Synthesis and Characterization of Perfectly Alternating Segmented Fully Cyclized Polyimide Siloxane Copolymers

Abstract

Perfectly alternating segmented, fully cyclized, poly(siloxane-imide) copolymers were synthesized and characterized as new materials. The reaction utilized the transimidization of aminopropyl terminated polydimethyl siloxane oligomers with aminopyridine capped polyimides based on oxydiphthalic anhydride and bisaniline P. The reaction was conducted in refluxing chlorobenzene at about 130°C. Transimidization processes appear to be quite rapid under these conditions, and high molecular weight copolymers were achieved in times as short as 10 minutes. The resulting copolymers could be cast or melt pressed into transparent films whose mechanical properties reflected the compositions and block molecular weights. In general, the reactions proceeded smoothly under homogeneous conditions in chlorobenzene and produced materials with glass temperatures somewhat depressed from the 240°C value of the controlled polyimide. The method allows excellent control of the microphase morphology, which is a function of block size and interaction parameters. The synthesis and characterization of these materials will be discussed and compared to the more widely studied randomly segmented copolymers which had been prepared in our labs and elsewhere.