Macromolecules, Vol.28, No.7, 2165-2171, 1995
Thermotropic Polyurethanes Prepared from 2,5-Tolylene Diisocyanates and 1,4-bis(Omega-Hydroxyalkoxy)Benzenes Containing No Mesogenic Unit
Thermotropic liquid-crystalline polyurethanes were synthesized by the polyaddition reaction of para-substituted 2,5-tolylene diisocyanate (2,5-TDI) with 1,4-bis(omega-hydroxyalkoxy)benzenes (BHBm : HO(CH2)(m)OC6H4O(CH2)(m)OH; m is the carbon number of the hydroxyalkoxy group). Intrinsic viscosities of the polymers were in the range of 0.22-0.41 dL/g. Polyurethanes 2,5-TDI/BHBm’s (m = 3, 5, 6, 8) prepared from BHBm and 2,5-TDI, exhibited monotropic Liquid crystallinity, although these polyurethanes contained no mesogenic core unit. For example, polyurethane 2,5-TDI/BHB5 with [eta] = 0.33 prepared from 1,4-bis(5-hydroxypentoxy)benzene (BHB5) and 2,5-TDI exhibited an anisotropic phase from 119 to 51 degrees C. In contrast, for the series of 1,4-PDI/BHBm (m = 2, 3, 5, 6, 8, 11) having no substituent in a phenylene unit, no explicit mesomorphic behavior was observed by DSC measurement and polarized microscopic observation.
Keywords:LIQUID-CRYSTALLINE POLYURETHANES;SIDE-CHAIN;MULTIFUNCTIONAL ISOCYANATES;2;6-TOLYLENE DIISOCYANATE;POLY(ESTER AMIDES);FLEXIBLE SPACER;6 METHYLENE;POLYMERS;PHASE;BIPHENOL