Dilute solution properties of semi-rigid polyimide precusors

Abstract

A series of polyamic acid precursors to poly[N,N′(p-phenylene)- 3,3′4,4′-biphenyl tetracarboxylic diimide] (BPDA-PDA) have been prepared by offsetting the stoichiometry of the monomers, 3,3′4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), in the polycondensation reaction. The molecular weights of this series were determined by low angle light scattering (LALS) and agreed with the molecular weights predicted by step-growth behavior. LALS measurements have also been correlated with the intrinsic viscosities in both NMP and DMSO. The molecular parameters of the polymers have been found to vary with the solvent. Unusual behavior in both dilute solution viscosity and light scattering measurements may be due to polyelectrolyte effects in undistilled NMP. Comparisons with the more flexible PMDA-ODA (poly[N,N′-(p,p′-oxydiphenylene)-pyromellitimide]) precursors can be made.