Influence of acetic acid and ammonia catalyst on microstructure and properties of fluorinated polyimide-organosilicate hybrids

Abstract

This work investigates the preparation, microstructure and thermal/electrical properties of fluorinated polyimide-organosilicate hybrids utilizing acetic acid and ammonia as the catalysts for sol-gel process to grow organosilicate filler particles. Nano-scale organosilicate was observed in the base-catalyzed hybrids, which was ascribed to the relative inertness of base catalysts in promoting the hydrolysis reaction. This postponed the formation of particles and hence smaller particle size. Electrical measurements found that the base-catalyzed hybrids possess lower dielectric constants (kappa = 2.40 at nominal Si content = 0.4 mol) due to the absence of polar groups and formation of silica xerogels with high porosity in the samples. In both hybrids, leakage current densities increase with the increase of Si content. However, leakage current density of base-catalyzed hybrid was higher than that of acid-catalyzed hybrid at the same Si content due to the smaller particle size and highly porous feature of organosilicate embedded in the base-catalyzed hybrids. (C) 2009 Elsevier B.V. All rights reserved.