PROPERTIES OF THERMOPLASTIC POLYURETHANE ELASTOMERS CONTAINING LIQUID-CRYSTALLINE CHAIN EXTENDER (I) SYNTHESIS AND PROPERTIES OF HARD SEGMENTS

Polyurethanes prepared from 1,6-diisocyanate hexane (HDI) and 2,4-toly lene diisocyanate (2,4-TDI) with liquid crystalline chain extender 4,4 '-bis(n-hydroxyalkyloxy)biphenyl (n-PBP, n = 2, 3, 6) were reported. C haracterizations of monomers and polymers were performed by infrared s pectroscopy (IR), H-1-NMR, solid-state C-13-NMR, and elemental analysi s. The phase transition behaviors of polyurethanes were investigated b y Global TSC, DSC, and polarized microscopy (POM). Our results showed that monomers 4,4'-bis(n-hydroxyalkyloxy) biphenyl exhibit smectic typ e mesophase. It was observed that the longer the spacer length of poly urethanes, the higher the chain mobility, the larger DOD (degree of di sorder) value and the lower the relaxation time. Also the phase transi tion temperature of polyurethanes decreases with increasing spacer len gth. DSC measurements and texture observations indicated that H2, H3, H6 and T6 exist in both mesophase and crystal phase. Quantitative anal ysis of temperature dependence hydrogen bonding revealed that hydrogen bonded content (X-b) Of the C=O group for all samples decreased with increasing temperature. For the H series, both X-b and Delta H decreas e with increasing spacer length of the mesogenic diol. (C) 1998 Elsevi er Science Ltd. All rights reserved.