Research On High Dielectric Constant Polymer Composites

High dielectric constant copper phthalocyanine oligomer(CuPc, with a dielectric constant of 10~5～10~6 at the frequency of 100Hz) was successfully grafted to poly p-chloromethyl styrene(PCMS), which shows a still high dielectric property. In order to obtain higher dielectric constant and higher energy storage density material, this chemically modified PCMS-g-CuPc was used to reinforce PVDF and P(VDF-TrFE) matrix. The work included synthesis, modification of CuPc and preparation, characterization of the composites, summarized as follows:(1) Chemical grafting of CuPc to PCMS was obtained with high grafting rate. The dielectric constant of this modified PCMS-g-CuPc was still as high as CuPc.(2) Several kinds of high dielectric constant composite films were prepared. The distribution property of PCMS-g-CuPc in PVDF and P(VDF-TrFE) matrix was improved according to the microscope observation. A new"cell"structure was seen too, as the 20nm CuPc particles were covered by PCMS chains in PCMS-g-CuPc. The new structure of PCMS-g-CuPc solved the problem of large size and serious conglomeration of CuPc in matrix.(3) With a much improved distribution property and decreased size of filler, the interface coupling effect was reinforced. The PCMS-g-CuPc/matrix composite films showed increased dielectric constant and decreased dielectric loss compared with CuPc/matrix composite. The break down field as well as the electric energy density of the modified composite was also improved.(4) Hot-pressed films were prepared to remove the matrix deposition layer formed during the solution-cast process. The dielectric constant improvement of the hot-pressed films was obvious because of the elimination of the polymer lamel and the homogeneous distribution of PCMS-g-CuPc in matrix.(5) According to the percolation theory, chemically-modified-MWNT/PVDF composite films are prepared and characterized to obtain high dielectric constant composite reinforced by MWNT.