Abstract
A comparative study has been made of the molecular weight characteristics of poly(4′,4″-diphenylenephthalide) pyromellitimide (PI) prepared by polycyclization of the appropriate polyamidoester (PAE) by different methods. Viscosity measurements along with fractionation results and sedimentation analysis show that transition from PAE to PI by solid phase thermal cyclization is accompanied by a reduction in the intrinsic viscosity [η] and in the weight average degree of polymerization X w , and the MWD broadens to become the most probable. No rise in polydispersity occurs in the case of thermal cyclization of PAE to PI in nitrobenzene, but increases in [η] and X w are observed. In the conversion of PAE to PI in solution in presence of acetic anhydride and pyridine, no changes in [η], X w or in the polydispersity were detectable.
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