Preparation and characterization of organosoluble polyimide/BaTiO3 composite films with mechanical- and chemical-treated ceramic fillers

Organosoluble polyimide (PI)/barium titanate (BaTiO3) hybrid composites using different types of treated ceramic powders were prepared and investigated for their dielectric performance. The soluble coPI poly(p-hydroxy-imide) (PI-2) constituted by 4,4'-oxydiphthalic dianhydride/2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane/4,4'-oxydianiline exhibited a higher dielectric constant (K) of 7.4. The ceramic fillers used in the study were multi-doped self-synthesized BaTiO3 (SS-BT) and commercially available BaTiO3 powders. Up to 50 vol% ceramic fillers were added to the PI, and the resulting dielectric properties were studied. The BaTiO3 fillers underwent particle-size refinement using planetary ball milling and surface modifications through the oxidation of hydrogen peroxide and by grafting with a coupling agent of 3-glycidoxypropyltrimethoxysilane. The highest K-value obtained from the PI-2/SS-BT composites was 52 at a 50 vol% filler content. However, the high-K advantage of SS-BT for hybrid composites is greatly deteriorated by surface modification of the OH- group covering the fillers. Polymer Journal (2012) 44, 1131-1137; doi:10.1038/pj.2012.79; published online 16 May 2012