Abstract
Aromatic poly(amic acid) precursors always form complexes with dipolar aprotic solvents via strong acid/base interaction and are expected to have relatively high glass transition temperatures (Tg's) which are overlapped with or higher than the imidization temperatures, so that their Tg's could not be determined in spite of their wide usages. In the present study, the measurement of Tg was attempted for poly(amic acid) precursors of three different aromatic polyimides synthesized in N-methyl-2-pyrrolidone (NMP) from the respective dianhydrides and diamines: poly(4,4‘-oxydiphenylene pyromellitamic acid) (PMDA−ODA), poly(p-phenylene 3,3‘,4,4‘-oxydiphthalamic acid) (ODPA−PDA), and poly(p-phenylene benzophenonetetracarboxamic acid) (BTDA−PDA). Phase transitions, as well as imidization reactions in the precursor/NMP mixtures, were measured with varying compositions by a newly developed oscillating diffferential scanning calorimetry. Compositions in the mixtures were determined by proton nuclear magnetic resona...
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