**3.2.2 Modification of condensation thermoplastics by CFPS**

#### **3.2.2.1 Polyesters**

Enzymatic polymerization is an environmentally friendly approach to polymer synthesis and in the contrast to traditional chemical methods it does not need harsh reaction conditions and metallic catalysts. Lipase-catalyzed synthesis of aromatic silicone polyesters (SAPEs) and polyamides (SAPAs) have been reported (Poojari & Clarson, 2010). The SAPEs were synthesized using α,ω-dihydroxyalkyl-terminated PDMS, and the SAPAs were prepared with α,ω-diaminoalkyl-terminated PDMS via transesterification reaction with dimethyl terephthalate in toluene at a temperature in the range 80–90 C. Both types of polymer were liquids at room temperature. Polysiloxane-polyester copolymers were synthesized by polycondensation of a series of diacids and α,ω-bis(3-hydroxypropyl)-PDMS with Novozyme-435. The use of lipase as the catalyst led to carry out the polycondensation reaction under mild conditions (Guo et al., 2008).

A series of novel thermoplastic elastomers, poly(ester-siloxane)s, have been synthesized (Antic et al., 2010). These materials were based on poly(butylenes terephthalate) (PBT) as the hard segments and PDMS-containing prepolymers as the soft segments. In order to increase the compatibility of PDMS copolymers of siloxanes with terminal aliphatic polyester such a triblock copolymer polycaprolactone-*block*-polydimethylsiloxane-*block*-polycaprolactone (PCL-*b*-PDMS-*b*-PCL) was used. The thermal stability of the poly(ester-siloxane)s was higher than that of PBT homopolymer, and the reduced crystallinity of the hard segments have been observed.

Thermoresponsive shape memory polymers (SMPs) are a class of materials that change shape upon exposure to heat. They are lightweight, easy to fabricate and may be biodegradable. Poly(-caprolactone) (PCL)-based SMPs have received much attention due to the biocompatibility, biodegrability, and elasticity of PCL. PCL is useful as a crystalline switching segment for SMPs as its Ttrans is a well-defined Tm in the range of 45-60 C with increasing Mn. Such Ttrans values are useful for *in vivo* deployment as well as other applications which require low heating. To modify properties of PCL-based SMPs, AB polymer networks have been prepared through incorporation of organic hard or soft segments. PDMS with extremely low Tg (-123 C) is a particularly effective soft segment candidate. Schoener et al. (2010) prepared organic-inorganic SMPs comprised of inorganic PDMS segments, terminated by aminopropyl groups, and organic PCL segments. The resulting SMP network exhibited excellent shape fixity and recovery. By changing the PDMS length, the thermal, mechanical, and surface properties were systematically alternated.

Carbon nanotubes (CNTs) are the ideal reinforcing agents for high-strength polymer composites because of their tremendous mechanical strength, their Young's modulus is ca. 1000 GPa and it is much higher than that of the conventional carbon fibres (200-800 GPa). For good reinforcement effect the surface of CNTs must be strongly bonded to the polymer matrix. Sidewall functionalization of CNTs, introduction mainly carboxylic groups, makes possible to chemically attach these nanofillers with polymers. Chen and Shimizu (2008) prepared the nanocomposites of poly(L-lactide) (PLLA) reinforced by aminopropylisooctyl POSS modified multi-wall nanotubes (MWNTs) (MWNT-*g*-POSS). They have observed the homogeneous dispersion of MWNTs throughout the PLLA MWNT-*g*-POSS composites without any aggregation. The fractial surface of the composites showed not only a uniform dispersion of MWNTs but also a strong interfacial adhesion with the matrix.

#### **3.2.2.2 Polyamides**

168 Thermoplastic Elastomers

isocyanurate derivatives of hexamethylene diisocyanates R(NCO)x, 3,3,4,4,5,5,6,6,7,7,8,8,8 tridecafluoro-1-octanol, ethylene glycol dimethacrylate (EGDMA), dicyclohexyl acrylate, and dipercarbonate (DCPD), towards dibutyltin dilaurate (DBTDL). A transparency of the obtained materials gave an evidence that no phase separation took place. The fluorinated

Polymerization of fumarate monomers provide polymers with a substituent in every methylene unit. These polymers are applied as high performance materials, as biodegradable polymers, low dielectric materials, oxygen permeability membranes, liquid crystal, contact lens (CL) materials, etc. Among them, CL is known well as the lens equipped on a cornea foe vision correction, and the CL materials are required both for the oxygen permeable property for breathing of corneal cell and the hydrophilic property for not repelling a tear and to protect a lipid deposition. Polymerizations of amphiphilic fumarate (containing hydrophilic and hydrophobic substituents) monomers give polymers with high oxygen permeability, hydrophilicity and transparency required for CL materials. Novel dissymmetric fumarate monomers having both alkoxyethyl group [2-(2-methoxyethoxy) ethyl, 2-(2-(2-methoxy-ethoxy)ethoxy)ethyl] and a bulky 3-[tris(trimethylsiloxy)silyl]propyl group were radically polymerized with styrene and N-vinylpyrrolidone (NVP). Various membranes, prepared by copolymerization of fumarate monomers with NVP or NVP and HEMA, showed much better transparency, as compared to the membranes containing 3-

Enzymatic polymerization is an environmentally friendly approach to polymer synthesis and in the contrast to traditional chemical methods it does not need harsh reaction conditions and metallic catalysts. Lipase-catalyzed synthesis of aromatic silicone polyesters (SAPEs) and polyamides (SAPAs) have been reported (Poojari & Clarson, 2010). The SAPEs were synthesized using α,ω-dihydroxyalkyl-terminated PDMS, and the SAPAs were prepared with α,ω-diaminoalkyl-terminated PDMS via transesterification reaction with dimethyl terephthalate in toluene at a temperature in the range 80–90 C. Both types of polymer were liquids at room temperature. Polysiloxane-polyester copolymers were synthesized by polycondensation of a series of diacids and α,ω-bis(3-hydroxypropyl)-PDMS with Novozyme-435. The use of lipase as the catalyst led to carry out the polycondensation

A series of novel thermoplastic elastomers, poly(ester-siloxane)s, have been synthesized (Antic et al., 2010). These materials were based on poly(butylenes terephthalate) (PBT) as the hard segments and PDMS-containing prepolymers as the soft segments. In order to increase the compatibility of PDMS copolymers of siloxanes with terminal aliphatic polyester such a triblock copolymer polycaprolactone-*block*-polydimethylsiloxane-*block*-polycaprolactone (PCL-*b*-PDMS-*b*-PCL) was used. The thermal stability of the poly(ester-siloxane)s was higher than that of PBT homopolymer, and the reduced crystallinity of the hard segments

polymers exhibit good hydro- and oleofobicity (Darras et al., 2007).

[tris-(trimethylsilyloxy)silyl]propyl methacrylate (Ohnishi et al. 2009).

**3.2.2 Modification of condensation thermoplastics by CFPS** 

reaction under mild conditions (Guo et al., 2008).

**3.2.2.1 Polyesters** 

have been observed.

**3.2.1.5 Radical polymerization of dissymmetric fumarates** 

Alongi et al. (2009) have reported the preparation of inorganic-organic hybrids made of POSS and polyamide 6 (PA 6) produced by melt mixing of the two components or by the *in situ* polymerization of -caprolactam in the presence of POSS. The last method did not result in any POSS self-aggregation in the polymer matrix, achieving a very fine cubic dispersion of nanometric dimensions. The nearly nano-sized aromatic polyamide particles with amino groups, known as poly(amino-amide) PAMAM, were prepared by Yoshioka (2009). They were modified with silane coupling agent, i.e. 3-glycidoxypropyltriethoxysilane (GPTES), and further complexed with ZnO particles. The finally ZnO-based materials have specific optical properties: they show excellent optical absorption properties in UV region and high transmittance in the visible region.

#### **3.2.2.3 Polyimides**

Polyimides (PIs) are well-known engineering plastics with excellent thermal, mechanical, dielectric, and optical properties. They also have good chemical resistance and high dimensional stability. However the main deficiency of aromatic polyimides is their insolubility in organic solvents and infusibility or extremely high glass transition temperature (Tg) which makes their processing very difficult. One approach to increase the solubility and processability of polyimides is the introduction of flexible linkages or bulky units into the polymer chain. The incorporation of PDMS sequences in PIs has afforded new copolymers with good processability, low water absorption, atomic oxygen resistance, and excellent

Modification of Thermoplastics with Reactive Silanes and Siloxanes 171

failure was observed with increasing PDMDPS content. At temperature of –30 C the impact strength increased from 8 kgfcm/cm to 52 kgfcm/cm for neat PC and PC/PDMDPS blends

An interesting group of thermoplastic elastomers (TPE), characterized by a great stiffness at low temperature, are block copolymers prepared from polycarbonates (PC) and PDMS (PC/PDMS). Copolymers PC/PDMS are usually prepared in reaction of phosgene with bisphenol A in the presence of PDMS containing terminal bisphenol groups (van Aert et al., 2001). Block PC/PDMS copolymers find applications in a manufacture of membranes,

Multi-walled carbon nanotubes/polycarbonate nanocomposites (MWNT/PC) have been prepared (Wang et al., 2010). Functionalized MWNTs-COOH with α,ω-3-aminopropyl-PDMS, were used to produce MWNT/PC nanocomposites. The results showed that siloxane–modified carbon nanotubes were dispersed well in the PC matrix, and the tensile strength, flexural strength, flexural modulus, and flame retardancy of MWNT/PC composites were better than these of MWNT-COOH/PC. Siloxane-modified MWNTs can

Thermoplastic polyurethanes (TPUs) are obtained by a polyaddition reaction of diisocyanates to long, hydroxyl-terminated oligomers (polyols) and short diols, which are often named as chain extenders. The polyurethanes are multi-block copolymers consisting of hard segments (HS) and soft segments (SS). The thermodynamic incompatibility between alternating segments usually induces a two-phase structure with soft domains containing mostly the polyol moieties, and hard domains made up of diisocyanate-chain extender sequences. If incompatibility exists between the two block components, a microphase separation will occur and the hard domains will provide a reinforcement to the system. The type of diisocyanate has a marked effect on a strength of a final material. The most often applied isocyanates are: 4,4'-methylenediphenyl diisocyanate (MDI), tolylene diisocyanate (TDI), bis(4-isocyanatocyclohexyl) methane (HMDI), isophorone diisocyanate (IPDI). TPUs are widely used for high-performance applications, as: medical implants (Arkles, 1983), membranes, adhesives and coatings, especially when a high tear and a tensile strength or good wear and abrasion resistance are required. Another special features of TPUs are their low-temperature elasticity, a smoothness for the touch, an electrical insulation and a good

Over the past three decades, considerable attention has been directed to utilization of the PDMS as a soft segment component in polyurethanes and polyurethaneureas. Polysiloxane SS are introduced by PDMS-diols or hydroxyalkenyl or aminopropyl or ethyl-piperazine terminated PDMS. However, the tensile strength and elongation at break of these materials compared to those based on polyether (PET) or polyester (PES) SS are visibly poorer. Thus, various co-SS components, mainly based on poly(alkenyl oxide) have been utilized. Sheth et al. (2005) selected poly(propylene oxide) (PPO) as a second SS component, because his solubility parameter (23.5 J1/2/cm3/2) is in between that of PDMS (15.6 J1/2/cm3/2) and urea (45.6 J1/2/cm3/2). The inter-segmental mixing between PPO and urea segments could modify

the nature of interphase between the soft matrix and the hard urea microdomains.

which are used for selective separation of gases (LeGrand, 1972).

**3.2.3 Modification of polyurethanes and polyureas by CFPS** 

improve the electrical properties of the nanocomposites at low loading in PC.

respectively.

chemical resistance.

adhesion. The unique properties of the imide-siloxane copolymeric materials (PSIs) make them especially attractive for applications in microelectronics and as structural adhesives.

A series of amorphous poly(imide siloxane)s (PIS) with different PDMS contents and segmental lengths were synthesized via condensation reaction by Ku & Lee (2007). A variety of morphologies of PIS films, including unilamellar vesicle, multilamellar vesicle, sea-island and others, were found as the function of the content and the segmental length of PDMS, as well as the coexistence of large-scale phase separations and nano-scale phase separation of approximately 20 nm.

Lu et al. (2006) prepared, using sol-gel method, polyimide/polydiphenylsiloxane (PI/PDPS) composite films with high thermal stability near pure PI. Polysiloxanes well dispersed in polyimide matrix, without macroscopic separation for the composite films was observed with low content of DPS, while large domain of polysiloxane was formed in films with high DPS content. The introduction of DPS into PI improved the elongation at break but the composite films still remained with higher modulus and tensile strength.

Aromatic polyimides (PIs) have been of great interest in gas separation membranes because of their gas selectivity and excellent thermal and mechanical properties. Recently, novel triaminebased hyperbranched PIs are applied for high-performance gas-separation materials. Hybridization of PIs with inorganic compounds has been focused also to improve the gas transport properties. Hyperbranched PIs prepared by polycondensation of a triamine 1,3,5 tris-(4-aminophenoxy)benzene and 4,4'-(heksafluoroisopropylidene) diphthalic dianhydryde (6FDA) were modified by sol-gel reaction using tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS), and 3-aminopropyltrimethoxysilane (Suzuki et al., 2008).

New copolymers, polysiloxane-imides (PSIs), have been prepared from α,ω-(bisaminopropyl)dimethylsiloxane oligomers (ODMS) and aromatic dianhydrides: 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), and 6FDA, (Krea et al., 2004). Membranes of these new PSIs have been used to remove polar organics from water by pervaporation.

Bismaleimide (BMI) has the unique combination of a high service temperature, good toughness and epoxy-like processing. Composites of BMI with surface-modified SiO2 nanoparticles by amino-functionalized silane coupling agent has been studied (Yan et al., 2008). The nanocomposites with surface-modified SiO2 showed better wear resistance and lower frictional coefficient than that with unmodified fillers.
