Polydimethylsiloxanes (PDMS) have recently been used as dielectric elastomer materials in electromechanical actuators. When they are soft enough, electric fields can change their shape. However, due to their low dielectric permittivity, large electric fields are required to induce a change. The approach presented here is to chemically modify silicones with cyanopropyl groups in order to increase their permittivity. Samples containing repeat units with cyanopropyl groups from 3 to 23% were synthesized, different methods being employed. The prepared polymers were cross-linked into thin films. The dielectric permittivity of these films increased from 2.4 (for the silicone matrix) to 6.5 for a film containing about 23% of cyanopropyl repeat units. The most promising materials were further optimized to meet the requirements for actuators and their electromechanical properties were investigated. Material A for example, which is a blend of PDMS and cyanopropyl-modified silicone, has a permittivity of 3.5 and higher moduli of elasticity as compared to the matrix but nevertheless shows 10% actuation strain at 40 V μm−1 which is a factor of 3.8 larger as compared to the matrix (2.6% actuation strain at the same voltage).

Polysiloxanes were modified by (co-)hydrosilylation with γ-cyanopropyl and hexyl groups, to finely tune their composition and properties, especially dielectric permittivity, as a way towards active components in dielectric elastomer transducers. Un-modified Si–H groups can be further used to obtain cross-linked thin films.

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.

Novel polysiloxanes with dielectric properties which are systematically fine-tuned by utilizing thiol-ene post-polymerization reactions of a polymethylvinylsiloxane with various ratios of 1-butanethiol and 3-mercaptopropionitrile is presented.

A series of condensation polymers (polyesters and polyamides) of ferrocene and siloxane derivatives have been synthesized and characterized. Thus, 1,1′-di(chlorocarbonyl)ferrocene (CAFc) and four different siloxane derivativess1,3-bis(aminopropyl)tetramethyldisiloxane) (AP 0 ), R,ω-bis(3-aminopropyl)oligodimethylsiloxane (AP), 1,3-bis(hydroxypropyl)tetramethyldisiloxane (HP 0 ), and 1,3-bis(p-hydroxyphenyleneazomethine-3-propyl)tetramethyldisiloxane (HBS 0 )swere used as monomers for this purpose. A model polyamide was prepared by polycondensation of oxalyl chloride with AP 0 . This was analyzed as such or doped with ferrocene in order to appreciate the influence of the ferrocene units by comparison with the corresponding copolymer containing chemically linked ferrocene in the main chain. Thermal, mesomorphic, viscometric, and solubility behaviors of the obtained compounds were studied. Molecular masses were estimated by GPC. The polymers were investigated by cyclic voltammetry and UV-vis absorption spectroscopy in order to evaluate the redox properties and photochemical behavior.