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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.

Three series of novel modified polyazomethines were prepared with mesogenic units and varying kinking groups. The effect of the incorporation of the kinking groups on the thermotropic properties of the alternated and random polymers was studied. Structural elucidation was carried out by elemental analysis, infrared (IR), proton nuclear magnetic resonance (1H‐NMR) and UV‐vis spectroscopy. Inherent viscosity of the polymers measured in N,N‐dimethyl formamide (DMF) at 20°C was in the range 0.15–0.44 dl/g. Their molecular weight and molecular weight distribution were determined using gel permeation chromatography (GPC). Mesomorphic properties were studied by differential scanning calorimetry (DSC), hot stage polarizing optical microscopy and the thermal stability was determined by thermogravimetric analysis (TGA). Some polyazomethines exhibited fine grain texture and good mesophase stability. It was observed that the random copolymers had lower melting point and higher mesophase stability than alternated polymers. Copyright © 2006 John Wiley & Sons, Ltd.

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