Micro-structured cellular polydimethylsiloxane (PDMS) materials were prepared by a low-cost molding process allowing us to control geometry and sample size. Cellular structures are charged with a triangular quasi-static voltage with amplitudes between 1 kV and 4 kV and a frequency of 0.5 Hz fixed after having evaluated the conditions enhancing the piezoelectric response of the cellular PDMS. The piezo-electret PDMS material charged at room temperature has a piezoelectric coefficient d 33 of 350 pC/N, which is ten times larger than that of polyvinylidene fluoride. The high piezoelectric coefficient with a very low elastic modulus of 300 kPa makes these materials very useful for wearable device applications. The piezoelectric coefficient d 33 of the samples poled at high temperatures improves thermal stability but reduces PDMS piezoelectret piezoelectricity, which is explained by the structure's stiffness. These results are useful and allow us to set the conditions for the preparation of the piezo-electret materials according to desired applications.

Dielectric and electrical properties correlated with the structure analysis have been studied on 27% semicrystalline parylene-N (-H2C-C6H4-CH2-)n thin films. Transition-phase, AC- and DC-conduction mechanisms, and the MW-interfacial polarization were identified in parylene N at high temperature by experimental and theoretical investigations. The dielectric analysis based on the dc conductivity highlights a temperature of 230 °C as a transition temperature from the α-form to the β1-form. This structure transition is accompanied by a modification on the DC-conduction mechanisms from ionic to electronic conduction in the α-form and the β1-form, respectively. The AC conduction mechanism is governed by the small polaron tunneling mechanism (SPTM) with WH,α = 0.23 eV and a tunneling distance of 7.71 Å in the α-form, while it becomes a correlated barrier-hopping (CBH) mechanism with a WM,β 1 = 0.52 eV in the β1-form. The imaginary part of the electrical modulus formalism obeys the Kohlrausch-Williams-Watt (KWW) model and shows the presence of the interfacial polarization effect. The theoretical Kohlrausch exponent (βKWW) confirms the existence of the transition phase on the parylene N in the vicinity of the 230 °C as deduced by the DC- and the AC-conduction parameters. The correlations between the experimental results and the theoretical models are very useful knowledge and tools for diverse parylene N applications at high temperature.

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