Liquid‐crystalline polyethers and copolyethers based on conformational isomerism, 5. Thermotropic copolyethers based on 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane and flexible spacers containing odd and even numbers of methylene units

Abstract

AbstractThe synthesis and characterization of thermotropic main‐chain liquid‐crystalline copolyethers based on 3‐methyl‐4,4′‐ethylenediphenol [1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyhenyl)‐ethane (MBPE)], which is a flexible rod‐like mesogenic unit or a rod‐like mesogenic unit based on conformational isomerism, and pairs of flexible spacers containing odd and even numbers of methylene units, X, Y, i.e., MBPE‐X/Y, where X/Y = 5/12, 5/10, 5/8, 6/11, 6/9, 4/11 and 4/9, are described. Copolymerization decreases the rate of crystallization and subsequently transforms virtual or monotropic mesophases of homopolymers into monotropic or even enantiotropic mesophases. Both liquid‐crystalline transition temperatures and enthalpy changes of the identical mesophases displayed by copolymers represent weight‐averaged values of the similar parameters of the parent homopolymers. Their extrapolation leads to the determination of the virtual mesomorphic transition temperatures and enthalpy changes of the parent homopolymers.