Structure–property correlations in some nematic main–chain polyesters

Abstract

The homologous series of thermotropic nematic main-chain polyesters [graphic omitted] has been investigated. In the case of even values of n, a smectic phase appears at n= 18. An odd–even oscillation of nematic order parameters associated with the mesogen is observed near the clearing temperature, T_c. At the same time, in the vicinity of T_c, the relative order of mesogen and spacer is approximately the same for odd and even values of n. In unoriented specimens of polymer with spacer length n= 10, a layered structure develops progressively with increasing chain length, the sharpness and intensity of the SAX diffraction peak increasing with molecular weight. However, the degree of order remains that of a cybotactic nematic, based on measurements of the complex viscosity and miscibility behaviour. No SAX diffraction peak is observed with spacer length n= 7.