Tuning the Electromechanical Properties of Silicones by Crosslinking Agent

Five R-trialkoxysilanes, with R: CH3, C6H5, NH2(CH2)(3), Cl(CH2)(3), or NC(CH2)(3) are used as crosslinkers for two polydimethylsiloxane-alpha, omega-diols with different molecular masses (35,000 and 125,000 g.mol(-1)) The crosslinking occurs by condensation at room temperature under the influence of the environmental moisture and in presence of dibutyltindilaurate as a catalyst. After aging, the films are characterized by mechanical testing, dielectric spectroscopy, and thermal analysis. Moisture sorption capacity is evaluated by dynamic vapour sorption analysis, while the morphology of the crosslinked films is observed by scanning electron microscopy in cryo-fracture. The mechanical response to an applied electric field is measured. The results are discussed in correlation with polymeric chain length and the nature of R from crosslinking agent emphasizing in principle an increasing of the dielectric permittivity and actuation with the polarity of the organic group but a worsening of these with increasing length of the polymer chain matrix.