The condensation of bisketomethylene monomers with either 4,6‐dibenzoyl‐1,3‐phenylenediamine or 2,5‐dibenzoyl‐1,4‐phenylenediamine catalyzed by acid affords high molecular weight polymers containing the anthrazoline and isoanthrazoline units in the polymer main chain. Base is not an effective catalyst for the production of high molecular weight polymer. The phenyl substitution on the anthrazoline and isoanthrazoline units increases the solubility of these polymers over those in which phenyl substitution is absent. The rodlike character of these polymers, which can be altered by positional isomerism in the chain, has an effect on the solution properties.
The plane strain fracture toughness of polyphenylene sulfide (PPS), tested with different molecular structures such as linear PPS, heat‐treated PPS, and branched PPS, was investigated over a wide range of melt viscosity and crystallinity and compared with other mechanical properties. The fracture toughness of linear PPS increased with increasing melt viscosity, and it reached the highest fracture toughness calculated from linear elastic fracture mechanics (LEFM) observed in this study. In this high melt viscosity region, the linear PPS specimen showed slow crack growth instead of brittle fracture. Although the tensile properties of heat‐treated PPS and branched PPS are the same as those of linear PPS, the fracture toughness of linear PPS is superior. The fracture toughness is affected by the crystallinity of the specimen, and the effect of crystallinity on fracture toughness is smaller than that of melt viscosity and molecular structure.
The piezoelectricity of PVDF thermoelect rets formed with vacuum‐coated aluminum electrodes has been investigated in detail. The piezoelectricity depends on the β‐form crystal structure of PVDF homopolymer and copolymers. However, the piezoelectricity is not attributed to the stress dependence of the spontaneous polarization of β‐form crystals, but rather to the persistent polarization arising from trapped charges. The trapping mechanism is discussed.
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