Influence of network formation on time soft-mode in ferroelectric LC elastomers

The frequency and temperature dependence of the complex dielectric constant epsilon* was measured for the smectic C*-smectic A phase transition for a crosslinkable ferroelectric polysiloxane. A stepwise crosslinking shifts th e soft-mode absorption to lower frequencies, while an increase in relaxatio n strength and a broadening of the transition occurs. Whereas the shift of the soft-mode can be simply explained by an increase of viscosity in the re sulting elastomer, the other two effects indicate ran increase in the coope rativity of the soft-mode fluctuations due to the coupling of dipoles in th e network even far from the phase transition.