Optical anisotropy of comb-like macromolecules of lateral and semilateral structure

Abstract

Maxwell effect and Kerr effect techniques were used to study the intramoleculare axial ordering of anisotropic side groups of an isolated macromolecule in solution. Three comb-like polymers with a methacrylic main chain were investigated. The side chains contain aliphatic spacers separating the mesogenic fragments R from the backbone. R contains two or three phenylene rings with ester linking groups and cyano end groups. Fragments R are attached to the side chains, by the end or middle-point, through the para- or ortho-phenylene ring. The main-chain conformation in solution was identified to assess the hydrodynamic data using the Gaussian coil approximation. The optical anisotropy of the macromolecule segment was determined and related to the monomer unit structure. The specific Kerr constant obtained in diluted benzene solution of polymer was compared with those of low molecular weight analogues of the polymer mesogenic groups. The mobility and intramolecular ordering of the mesogenic groups in the isolated macromolecules are discussed. These properties are compared with those of comb-like polymers with another type of attachment of mesogenic groups, and with another (siloxane) chemical structure of the backbone chain. The differences in restrictions of side-chain mobility due to the backbone linkage in different types of comb-like polymers are also discussed.