A new approach for obtaining elastic polyimide-silica composites using a silanol sol prepared from water glass and the imide-containing elastic polymers (IEPs) with polytetramethyleneoxide (PTMO) soft-segment was investigated. Methods of increasing the degree of compatibility between the silica phase prepared from a silanol sol and IEPs obtained via elastic polyureas were examined. Elastic polyimide-silica composites were obtained by the thermal treatment at 200degreesC for 4 h in vacuo after N-methyl-2-pyrrolidone was evaporated from the IEP precursor solutions to which the silanol tetrahydrofuran solution and Bis(trimethoxysilylpropyl)amine (BisA) were added. The use of BisA possessing a reaction site with a carboxylic acid group on the IEP precursors improved the degree of compatibility between the IEPs and silica. Transparent composites were obtained when the concentration of SiO2 was below 22 wt %. FT-IR analyses confirmed that the composite was a segmented hybrid material composed of the PTMO segment, the imide segment, and SiO2. The silica matrix obtained via silanol sol from water glass and the silica matrix obtained by the conventional sol-gel process with an alkoxysilane were essentially the same, and there was no significant loss of silicon due to incomplete hydrolysis of the alkoxides when preparing composites via the water glass route, in contrast to the situation that can occur in the case of the sol-gel route. Dynamic mechanical and thermal analyses suggested that microphase separation between the imide segment and the PTMO segment occurred in the composites and that there was a substantial amount of phase mixing at the same time. The formation of the silica composite had a great influence on the mobility of the segmnets in the phase-mixing domain. TGA analyses indicated that the formation of the 10 wt % silica hybrid gave a composite with a 50degreesC higher degradation temperature. (C) 2004 Wiley Periodicals, Inc.