Xd. Jia et al., SYNTHESIS AND PROPERTIES OF MAIN-CHAIN LIQUID-CRYSTALLINE POLYURETHANE ELASTOMERS WITH AZOXYBENZENE, Journal of applied polymer science, 62(3), 1996, pp. 465-471
Liquid crystalline polyurethane elastomers (LCPUE) were synthesized by
a two-step block copolymerization reaction. The main-chain LCPUE were
based on two azoxybenzene-type mesogenic diol chain extenders (HA(2)
and HA(6)), a poly(tetramethylene oxide) (PTMO) soft segment, and diff
erent diisocyanates, including 4,4'-diphenylmethane diisocyanate (MDI)
, toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI). Th
e polyurethanes were characterized by FTIR, DSC, DMA, WAXD, UV, and po
larized optical microscopy. Most of the polyurethane samples exhibited
nematic thermotropic liquid crystal behavior and had physical propert
ies typical of thermoplastic elastomers. The liquid crystal properties
were strongly related to the interaction between the hard and soft se
gments of the poly urethane. As the compatibility of the soft and hard
segments increased, the thermal stability of the liquid crystal phase
and the transition temperatures decreased and the range of the transi
tion became narrower. (C) 1996 John Wiley & Sons, Inc.