Hydrogen-Bonding Strength in the Blends of Polybenzimidazole with BTDA- and DSDA-Based Polyimides

Abstract

Blends of solutions of poly[2,2‘-( m -phenylene)-5,5‘-bibenzimidazole] (PBI) with poly(amic acids) (PAA's) synthesized from BTDA (3,3‘,4,4‘-tetracarboxybenzophenone dianhydride) and DSDA (3,3‘,4,4‘-tetracarboxydiphenyl sulfone dianhydride) with 3,3‘-DDSO 2 (3,3‘-diaminodiphenyl sulfone), 4,4‘-DDSO 2 (4,4‘-diaminodiphenyl sulfone), 4,4‘-MDA (4,4‘-methylenedianiline), and 4,4‘-ODA (4,4‘-oxydianiline) were prepared in DMAc solvent and transformed into PBI/polyimide (PI) blends by curing at higher temperatures than the T g s of the blends. The blend systems used in this study were all miscible; evidences for miscibility were optically clear film, a synergistic single T g s at all compositions, and frequency shifts of the functional groups intermediate between those of the constituents. The strength of intermolecular interaction between PBI and various polyimides were measured by means of DSC, DMTA, and FT-IR. From the analyzed data based on the T g diagram, the Fox equation, the k values in Gordon−Taylor equation, and the frequency shifts of the functional groups, interpretation was consistent, implying that the strengths of hydrogen bonding display relatively higher in the BTDA-based blends than the DSDA systems. This difference may be arised from the electron affinity in the spacer between benzophenone carbonyl in BTDA and symmetric sulfone in DSDA.