is characteristic for many polymers crystallized from the melt and it disappeared during the second heating. It is understood that it accounts for the melting of defected, small crystallites and is associated with the heat of dispersion of the mesomorfic aggregates occurring in terpolymers. The melting point temperature increased with the increasing amounts of the carbons separating the terephthalate groups in the ester block of terpolymers. For the samples with odd number of

**Figure 18.** DMTA analysis of the terpolymers of series II.

The effect of temperature on the dynamic mechanical properties of TPEEA depending on the chemical structure of ester block was presented in Figures 17 and 18. The obtained temperature spectra are the curves being characteristic for the thermoplastic elastomers. The spectra of the storage modulus have three temperature regions, in which the courses E'=t(T) differ signifi‐ cantly. In the temperature region from 100°C to -70°C (PTMO) or -20°C (DLAol), the obtained TPEEAs exhibited a constant, characteristic for the glass state, the value of storage modulus above 1 GPa. In the region from -70°C (PTMO) or -20°C (DLAol) to 10°C, a decrease of modulus was observed that was caused by the appearance of viscoelasticity relaxation processes. A further increase of temperature caused the occurrence of a wide "plateau" of elastic state, which at a temperature of 120°C terminates by a rapid lowering at the point of crystallite melting of the hard block phase. For all xGT-PTMO-PA12 samples, the tgδ curves possess a broad relaxation peak composed of two relaxation transitions α and α'. They may be linked with the glass transition temperatures for region composed of pure PTMO and mixture of PTMO/xGT of the amorphous phase and interphase. Maximum α'' is a result of the relaxation effect of the amorphous phase of PA12. xGT-DLAol-PA12 terpolymers has one narrow and high damping peak. Probably, in these terpolymers the interphase is smaller because of weak mixing of ester blocks with DLAol matrix.

## **4. Conclusion**

The synthesis, structure, and properties of poly[(multi-methylene terephthalate)-block- (oxytetramethylene)-block-(laurolactam)] and poly[(multi-methylene terephthalate)-block- (linoleic alcohol dimer)-block-(laurolactam)] terpolymers have been reviewed in this chapter. The influence of the number of carbons separating the terephtalate groups of the ester groups in the benzene ring of other blocks and on the properties and structure of these elastomers have been evaluated.

A series of new thermoplastic block elastomers was prepared by melt polycondensation. Synthesis of poly(ester-b-ether-b-amide) terpolymers was a two-step process in the presence of a titanate catalyst. The first step was the transesterification reaction of dimethyl terephtha‐ late and glycol and the esterification reaction of α,ω-dicarboxylic oligo(laurolactam) with oligo(oxytetramethylene)diol or linoleic alcohol dimer, which is taking place simultaneously in another reactor. The second step was polycondensation reaction of two previously pre‐ pared intermediate compounds. A detailed description of this synthesis is given in previous papers [36, 37].

13C NMR and FT-IR methods were used to confirm terpolymers assumed chemical structure. Obtained copolymers had all characteristic FT-IR bands for esters, aliphates or ether, and amides. There is no in obtained terpolymers a strong, wide band for the O-H stretch in the region 3300-3000 cm-1, which is observed in FT-IR spectra of pure dicarboxylic oligoamides. It proves that these blocks are built into the copolymer macromolecule. This conclusion is confirmed by the peak presence at 39.56 ppm in 13C NMR spectra.

The degree of phase separation of soft phase and the degree of crystallinity of hard phase was determined by DSC analysis. The interphase size was also estimated, and the occurrence of the semicrystalline structures was noticed. The DMTA and WAXS methods supplemented these data. It was found that synthesized copolymers exhibit a multiphase (crystallineamorphous) physical structure. The amorphous phases (matrix) are composed of the flexible blocks PTMO or DLAol that are contaminated by short ester sequences. The crystalline phase (domains) is composed of the hard blocks PA12 and is disordered by admixtures of the xGT blocks. The number of carbons separating the terephthalate groups in the ester block has little effect on the physical properties of the terpolymers obtained by slightly increasing the amorphous phase.

It has been concluded that in both series the best elastic residues have the terpolymer with the number of carbons x=5. Probably the interphase of these samples is large and well shaped. Better elastic properties are exhibited by terpolymers of series I, where the soft phase is PTMO because these block is more flexible (large capability for motion and rotation of ether bond).

Obtained terpolymers exhibit unique properties, such as low glass transition temperature, a wide temperature range of application, fast cristallization, good mechanical properties, including good elasticity, thermal stability, and thermal and chemical resistance, and may find application in practice.

## **Author details**

The effect of temperature on the dynamic mechanical properties of TPEEA depending on the chemical structure of ester block was presented in Figures 17 and 18. The obtained temperature spectra are the curves being characteristic for the thermoplastic elastomers. The spectra of the storage modulus have three temperature regions, in which the courses E'=t(T) differ signifi‐ cantly. In the temperature region from 100°C to -70°C (PTMO) or -20°C (DLAol), the obtained TPEEAs exhibited a constant, characteristic for the glass state, the value of storage modulus above 1 GPa. In the region from -70°C (PTMO) or -20°C (DLAol) to 10°C, a decrease of modulus was observed that was caused by the appearance of viscoelasticity relaxation processes. A further increase of temperature caused the occurrence of a wide "plateau" of elastic state, which at a temperature of 120°C terminates by a rapid lowering at the point of crystallite melting of the hard block phase. For all xGT-PTMO-PA12 samples, the tgδ curves possess a broad relaxation peak composed of two relaxation transitions α and α'. They may be linked with the glass transition temperatures for region composed of pure PTMO and mixture of PTMO/xGT of the amorphous phase and interphase. Maximum α'' is a result of the relaxation effect of the amorphous phase of PA12. xGT-DLAol-PA12 terpolymers has one narrow and high damping peak. Probably, in these terpolymers the interphase is smaller because of weak

The synthesis, structure, and properties of poly[(multi-methylene terephthalate)-block- (oxytetramethylene)-block-(laurolactam)] and poly[(multi-methylene terephthalate)-block- (linoleic alcohol dimer)-block-(laurolactam)] terpolymers have been reviewed in this chapter. The influence of the number of carbons separating the terephtalate groups of the ester groups in the benzene ring of other blocks and on the properties and structure of these elastomers

A series of new thermoplastic block elastomers was prepared by melt polycondensation. Synthesis of poly(ester-b-ether-b-amide) terpolymers was a two-step process in the presence of a titanate catalyst. The first step was the transesterification reaction of dimethyl terephtha‐ late and glycol and the esterification reaction of α,ω-dicarboxylic oligo(laurolactam) with oligo(oxytetramethylene)diol or linoleic alcohol dimer, which is taking place simultaneously in another reactor. The second step was polycondensation reaction of two previously pre‐ pared intermediate compounds. A detailed description of this synthesis is given in previous

13C NMR and FT-IR methods were used to confirm terpolymers assumed chemical structure. Obtained copolymers had all characteristic FT-IR bands for esters, aliphates or ether, and amides. There is no in obtained terpolymers a strong, wide band for the O-H stretch in the region 3300-3000 cm-1, which is observed in FT-IR spectra of pure dicarboxylic oligoamides. It proves that these blocks are built into the copolymer macromolecule. This conclusion is

The degree of phase separation of soft phase and the degree of crystallinity of hard phase was determined by DSC analysis. The interphase size was also estimated, and the occurrence of

confirmed by the peak presence at 39.56 ppm in 13C NMR spectra.

mixing of ester blocks with DLAol matrix.

44 Thermoplastic Elastomers - Synthesis and Applications

**4. Conclusion**

have been evaluated.

papers [36, 37].

Joanna Rokicka\* and Ryszard Ukielski

\*Address all correspondence to: joanna.rokicka@zut.edu.pl

West Pomeranian University of Technology Szczecin, Poland

## **References**


[6] Holden G. Understanding thermoplastic elastomers. Munich: Hanser Publishers;

[7] Bhowmick A.K., editor. Current topics in Elastomer research. Boca Raton: CRC Press;

[8] Dick J.S., editor. Rubber Technology. Compounding and Testing for Performance.

[9] Lal J., Mark J.E., editors. Advances in elastomer and rubber elasticity, proceedings

[12] Miller J.A., Shaow B.L., Hwang K.K.S., Wu K.S., Gibson P.E., Cooper S.L. Macromo‐

[13] White J.R., De S.K., editors. Rubber Technologist's Handbook. Shawbury: Rappra

[14] Rzymski W.M., Radusch H.J. Nowe elastomery termoplastyczne. Polimery. 2005;4.

[17] Mark H., Flory P.J., editors. High Polymers. New York: John Wiley & Sons; 1964.

[15] Mark J.E., Erman B., Eirich F.R., editors. Science and technology of rubber. San Die‐

[11] Ng H.N., Allegrazza A.E., Seymour R.W., Cooper S.L. Polymer. 1973;15.

2000.

2008.

Munich: Hanser Publishers; 2001.

46 Thermoplastic Elastomers - Synthesis and Applications

[10] Harrell L.L. Macromolecules. 1969;2(6).

lecule. 1985;18(1).

Technol. Ltd; 2001.

go: Academic Press; 1978.

[19] Yang I.K., Tsai P.H.. Polymer. 2006;47.

of Polymer Science: Part B. 2010;48.

Part A. 2003;41.

[26] Ukielski R. Polimery. 1997;42.

[16] Bayer O. Mod. Plast. 1947;24.

symposium. New York: Plenum Press; 1985.

[18] Van der Schuur M.J., Gaymans R.J. Polymer. 2007;48.

[20] Huang J.J., Keeskkula H., Paul D.R. Polymer. 2006;47.

[27] Ukielski R., Rokicka J. Przemysł Chemiczny. 2010;12.

[21] Krijgsman J., Husken D., Gaymans R.J. Polymer. 2003;44.

[22] Armstrong S., Freeman B., Hiltner A., Baer E. Polymer. 2012;53.

[23] Nery L., Lefebvre H., Fradet A. Journal of Polymer Science: Part A. 2005;43.

[24] Mateva R., Zhilkova K.R., Zamfirova G., Diaz-Calleja R., Garcia-Bernabe A. Journal

[25] Sugi R., Hitaka Y., Sekino A., Yokoyama A., Yokozawa T. Journal of Polymer Science:

