Miscible blends of nitro-substituted polybenzimidazole and polyetherimide

A novel blend system was prepared by blending organosoluble nitro-substituted polyblenzimidazole (NO₂-PBI) and polyetherimide (PEI) in a cosolvent at a moderate condition. It was shown that the NO₂-PBI/PEI blends not only possess tractable processability owing to the enhanced solubility of NO₂-PBI but also retain the desirable features of unmodified PBI/PEI blends. Apparent miscibility in the blends was observed and attributed to hydrogen-bonding interactions between N-H groups in NO₂-PBI and carbonyl groups in PEI. It was revealed that the NO₂-PBI/PEI blends phase-separate upon heating above the glass-transition temperatures. The observed mixing of NO₂-PBI and PEI in a molecular level, although sustainable only in the glassy region, was shown to lend synergy effects to the physical properties of the blends.