Effect of flexible spacers in liquid crystalline copolyesters containing a non‐linear biphenol moiety

A series of copolyesters 2 containing both linear mesogenic and non‐linear non‐mesogenic aromatic ester units was prepared and characterized for the ability of the latter to either modify or destabilize the liquid‐crystalline (LC) properties of the former. The mesogenic units were formed from the reaction of 1,4‐phenylene diacetate (3) with 4,4′‐decamethylenedioxydibenzoic acid (5), whereas the non‐mesogenic units were formed from reaction of the latter monomer with the diacetate of the non‐linear biphenol, sulfonylbis(1,4′‐phenylene) diacetate (4). The presence of the flexible spacer in each unit allows the copolyesters to form a nematic phase even at a content of non‐mesogenic units as high as approximately 80 mole‐%. Copolyester compositions with mesogenic unit contents approaching this limit for LC behavior appear to form melts which contain both nematic and isotropic phases below the isotropization transitions.