The hydrostatic piezoelectric coefficient of PVDF/PMMA blends

The piezoelectric coefficients of polyvinylidenefluoride (PVDF) are known to be strictly dependent on the strength of the applied load. For hydrostatic piezoelectricity, it is shown that this nonlinearity is mainly due to the pressure dependence of the bulk compressibility and that blending with polymethyl methacrylate (PMMA) causes a change of sign of the intrinsic electric moment contribution to the overall piezoelectricity. PMMA molecules deteriorate the orientation correlation between the PVDF electric moments in the interface between the amorphous and crystalline phases, and this activity is enhanced by compression. The theoretical background of piezoelectric coefficients is reviewed, and the sample materials, high-pressure investigations, and X-ray and infrared measurements are discussed.<
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