Abstract
Two novel polypyrrolones (PPys) with asymmetric biphenyl moieties in the main chains have been synthesized from 2,3,3',4'-biphenyl tetracarboxylic dianhydride (a-BPDA) and two aromatic tetra-amines: 3,3',4,4'-tetra-amino biphenyl (TABP) and 3,3',4,4'-tetra-amino diphenyl ether (TADPE) respectively, via soluble poly(amide amino acid) (PAAA) precursors, followed by thermal cyclization at elevated temperatures. The polymerization and curing conditions were studied and confirmed. Asymmetric biphenyl structures endowed the polymers with good combined properties. For example, flexible and tough PPy films with acceptable mechanical properties were obtained. Tensile strengths of higher than 70 MPa and elongations at break of higher than 6% were achieved. The PPy films with a final curing temperature of 350°C exhibited good thermal stability and the 10% weight loss temperatures were 610.3°C for PPy-I, and 607.8°C for PPy-II. The residual weight ratios at 700 °C were higher than 80%. In addition, the PPy films showed good dielectric properties with dielectric breakdown strengths of higher than 100 V · μm -1 and dielectric constants of 3.64 for PPy-I and 3.53 for PPy-II.
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