The structure of salts of polyamic acids in mixed solvents

The structural arrangement of dilute solutions of comblike N,N-dimethylhexadecylammonium salts of polyamic acids made from 3,3,4',4'-biphenyltetacarboxylic dianhydride and o-tolidine was studied by the polarized-light scattering technique. Experiments were carried out in the mixed solvent DMAA-dioxane with compositions close to polymer precipitation. Using the Debye-Stein statistical theory, the statistical structural parameters characterizing the supramolecular structure were calculated. It was shown that the dimensions of scattering entities substantially exceed the molecular dimensions and increase as the polymer molecular mass and the proportion of DMAA in the solvent blend increases. These entities are fluctuating in nature. There is a certain concentration at which the course of concentration dependence of structural parameters changes. This concentration increases with a decrease in the polymer molecular mass, which is probably due to the involvement of the mechanisms of intermolecular interaction between main- and side-chain segments of comblike salt macromolecules.