**3. Results and discussion**

#### **3.1. Preparation of chain extender**

The preparation of 2,5-bis(4-hydroxyphenyl)thiazolo-[5,4d] thiazole and 2,5-bis(4-hydroxy-3-methoxyphenyl) thiazolo [5,4d] thiazole were conducted according to the reaction shown in Scheme 1. The starting reagent involved for the synthesis of both the compounds were rubeanic acid and either 4-hydroxybenzaldehyde or vanillin with the presence of phenol. Subsequently, both chain extenders prepared were being used in the preparation of LCPUE. Identification of the chemical structures of the aforementioned products was monitored primarily with FT-IR spectroscopy and further confirmation was carried out by 1H-NMR spectrophotometer.

**Scheme 1.** Preparation of Compound I and II

#### **3.2. Polymer synthesis**

22 Polyurethane

performed at room temperature.

**3. Results and discussion** 

spectrophotometer.

**3.1. Preparation of chain extender** 

**Scheme 1.** Preparation of Compound I and II

observe the behavior of polymers such as glass transition point (Tg), melting point (Tm) and isotropic temperature (Ti). It was conducted utilizing Perkin Elmer Pyris Series 7 thermal analyzer under Nitrogen flux at 100C/min rate of heating. Textures of mesomorphic phases were displayed by Nikon Eclipse E600 polarized microscope equipped with MS600 Linkam Hot stage and SONY CCD-IRIS Color Video Camera. The heating rate was 5oC/min and 10oC/min for the cooling rate. Sample was placed between two thin round glasses and it was then transferred onto microscope fitted with the hot stage to be analyzed. Siemens X-ray Diffractometer model D5000 equipped with a CuKα target at 40KV and 40mA was used in obtaining X-ray scattering curve. Tensile strain properties of LCPUE films were measured by Instron Testing instrument at a constant speed of 500mm/min (speed) where the measurements were performed at room temperature. Brookfield viscometer was used to measure the fluid viscosity where suitable spindle and speed were chosen and it was also

The preparation of 2,5-bis(4-hydroxyphenyl)thiazolo-[5,4d] thiazole and 2,5-bis(4-hydroxy-3-methoxyphenyl) thiazolo [5,4d] thiazole were conducted according to the reaction shown in Scheme 1. The starting reagent involved for the synthesis of both the compounds were rubeanic acid and either 4-hydroxybenzaldehyde or vanillin with the presence of phenol. Subsequently, both chain extenders prepared were being used in the preparation of LCPUE. Identification of the chemical structures of the aforementioned products was monitored primarily with FT-IR spectroscopy and further confirmation was carried out by 1H-NMR LCPUE based on thiazolo [5,4d] thiazoles moiety were synthesized from long chain of diol (PEG 3000, 2000 and 1000) with an excess of diisocyanate (MDI) via addition reaction to give the terminal reactive group which results in the formation of 'extended diisocyanate' or isocyanate pre-polymer. Then, 2,5-bis(4-hydroxyphenyl) thiazolo-[5,4d] thiazole [I] and 2,5 bis(4-hydroxy-3- methoxyphenyl) thiazolo [5,4d] thiazole [II] were added acting as a chain extender in order to convert the pre-polymer into long chain LCPUE. The general route for the preparation of LCPUE was outlined in Scheme 2, yield and viscosity of LCPUE were listed in Table 1 and the data showed that the range of the viscosities and yields obtained were 10,744 to 40 692 cP and 76-87 %, respectively. Range of the viscosities obtained also provides the information of the molecular weight of each polymer synthesized where high value of viscosity indicates high molecular weight of the polymer produced and vice versa (Bagheri & Pourmoazzen, 2008). In this case, all LCPUE samples displayed fairly high molecular weight in accordance with the results demonstrated.

**Scheme 2.** General route for the preparation of LCPUE VI (a-c) and VII (a-c)

#### **3.3. Structural elucidation**

FT-IR was employed to verify functional groups of the pre-polymer, compound I and II, and LCPUE. Prior to the formation of LCPUE which is referring to the pre-polymer state, in the region of 2270 cm-1 a peak was observed which was assigned to –N=C=O- (diisocyanate) whereas according to the IR spectra of compound I and II, a peak was found at 3492 cm-1 and 3334 cm-1 which corresponds to –OH functional group in the chemical structure. The disappearance of both the bands of -N=C=O- in pre-polymer and – OH of compound I and II, indicates the completion of the reaction of preparation of LCPUE and this fact was also supported with the appearance of new absorption bands at 3356.84cm-1 ( N-H- stretching ) and 1782.5cm-1 (carbonyl group) which were attributed to the urethane linkage, –NHCOO- (Zhang et al., 2008; Issam, 2007). Furthermore, the peak at 2884.89 cm-1 was ascribed to –CH stretching, whereas the band representing C=C aromatic can be found at 1598.59 cm-1. Figure 1 displayed the FTI-R spectrum of LCPUE VIIa and based on the results obtained, the characteristic absorption bands of FT-IR spectra for the other LCPUE were almost identical to one another. The fact that differentiates LCPUE VI and LCPUE VII was the presence of the methoxy group and it was proven in the FTIR spectrum of LCPUE VIIa, where a peak displayed at the region of 1024.27 cm-1 corresponded to the methoxy group.

New Liquid Crystalline Polyurethane Elastomers

Containing Thiazolo [5,4d] Thiazole Moiety: Synthesis and Properties 25

**Figure 2.** 1H-NMR spectrum of LCPUE VIIa

**Figure 3.** 13 C-NMR spectra of LCPUE VIIa

Other than FT-IR and 1H-NMR analysis, 13C-NMR was performed in order to clarify the structure of LCPUE prepared. 13C-NMR spectra portrayed in Figure.3 which represents LCPUE VIIa shows that the formation of urethane linkage (NHCOO) was determined by the

Further confirmation of chemical composition of LCPUE produced was carried out by means of Nuclear Magnetic Resonance spectroscopy (NMR). 1H-NMR spectrum of LCPUE VIIa was illustrated in Figure.2. A singlet peak centered at 8.76 ppm was assigned to – NHCOO- and this proved the formation of urethane linkage. The appearance of multiplet peaks at 7.53-6.99 ppm and singlet peak at 3.87 ppm was attributed to the aromatic protons and the protons in methoxy group, respectively. Aliphatic chain of polyol (PEG 1000) was detected in the region of 1.23-1.64 ppm.

**Figure 1.** FTIR spectrum of LCPUE VIIa

New Liquid Crystalline Polyurethane Elastomers

Containing Thiazolo [5,4d] Thiazole Moiety: Synthesis and Properties 25

**Figure 3.** 13 C-NMR spectra of LCPUE VIIa

(diisocyanate) whereas according to the IR spectra of compound I and II, a peak was found at 3492 cm-1 and 3334 cm-1 which corresponds to –OH functional group in the chemical structure. The disappearance of both the bands of -N=C=O- in pre-polymer and – OH of compound I and II, indicates the completion of the reaction of preparation of LCPUE and this fact was also supported with the appearance of new absorption bands at 3356.84cm-1 ( N-H- stretching ) and 1782.5cm-1 (carbonyl group) which were attributed to the urethane linkage, –NHCOO- (Zhang et al., 2008; Issam, 2007). Furthermore, the peak at 2884.89 cm-1 was ascribed to –CH stretching, whereas the band representing C=C aromatic can be found at 1598.59 cm-1. Figure 1 displayed the FTI-R spectrum of LCPUE VIIa and based on the results obtained, the characteristic absorption bands of FT-IR spectra for the other LCPUE were almost identical to one another. The fact that differentiates LCPUE VI and LCPUE VII was the presence of the methoxy group and it was proven in the FTIR spectrum of LCPUE VIIa, where a peak displayed at the region of

Further confirmation of chemical composition of LCPUE produced was carried out by means of Nuclear Magnetic Resonance spectroscopy (NMR). 1H-NMR spectrum of LCPUE VIIa was illustrated in Figure.2. A singlet peak centered at 8.76 ppm was assigned to – NHCOO- and this proved the formation of urethane linkage. The appearance of multiplet peaks at 7.53-6.99 ppm and singlet peak at 3.87 ppm was attributed to the aromatic protons and the protons in methoxy group, respectively. Aliphatic chain of polyol (PEG 1000) was

1024.27 cm-1 corresponded to the methoxy group.

detected in the region of 1.23-1.64 ppm.

**Figure 1.** FTIR spectrum of LCPUE VIIa

Other than FT-IR and 1H-NMR analysis, 13C-NMR was performed in order to clarify the structure of LCPUE prepared. 13C-NMR spectra portrayed in Figure.3 which represents LCPUE VIIa shows that the formation of urethane linkage (NHCOO) was determined by the

appearance of the peak at 173.4 ppm. The methylene group presence in the soft segment of PEG can be seen as a sharp and intense peak at 25-29 ppm. More peaks can be observed at 117.8 to 158.7 ppm and 56.2 ppm where they were assigned to the aromatic carbons and the carbon in methoxy group respectively. Significant peaks in all characterization analysis (FT-IR, 1H-NMR and 13C-NMR) were consistent and adequately provide the evidences to support the fact that the reaction of all materials took place and LCPUE was successfully prepared.

New Liquid Crystalline Polyurethane Elastomers

DSC POM

Tg Tm Ti Tm Ti

(oC) (oC) (oC) (oC) (oC)

Containing Thiazolo [5,4d] Thiazole Moiety: Synthesis and Properties 27

further heated after the crystal-nematic transition temperature, and resulted in the disappearing of the texture when reaching the isotropization stage. There were no traces of mesophase transition during the cooling process from POM indicating all samples possessed thermotropic type of liquid crystal. Phase transition temperatures observed through POM were found to be consistent with the corresponding DSC thermograms.

**Figure 4.** DSC traces of (a) LCPUE VIa (b) LCPUE VIIa

WEIGHT

Yield (%)

LCPUE VIa 1000 85 11 108 25.1 176 205 181 200

LCPUE VIb 2000 83 26 456 22.5 153 174 162 180 LCPUE VIc 3000 77 40 692 19.1 139 156 133 161

LCPUE VIIa 1000 76 10 744 15.2 164 187 170 193 LCPUE VIIb 2000 80 22 453 11.8 143 163 148 170

LCPUE VIIc 3000 87 39 981 10.4 125 142 129 149

**Table 1.** Thermal properties of LCPUE VI (a-c) and LCPUE VII (a-c) by DSC and POM

Viscosity cP

SAMPLE PEG MOLECULAR

#### **3.4. Thermal and liquid crystalline behavior of polymers**

The DSC analysis was conducted at a heating rate of 10oC to understand phase separation behavior of all synthesized LPCUE where the transition occurs, observed under polarizing optical microscope (POM) equipped with heating stage and the results obtained from both measurements were listed in Table 1. Based on the DSC thermograms, upon heating, one step transition and two endothermic peaks were detected where each of them indicates glass transition (Tg), melting endotherm, (Tm) and isotropic endotherm (Ti) respectively, which is also the evidence of the existence of mesophase. LCPUE derived from 2,5-bis(4-hydroxy-3 methoxyphenyl) thiazolo [5,4d] thiazole have transition temperatures lower than those derived from 2,5-bis(4-hydroxyphenyl)thiazolo-[5,4d]thiazole. Methoxy group, which acts as a substituent attached to the phenyl ring has the capability to lower the melting and isotropization temperature and caused thermal suppression of the molecule to occur (Al-Dujaili et.al., 2001). The fact was supported by the results illustrated in Fig.4 where it depicts the DSC thermograms of LCPUE. LCPUE VIIa displayed melting point (Tm) at 164oC and isotropization temperature (Ti) at 187oC whereas for LCPUE VIa, Tm was detected at 176oC and Ti at 205oC. The substituent could also act to reduce the coplanarity of adjacent mesogenic groups and increase the diameter or decrease the axial ratio of the mesogens [Li and Chang, 1991]. Due to the higher range between Tm and Ti of LCPUE VIa, the thermal properties of this polymer are higher and more stable compared to LCPUE VIIa. The types of diisocyanates also contribute to the thermal behavior of LCPUE, where MDI based PU was known for having better order of the rigid chain that approaches the decomposition temperature, giving high melting point to the polymer produced (Jieh & Chou, 1996). As for glass transition, it involves mobility of the chain segments and the Tg will be affected by the mobility restriction on the chain segments, (Suresh et.al., 2008) it therefore explains the varying pattern of the Tg values displayed in Table 1. The decreasing values of Tg can be observed as the length of soft segments increases, indicating that the long chain of polyol gave great flexibility characteristics towards the polymer chains where less mobility restrictions occurred and hence resulting in the lower Tg values.

POM was utilized to investigate the type of mesophase by displaying the phase transition that occurred, subsequently providing the polarizing optical microphotographs of the target compounds. The morphology observed on heating and transition temperatures obtained were given in Figures 5 and 6 and the results were summarized in Table 1. It was revealed that all LCPUE showed mesophases upon melting temperature where the thread texture of the nematic phases can be seen. From the photographs taken by POM, the crystal to mesophase transition occurred at temperature ranging from 129 to 181oC. The samples were further heated after the crystal-nematic transition temperature, and resulted in the disappearing of the texture when reaching the isotropization stage. There were no traces of mesophase transition during the cooling process from POM indicating all samples possessed thermotropic type of liquid crystal. Phase transition temperatures observed through POM were found to be consistent with the corresponding DSC thermograms.

**Figure 4.** DSC traces of (a) LCPUE VIa (b) LCPUE VIIa

26 Polyurethane

appearance of the peak at 173.4 ppm. The methylene group presence in the soft segment of PEG can be seen as a sharp and intense peak at 25-29 ppm. More peaks can be observed at 117.8 to 158.7 ppm and 56.2 ppm where they were assigned to the aromatic carbons and the carbon in methoxy group respectively. Significant peaks in all characterization analysis (FT-IR, 1H-NMR and 13C-NMR) were consistent and adequately provide the evidences to support the

The DSC analysis was conducted at a heating rate of 10oC to understand phase separation behavior of all synthesized LPCUE where the transition occurs, observed under polarizing optical microscope (POM) equipped with heating stage and the results obtained from both measurements were listed in Table 1. Based on the DSC thermograms, upon heating, one step transition and two endothermic peaks were detected where each of them indicates glass transition (Tg), melting endotherm, (Tm) and isotropic endotherm (Ti) respectively, which is also the evidence of the existence of mesophase. LCPUE derived from 2,5-bis(4-hydroxy-3 methoxyphenyl) thiazolo [5,4d] thiazole have transition temperatures lower than those derived from 2,5-bis(4-hydroxyphenyl)thiazolo-[5,4d]thiazole. Methoxy group, which acts as a substituent attached to the phenyl ring has the capability to lower the melting and isotropization temperature and caused thermal suppression of the molecule to occur (Al-Dujaili et.al., 2001). The fact was supported by the results illustrated in Fig.4 where it depicts the DSC thermograms of LCPUE. LCPUE VIIa displayed melting point (Tm) at 164oC and isotropization temperature (Ti) at 187oC whereas for LCPUE VIa, Tm was detected at 176oC and Ti at 205oC. The substituent could also act to reduce the coplanarity of adjacent mesogenic groups and increase the diameter or decrease the axial ratio of the mesogens [Li and Chang, 1991]. Due to the higher range between Tm and Ti of LCPUE VIa, the thermal properties of this polymer are higher and more stable compared to LCPUE VIIa. The types of diisocyanates also contribute to the thermal behavior of LCPUE, where MDI based PU was known for having better order of the rigid chain that approaches the decomposition temperature, giving high melting point to the polymer produced (Jieh & Chou, 1996). As for glass transition, it involves mobility of the chain segments and the Tg will be affected by the mobility restriction on the chain segments, (Suresh et.al., 2008) it therefore explains the varying pattern of the Tg values displayed in Table 1. The decreasing values of Tg can be observed as the length of soft segments increases, indicating that the long chain of polyol gave great flexibility characteristics towards the polymer chains where less mobility

fact that the reaction of all materials took place and LCPUE was successfully prepared.

**3.4. Thermal and liquid crystalline behavior of polymers** 

restrictions occurred and hence resulting in the lower Tg values.

POM was utilized to investigate the type of mesophase by displaying the phase transition that occurred, subsequently providing the polarizing optical microphotographs of the target compounds. The morphology observed on heating and transition temperatures obtained were given in Figures 5 and 6 and the results were summarized in Table 1. It was revealed that all LCPUE showed mesophases upon melting temperature where the thread texture of the nematic phases can be seen. From the photographs taken by POM, the crystal to mesophase transition occurred at temperature ranging from 129 to 181oC. The samples were


**Table 1.** Thermal properties of LCPUE VI (a-c) and LCPUE VII (a-c) by DSC and POM

New Liquid Crystalline Polyurethane Elastomers

Containing Thiazolo [5,4d] Thiazole Moiety: Synthesis and Properties 29

and this indicated semi crystalline character possessed by LCPUE. The results obtained in above range also provide details related to the d-spacing of 3.56 and 4.92 Å, thus supporting the characteristic of nematic liquid crystalline phase (Jeh & The, 1994) as displayed through

**Figure 7.** X-ray diffraction scales of LCPUE VI (a-c) and LCPUE VII (a-c)

arranged as LCPUE VIa>VIIa>VIb>VIIb>VIc>VIIc.

Thermal stability of prepared LCPUE was investigated by thermogravimetric analysis (TGA). Incorporation of liquid crystalline properties into the polymer structure would enhance the thermal properties (Jahromi et.al., 1994) and the theory has proved to be applicable from the results obtained. This may be partly due to favorable interactions between hard domain interface and the liquid crystalline phase. All synthesized LCPUE possessed good thermal stabilities, however, PU elastomers eventually undergo thermal degradation when exposed to high temperatures. Degradation process occurred in two step pattern where the initial degradation occurs in the hard segment involving the urethane linkages, while the second stage indicated the degradation of soft segments. TGA curves in Figure 8 demonstrated the thermal degradation of all LCPUE prepared where 10% weight loss of LCPUE occurred at about 315-341oC and the maximum degradation temperature was in the range of 430-470oC, signifying a high thermal stability property. Furthermore, it can be observed that LCPUE VIIc demonstrated the lowest degradation temperature among the others and this proved that the length of polyethylene glycol (soft segment) influenced the thermal stability of LCPUE where the order of LCPUE due to their thermal stability can be

POM.

**Figure 5.** Polarized optical images of (a) LCPUE VIa (181oC), (b) LCPUE VIb (162 oC) and (c) LCPUE VIc (133 oC)

**Figure 6.** Polarized optical images of (a) LCPUE VIIa (170 oC), (b) LCPUE VIIb (148 oC) and (c) LCPUE VIIc (129 oC)

X-ray diffraction analysis of LCPUE was conducted at room temperature to obtain information on both the mesophase structure and crystallinity of LCPUE. The measurements exhibited several peaks in the range of 2θ= 15 – 25o as observed in Figure 7 and this indicated semi crystalline character possessed by LCPUE. The results obtained in above range also provide details related to the d-spacing of 3.56 and 4.92 Å, thus supporting the characteristic of nematic liquid crystalline phase (Jeh & The, 1994) as displayed through POM.

28 Polyurethane

VIc (133 oC)

VIIc (129 oC)

**Figure 5.** Polarized optical images of (a) LCPUE VIa (181oC), (b) LCPUE VIb (162 oC) and (c) LCPUE

**Figure 6.** Polarized optical images of (a) LCPUE VIIa (170 oC), (b) LCPUE VIIb (148 oC) and (c) LCPUE

X-ray diffraction analysis of LCPUE was conducted at room temperature to obtain information on both the mesophase structure and crystallinity of LCPUE. The measurements exhibited several peaks in the range of 2θ= 15 – 25o as observed in Figure 7

**Figure 7.** X-ray diffraction scales of LCPUE VI (a-c) and LCPUE VII (a-c)

Thermal stability of prepared LCPUE was investigated by thermogravimetric analysis (TGA). Incorporation of liquid crystalline properties into the polymer structure would enhance the thermal properties (Jahromi et.al., 1994) and the theory has proved to be applicable from the results obtained. This may be partly due to favorable interactions between hard domain interface and the liquid crystalline phase. All synthesized LCPUE possessed good thermal stabilities, however, PU elastomers eventually undergo thermal degradation when exposed to high temperatures. Degradation process occurred in two step pattern where the initial degradation occurs in the hard segment involving the urethane linkages, while the second stage indicated the degradation of soft segments. TGA curves in Figure 8 demonstrated the thermal degradation of all LCPUE prepared where 10% weight loss of LCPUE occurred at about 315-341oC and the maximum degradation temperature was in the range of 430-470oC, signifying a high thermal stability property. Furthermore, it can be observed that LCPUE VIIc demonstrated the lowest degradation temperature among the others and this proved that the length of polyethylene glycol (soft segment) influenced the thermal stability of LCPUE where the order of LCPUE due to their thermal stability can be arranged as LCPUE VIa>VIIa>VIb>VIIb>VIc>VIIc.

New Liquid Crystalline Polyurethane Elastomers

Containing Thiazolo [5,4d] Thiazole Moiety: Synthesis and Properties 31

is unusual in conventional PUE (Jeong et.al., 2000). Better phase separation will lead to good mechanical properties; hence the introduction of the mesogens unit as chain extender into

The author would like to thank University Sains Malaysia for short term grant

Abe, A. & Ballauf, M. (1991). Liquid crystallinity in Polymers. John Wiley & Sons Inc, New

Al-Dujaili, A.H.; Atto, A.T. & Al-Kurde, A.M. (2001). Synthesis and Liquid Crystalline Properties of Models and Polymers containing Thiazolo[5,4-d]thiazole and Siloxane

Bagheri, M. & Pourmoazzen, Z. (2008). Synthesis and Properties of New Liquid Crystalline Polyurethanes containing Mesogenic Side Chain Reactive & functional. Polymers,

Barikani, M.; Honarkar, H. & Barikani, M. (2009). Synthesis and Characterization of Polyurethane Elastomers based on Chitosan and Poly(e-caprolactone). Journal of

Doldeny, J.D. & Alder, P.T. (1998). The Mesogenic Index: An Empirical Method for Predicting Polymeric Liquid Crystallinity. High Performance Polymers, Vol.10, pp. 249–272 Issam, A.M. (2007). Synthesis of Novel Y-Type Polyurethane containing Azomethine Moiety, as Non-linear Optical Chromophore and Their Properties. European Polymer

Jahromi, S.; Lub, J. & Mol, G.N. (1994). Synthesis and Photoinitiated Polymerization of

Jeh, C.T. & Teh, C.C. (1994). Study on Thermotropic Liquid Crystalline Polymers -I. Synthesis and Properties of Poly(azomethine-urethane)s. European Polymer Journal,

Jeong, H.M.; Kim, B.K. & Choi, Y.J. (2000). Synthesis and Properties of Thermotropic Liquid

Jia, X.; He, X.D. & Yu, X.H. (1996). Synthesis and Properties of Main-Chain liquid Crystalline Polyurethane Elastomers with Azoxybenzene. Journal of Applied Polymer Science,

Jieh, S.S. & Chou, C.T. (1996). Studies on Thermotropic Liquid Crystalline Polyurethanes.III.Synthesis and properties of polyurethane elastomers by using various

no.304.PTEKIND.6311031 and the fellowship scheme for funding the research.

Flexible Spacers. European Polymer Journal Vol.37, pp. 927-932

Liquid Crystalline Diepoxides. Polymer, Vol. 35, No.3, pp. 622-629

Crystalline Polyurethane Elastomers. Polymer,Vol.41, pp. 1849-185

Applied Polymer Science, Vol.112, pp. 3157–3165

LCPUE can be said to easily induce the matter (phase separation) to occur.

Mohammed Ahmed Issam and Hamidi Mohamed Rashidah

**Author details** 

**Acknowledgement** 

**4. References** 

York, USA

Vol.68, pp. 507–518

Journal, Vol.43, pp. 214-219.

Vol.30, pp. 1059-1064

Vol.62, pp. 465-47

*University Sains Malaysia, Malaysia* 

**Figure 8.** TGA curve of LCPUE VI (a-c) and LCPUE VII (a-c)

#### **3.5. Tensile properties**

Table 2 demonstrates tensile properties of the synthesized LCPUE. As seen, all of the polymers possessed good elastic properties with high elongation at break. Due to the data listed, the higher the molecular weight of the soft segments, the greater the elongation at break, but decrease of tensile strength and tensile modulus can be observed. When the molecular weight of polyol increased, the number of urethane groups in the polyol chain was reduced at the same time, and hence the number of rigid segments is lower, consequently, the possible number of intermolecular hydrogen bonds goes down in which –NH and C=O groups are active (Kro & Pitera, 2008). However, the presence of enhanced rigid and high aspect ratio mesogenic unit as part of hard segment in the synthesized LCPUE, is able to give both high strength and good elastic properties to LCPUE even with long soft segments, which


**Table 2.** Mechanical properties of LCPUE VI (a-c) and LCPUE VII (a-c)

is unusual in conventional PUE (Jeong et.al., 2000). Better phase separation will lead to good mechanical properties; hence the introduction of the mesogens unit as chain extender into LCPUE can be said to easily induce the matter (phase separation) to occur.
