Solvent-dependent conformations and piezoelectricity of the copolymer of vinylidene cyanide and vinyl acetate

Conformations in deuterated dimethyl sulphoxide (DMSO-d 6), dimethyl acetamide (DMA-d 9) and dimethyl formamide (DMF-d 7) solutions for the copolymer of vinylidene cyanide and vinyl acetate, P(VDCN/VAc), have been investigated by using 500 MHz 1H nuclear magnetic resonance spectroscopy. Making use of the vicinal coupling constants, which were obtained from spectral simulation, the conformer populations as well as the conformational energies were calculated with respect to the ϵ-tacticity. The mole fraction of trans conformer around the H AH BC-CH X bond increases with the polarity of the solvent used. The anisotropy of the dipole moment with various conformations for P(VDCN/VAc) was also considered. The calculated dipole moment in the direction of the C(CN) 2 bond dipole was 6 debye for the all- trans conformation along the main chain composed of eight carbons, which amounts to twice that of the other conformations. The effect of casting solvent species on physical properties in a solid film was investigated by measuring the piezoelectric strain constant and the enthalpy relaxation. It was concluded that molecules with an all- trans rich conformation obtained from DMSO solution would be arranged with compact packing, resulting in a large enthalpy relaxation.