Imide-dimethylsiloxane block copolymers: Design and synthesis of a permanent buried oxygen ion etch barrier

Abstract

Imide-siloxane multiblock copolymers were investigated. A key feature of these copolymers is the preparation of bis(aminopropyl) oligomers via anionic ring-opening polymerization. The molecular weights of the oligomers ranged from 1000 to 5000 g/mol. The oligomers were coreacted with 4,4′-oxydianaline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester chloride in a N-methyl-2-pyrrolidone/THF-solvent mixture in the presence of N-methylmorpholine. The resulting amic ethyl ester siloxane copolymers were isolated and washed to remove homopolymer contamination. Copolymer compositions, determined by 1H-NMR, ranged from 20 to 65 wt % siloxane content and the measured compositions were close to those charged. Solutions of the copolymers were cast and cured (350 °C) to effect imidization, producing clear films. The films showed tough ductile mechanical properties with moduli varying with siloxane content. The copolymers displayed good thermal stability with decomposition temperatures in the proximity of 450 °C. Multiphase morphologies were observed irrespective of siloxane block lengths or compositions.