LAYER STRUCTURES 12 - CHIRAL SANIDIC POLYESTERS DERIVED FROM 2,5-BIS(HEXADECYLOXY)TEREPHTHALIC ACID, 2,5-BIS((S)-2-METHYLBUTOXY)TEREPHTHALIC ACID AND 4,4'-DIHYDROXYBIPHENYL

Three homopolyesters were prepared by polycondensation of 4,4'-dihydro xybiphenyl and 2,5-bis(n-octyloxy)-, 2,5-bis(dodecyloxy)- or 2,5-(hexa decyloxy)terephthaloylchloride. Furthermore, several copolyesters were synthesized from 4,4'-dihydroxybiphenyl and mixtures of 2,5-bis(hexad ecyloxy)terephthaloylchloride and 2,5-bis((S)isopentyloxy)terephthaloy lchloride. All polyesters were characterized by inherent viscosities, elemental analyses, H-1 n.m.r. spectroscopy, d.s.c. measurements, dyna mic mechanical analyses (DMA), WAXS powder patterns at various tempera tures and optical microscopy. Two liquid crystalline (LC) phases were detected for the homopolyesters and most copolyesters: a viscous sanid ic (biaxial nematic) phase and, at higher temperatures, a mobile nemat ic phase. The chiral copolyesters displayed an unusual 'sausage textur e', but never a Grandjean texture. A chiral nematic phase with helical main chains is discussed. (C) 1998 Elsevier Science Ltd. All rights r eserved.