LIQUID CRYSTALLINITY OF THERMOTROPIC PARA-TYPE HOMOPOLYURETHANES AND COPOLYURETHANES CONTAINING BIPHENYLENE MESOGEN AND THEIR BLENDS

High-molecular-weight para-type homopolyurethanes prepared by polyaddi tion of 2,5-tolylene diisocyanate with 4,4'-bis(omega-hydroxyalkoxy)bi phenyls showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane PU6T having [et a] 0.82 which was obtained from 4,4'-bis(6-hydroxyhexyloxy)biphenyl sh owed TI-LC of 201 degrees C and TLC-K of 181 degrees C. In addition, t hermotropic liquid-crystalline para-type copolyurethanes PUmnT (m and n denoting carbon number in alkylene moiety: 2, 6, 8, and 11) were syn thesized by polyaddition of the diisocyanate with two 4,4'-bis(omega-h ydroxyalkoxy)biphenyls having different alkylene lengths. For example, PU68T(75/25) had TI-LC of 188 degrees C and TLC-K of 173 degrees C. B lends of two para-type homopolyurethanes also exhibited monotropic liq uid crystallinity. The liquid crystallinity was examined by differenti al scanning calorimetry measurement, polarized optical microscope obse rvation, and X-ray diffractometry.