Preparation and Properties of Hyperbranched Aromatic Polyamide-Silica Composites by Sol-Gel Method

Abstract

Hyperbranched aromatic polyamide-silica composites were prepared using the sol-gel method, starting from tetraethoxysilane (TEOS). Three methods were employed for the preparation of the composites. The first method involves adding TEOS to the solution of hyperbranched aromatic polyamide in the mixture of DMF and formic acid (DMF method). In the second method, hyperbranched aromatic polyamide functionalized with a silane coupler was used instead of unmodified polyamide (coupling method). The third method implies the use of trifluoroacetic acid (TFA) instead of DMF (TFA method). In all cases the composite films were prepared by casting the solution onto a Teflon plate and subsequent heating. Translucent and transparent composite films were prepared by the DMF method, depending on the silica content. The transparency of the composite films was improved by the use of the silane coupler (coupling method). It was found that the TFA method is suitable to prepare transparent composite films in a wide range of silica content. Silica particles were not observed for all of the transparent films by SEM measurements. Since TFA also shows catalytic effect on the sol-gel process, thermal properties of the composite films by the TFA method were improved in comparison with the films prepared by the DMF method.