IMIDIZATION AND INTERDIFFUSION OF POLY(AMIC ETHYL-ESTER) PRECURSORS OF PMDA 3,4'-ODA/

Para-, meta-, and mixed isomeric poly( amic ethyl ester) precursors of the polyimide based on pyromellitic dianhydride( PMDA) and 3,4'-oxydi aniline( 3,4'-ODA) were synthesized. The intrinsic viscosity of each o f the isomers was measured in an NMP solution and found to be less tha n 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 temperatu res, T-i using forward recoil spectrometry (FRES). For samples cast fr om a single solvent, either N-methyl pyrrolidone (NMP) or dimethyl sul foxide (DMSO), no difference was observed in the temperature-dependent imidization behavior between the isomers. In all cases the imide frac tion f increased as T-i increased, and reached a value of unity, i.e., full conversion at 400 degrees C. At the same T-i, samples cast from DMSO showed a slightly higher f than samples cast from NMP. FRES and t ime of flight FRES (TOF-FRES) were used to measure the interdiffusion distance, to, of deuterium-labeled tracers into nondeuterated base lay ers of the polyimide of PMDA/3,4'-ODA treated at various T-i. The prim ary determinant of to for all isomers was T-i, and the particular isom er used as either the base or the tracer molecule did not seem to affe ct w. (C) 1998 John Wiley & Sons, Inc.