Dielectric and thermal characterization of electroactive sol gel/polymer composites

The dielectric characterization of silica gel-poly (methyl methacrylate)-organic dye composites has identified three relaxation mechanisms which give rise to partially overlapping thermocurrent bands in the range 10-320 K of the Thermally Stimulated Depolarization Currents (TSDCs) spectra: a relatively low intensity relaxation band maximized at around 130 K a broad band around 225 K and intense signals above 275 K. Spectral results show that these relaxations are mainly bulk rather electrode interfacial effects, and are discussed in terms of intrinsic dipolar (e.g. rotations of H₂O molecules and conformational motions of the polymer side chain segments), Maxwell-Wagner-Sillars interfacial polarizations, and other types of compositional/structural defects. Differential Scanning Calorimetry (DSC) analysis of PMMA/Sol-gel composites has shown that the impregnated polymer´s transition temperature increases by about 15 degrees, compared to bulk PMMA. The effect is attributed to hydrogen bonding between the pore surface silanols and the polymer side chains, based on additional Raman and NMR measurements