LAYER STRUCTURES 11 - CHOLESTERIC POLYESTERS DERIVED FROM ISOSORBIDE,2,5-BIS(DODECYLOXY)TEREPHTHALIC ACID AND 4,4'-DIHYDROXYBIPHENYL

One non chiral homopolyester and five chiral copolyesters were prepare d by polycondensations of 2,5-bis(dodecyloxy)terephthaloylchloride and 4,4'-dihydroxybiphenyl or mixtures of this diphenol and isosorbide. T he resulting polyesters were characterized by viscosity measurements, elemental analyses, H-1 n.m.r. measurements, optical microscopy, DSC-m easurements and X-ray measurements with synchrotron radiation at varia ble temperatures. If more than 20% of the 4,4'-dihydroxybiphenyl were replaced by isosorbide the copolyesters lost their thermotropic charac ter. All polyesters with 20% or less isosorbide proved to be semicryst alline thermotropic materials showing three phase transitions: firstly a melting process (T-m1), secondly a transition from a sanidic LC-pha se to a normal nematic or cholesteric melt (T-m2) and finally to the i sotropisation (Ti). The copolyester containing 10% isosorbide was capa ble of forming a Grandjean texture. (C) 1998 Elsevier Science Ltd. All rights reserved.