THERMAL IMIDIZATION BEHAVIOR OF AROMATIC POLY(AMIC DIALKYL ESTER) PRECURSORS DERIVED FROM BIPHENYLTETRACARBOXYLIC DIANHYDRIDE

Poly(amic dialkyl ester) precursors of high performance poly(4,4'-oxyd iphenylene biphenyltetracarboximide) (BPDA-ODA) and poly(p-phenylene b iphenyltetracarboximide) (BPDA-PDA) were synthesized and their thermal imidizations were investigated isothermally and nonisothermally by th ermogravimetry. All precursors showed a two-step imidization behavior, fast imidization at early stage and slow imidization at intermediate and later stage. Kinetic parameters were estimated from the conversion versus time plots with the first-order rate equation. The imidization behaviors observed were interpreted with considering the T(g) variati on, the natures of alkyl leaving group and precursor backbone, and the flexibility of polymer chain. In addition, the onset temperature of i midization and T(g) of precursors were estimated from the imidization kinetic data.