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A series of polar silicones was synthesized in order to compare their dielectric properties. Different substituents with high dipole moment (epoxy, pyridyl, aldehyde, cyano-, nitroazobenzene) were attached by hydrosilylation to a poly(dimethyl-methylhydro)siloxane. Thiol-ene addition on a dimethyl-methylvinyl siloxane copolymer with similar composition was also used for chemical modifications with chloro-or carboxy-derivatives. This approach allowed comparison of properties with emphasis on dielectric behavior measured in liquid state, as a preliminary step in design and preparation of materials suitable for dielectric elastomers. Although a relatively low content of polar groups was used (8%), permittivity values of 5.4 and even 7.4 were achieved (at 10 kHz), either due to the large dipole moment or to the presence of important amounts of moisture. The water sorption capacity of the polar silicones was investigated by dynamic vapor sorption, while structural parameters of model molecules were calculated, in order to correlate the dielectric properties with the polarity/hydrophilicity of the substituents to the silicone chain. A combined effect of the calculated dipole moment, molar polarizability, molar volume, and the measured water sorption capacity on dielectric permittivity was observed.

Polysiloxanes with polar cyano groups were cross-linked with PDMS by a hydrolysis–condensation process. Materials suitable for transducer applications with improved permittivity, good mechanical properties, and high breakdown fields were obtained.

Conductive inks consisting of graphene and carbon black conductive fillers into a polydimethylsiloxane (PDMS) matrix, which can be processed into thin films by screen printing are developed. The influence of filler composition and content on mechanical and electrical properties of the conductive composites is investigated. The best composites were evaluated as electrode material for dielectric elastomer actuators and for piezoelectric sensors. With increasing filler content, the electrical properties of the resulting composites of graphite nanoplates (GNPs) or a binary mixture of GNPs and carbon black (CB) with PDMS (Mw = 139 kg/mol) are enhanced. Hence, PDMS composites filled with GNPs (42 wt.%) or a binary mixture of GNPs/CB (300/150 ratio, 30 wt.% of total filler loading) exhibited constant contact resistance values of 0.5 and 5 Ω determined in life-cycle test, respectively, thus rendering them suitable as electrode materials for piezosensors. On the other hand, dielectric elastomer actuators require more flexible electrode materials, which could be tuned by varying the polymer molecular weight and by reducing the filler content. Therefore, a composite consisting of PDMS (Mw = 692 kg/mol) and a binary filler mixture of GNPs/CB (150/75 ratio, 18 wt.% of total filler loading) was used for producing the electrodes of dielectric elastomer transducers (DETs). The produced DETs with different electrode thicknesses were characterized in terms of their performance. The negligible hysteresis of the electrode materials is favorable for sensor and actuator applications.

Polysiloxane elastomers containing varying mo2009l% of trifluoropropyl groups were investigated in dielectric elastomer actuators.

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Dielectric silicone elastomers able to respond to an electrical stimulus by a mechanical displacement are prepared through a simple one-pot procedure consisting in cross-linking and simultaneous in situ generation of the filler functionalized with polar groups, as reinforcing and dielectric permittivity enhancer. One and the same reagent, (3-chloropropyl)trimethoxysilane (CPTMS), serves as both cross-linker and precursor for the filler. This is incorporated in different amounts with dibuthyltindilaurate (DBTDL) into polydimethylsiloxane-α,ω-diols having molecular masses of 34500 and 125000 g•mol-1 and left for curing in atmospheric conditions. The Fourier Transform Infrared (FTIR) spectra show absorption bands characteristic for silsesquioxane (SSQ) structures formed by converting excess CPTMS, while the Transmission Electron Microscopy (TEM) images reveal biphasic morphology of the resulting material in which formations which we have assumed to be SSQ are distributed within the silicone matrix. The structural aspects and supramolecular organization are investigated by Wide Angle X-Ray Diffraction (WAXD) and Small Angle X-ray Scattering (SAXS) analysis. The influence of the CPTMS amount over the mechanical and dielectric properties of the resulted materials are investigated expecting an improvement of the dielectric permittivity but also a strengthening of material. Lateral strain as a response to an applied voltage on dielectric films is measured.