Orientational Elastic Deformations of Main-Chain LC Aromatic Polyesters and Low Molecular Weight Nematics in a Magnetic Field

Abstract

Orientational elastic deformations in a magnetic field were investigated in the nematic phase of polyphenylterephthaloyl-bis-(4-oxybiphenyl-4′-carbonyl), polylterephthaloyl-bis-(4-oxybiphenyl-3′-carbonyl), and their low molecular weight analogues. Temperature dependences of birefringence Δn were obtained and used to evaluate the degree of orientational order S. The splay and bend elasticiy constants, K1and K3, were determined. The elongation of the rigid mesogenic core in polymer molecules leads to an increase in the K3/K1 ratio, just as in the case of low molecular weight nematics. No effect of molecular weight on the values of Δn and Ki was detected.