Imidization and interdiffusion of poly(amic ethyl ester) precursors of PMDA/3,4′-ODA

Abstract

Para-, meta-, and mixed isomeric poly(amic ethyl ester) precursors of the polyimide based on pyromellitic dianhydride (PMDA) and 3,4′-oxydianiline (3,4′-ODA) were synthesized. The intrinsic viscosity of each of the isomers was measured in an NMP solution and found to be less than corresponding isomers derived from PMDA and 4,4′-oxydianiline (4,4′-ODA) precursors with comparable molecular weight. The imidization and solvent retention were measured as a function of imidization temperatures, Ti using forward recoil spectrometry (FRES). For samples cast from a single solvent, either N-methyl pyrrolidone (NMP) or dimethyl sulfoxide (DMSO), no difference was observed in the temperature-dependent imidization behavior between the isomers. In all cases the imide fraction f increased as Ti increased, and reached a value of unity, i.e., full conversion at 400°C. At the same Ti, samples cast from DMSO showed a slightly higher f than samples cast from NMP. FRES and time of flight FRES (TOFFRES) were used to measure the interdiffusion distance, w, of deuterium-labeled tracers into nondeuterated base layers of the polyimide of PMDA/3,4′-ODA treated at various Ti. The primary determinant of w for all isomers was Ti, and the particular isomer used as either the base or the tracer molecule did not seem to affect w. © 1998 John Wiley & Sons, Inc.