High-molecular-weight para-type homopolyurethanes prepared by polyaddition of 2,5-tolylene diisocyanate with 4,4‘-bis(ω-hydroxyalkoxy)biphenyls showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane PU6T having [η] 0.82 which was obtained from 4,4‘-bis(6-hydroxyhexyloxy)biphenyl showed T I - LC of 201 °C and T LC - K of 181 °C. In addition, thermotropic liquid-crystalline para-type copolyurethanes PU mn T ( m and n denoting carbon number in alkylene moiety: 2, 6, 8, and 11) were synthesized by polyaddition of the diisocyanate with two 4,4‘-bis(ω-hydroxyalkoxy)biphenyls having different alkylene lengths. For example, PU68T(75/25) had T I - LC of 188 °C and T LC - K of 173 °C. Blends of two para-type homopolyurethanes also exhibited monotropic liquid crystallinity. The liquid crystallinity was examined by differential scanning calorimetry measurement, polarized optical microscope observation, and X-ray diffractometry.
No takes yet. Share an insight, caveat, or question.
Lee et al. (1998) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: