Ferroelectric elastomers of functionalized polar fillers in polydimethylsiloxane with improved dielectric and ferroelectric properties

Stretchable ferroelectric nanocomposites were prepared by combining the ferroelectric properties of vinylidene fluoride-based homopolymer (PVDF) and its copolymer based on trifluoroethylene (P(VDF-TrFE)) with the elas- ticity of polydimethylsiloxane (PDMS). To overcome the incompatibility of the polar filler with the non-polar matrix, functionalization of the filler nanoparticles was carried out. A detailed study of the composite films using optical, thermal, mechanical, and dielectric methods was made to find the impact of functionalization and to study the structure-property relationships in the 0-3 composites. Functionalization improved the mechanical properties as inferred from the reduced Mullins effect. It also increased the dielectric breakdown strength, which can allow higher poling fields ( E p ). From the scanning electron microscope images and mechanical tests on the composites with 20, 40, and 60 wt % of fillers, 40 wt % was found to be the optimum concentration and was chosen for further measurements. While a 40 wt % PVDF/PDMS composite at room temperature and E p = 5 V/μm showed a pyroelectric ( p ) coefficient of 0.06 μC/m 2 K, its 40 wt % copolymer counterpart for similar conditions showed a higher p (0.4 μC/m 2 K). However, the corresponding PVDF and P(VDF-TrFE) composites showed similar piezoelectric d 31 coefficients. This improved piezoelectric response of the PVDF composite is explained in terms of the additional contribution from Maxwell-Wagner interfacial polarization. A maximum d 31 co-efficient of 8.6 pC/N and 10.1 pC/N was measured for the 40 wt % homo- and co-polymer polar composites, respectively, poled with E p = 20 V/μm and strained at 50% with a frequency of 0.1 Hz.