Synthesis and properties of thermotropic liquid crystalline polyurethane elastomers

High molecular weight thermoplastic polyurethane elastomers (TPEs), which consist of crystalline polycaprolactone soft segment and hexamethylene diisocyanate (HDI)/4,4'-dihydroxy biphenyl (DHBP) based mesogenic hard segment, were effectively synthesized by polyaddition reaction in dimethyl sulfoxide. These TPEs had an enantiotropic mesophase in the hard domain, when the content of hard segment was 40 wt.% or higher. Differential scanning calorimetry, polarizing microscopy, X-ray scattering analysis, dynamic mechanical test, tensile test were carried out to examine liquid crystalline, thermal, and mechanical properties and shape memory effect of these TPEs. The results were discussed and compared with those of previous articles, where low molecular weight HDI/DHBP based polyurethane or polycaprolactone diol/4,4'-diphenylmethane diisocyanate/1,4-butanediol based TPEs were examined. (C) 1999 Elsevier Science Ltd. All rights reserved.