Synthesis and Structural Characterization of Polyimide Containing Diphenylsiloxane Unit

A random copolymer composed of poly(dimethylsiloxane) (PDMS) and poly(diphenylsiloxane) (PDPS), with a controlled molecular weight and a narrow molecular weight distribution, was synthesized. This copolymer, PDMS-r-PDPS, was incorporated into polyimide to create PI(PDMS-r-PDPS) through a two-step chain-end modification process, polycondensation with 4,4'-biphenyltetracarboxylic dianhydride (BPDA), and subsequent heat treatment at 240 ℃. The resulting PI(PDMS-r-PDPS) was formed into a self-standing film, exhibiting a 5% weight loss temperature of 432 ℃ and a glass transition temperature of -32.5 ℃ originating from the PDMS-r-PDPS chain's glass transition. Wide-angle X-ray diffraction (WAXD) analysis revealed that the synthesized PI(PDMS-r-PDPS) possessed an amorphous structure coexisting with a slightly ordered structure.