Abstract
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. Our PI/BaTiO3 hybrid composites were prepared by mixing the organosoluble PI derived from one-step polymerization with BaTiO3 in dimethylacetamide, screen printing the pastes to form composite films and drying at 90 °C for 24h. The low-temperature process is a key for the PI-based flexible devices to be integrated with flexible electronics. The reported PI/BaTiO3 dielectric films were prepared by a two-step process, which needed to be further imidized at 300 °C.
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