Solution properties of meta and para isomers of polyamic esters

Abstract

This study concerns measurements on the ethyl ester derivative of the PMDA/ODA polyamic acid. The ester derivative has several advantages over the amic acid with regard to characterization. It may be precipitated from the polymerization mixture as a solid without degradation by hydrolysis as occurs for the amic acid. This avoids many of the problems due to solvent impurities reported for solutions of polyamic acids. The ionization of the carboxylic acid group which can complicate characterization of the polyamic acid cannot occur with the ester. Finally, the ester may be prepared in the meta or para catenated form which permits more direct comparison with theoretical predictions as well as an assessment of the effect of catenation on the chain dimensions. Measurements of MW and the second virial coefficient, A2, from low angle light scattering; and intrinsic viscosities for a series of meta and para ethyl esters of PMDA/ODA in NMP are presented. These results are compared with previous results.