SYNTHESIS AND PROPERTIES OF NEW BLOCK-COPOLYMERS BASED ON POLYDIMETHYLSILOXANE AND TETRAPHENYLETHYLENE-CONTAINING POLYIMIDE

New polydimethylsiloxane (PDMS)-polyimide block copolymers were synthesized by the solution polycondensation of aminopropyl-terminated polydimethylsiloxane, 1,1-bis(4-aminophenyl)-2,2-diphenylethylene, and 3,3',4,4'-benzophenonetetracarboxylic dithioanhydride in pyridine. New 1,3-bis(3-aminopropyl)tetramethyldisiloxane (BADS)-based random copolyimides were also prepared. The inherent viscosities of all the random and block copolyimides were in the range of 0.13-0.90 dL/g in N-methyl-2-pyrrolidone. These copolymers were soluble in N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol. All the BADS-based random copolymers and PDMS-containing copolymers with PDMS content above 42 wt % were soluble in tetrahydrofuran and chloroform. Transparent or somewhat opaque films were prepared by casting from the reaction solutions. The BADS-based random copolyimides had one glass transition temperature (T(g)) in the whole composition ranges, which showed single phase nature of the copolymers. On the other hand, the PDMS-polyimide block copolymers had double T(g)s, indicating phase-separated morphology. The block copolymers containing PDMS content above 73 wt % behaved like a high temperature elastomer. (C) 1993 John Wiley & Sons, Inc.