Dynamo-optical and electro-optical properties of solutions of diphenyl-substituted poly-para-phenylene terephthalate in polar and non-polar solvents☆

The flow and electrical birefringence in solution of a number of fractions of para-aromatic polyester are studied, using dioxane and dichloracetic acid as solvents. In passing from a non-polar (dioxane) solvent to a polar solvent the optical and hydrodynamic properties of the molecular chain remain unchanged, whereas the electro-optical characteristics undergo sharp changes. The hydrodynamic and dynamo-optical characteristics of the polymer under study in dioxane correspond to the properties of a typical rigid chain polymer, whereas the electro-optical properties are typical of a flexible chain. This unique combination of properties can be explained by the specific dipole structure of the monomer unit and the significant difference in the longitudinal and lateral dipole rigidity of the polymer chain of the polyester under study.