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Abstract
The influence of the concentration of hydrophilic aerosil particles on the collective dynamic modes of the ferroelectric liquid crystal S‐(‐)‐2‐methylbutyl 4‐n‐nonanoyloxybiphenyl‐4′‐carboxylate near the SmA–SmC* phase transition is investigated by means of dielectric spectroscopy in the frequency range 10−2–107 Hz. For aerosil densities ρs = 0.025, 0.05, 0.08 and 0.15 g cm−3 considerable changes in the dielectric intensities of Goldstone and soft modes are observed. The characteristic frequency of the Goldstone mode slightly increases with increasing concentration of aerosil. The frequency degeneracy occurring in the SmA–SmC* phase transition is lifted in the presence of aerosil and an increase in the frequency gap is observed. Complete disappearance of the Goldstone mode at ρs = 0.20 g cm−3 occurs, along with significant broadening of the soft mode. The results are interpreted as an effect of structure, surface interactions and length scale of the helix in disordered confinement.
Acknowledgements
This work has been supported by the National Fund for Scientific Research Flanders, Belgium (FWO, project G.0246.02). S.A.R. acknowledges the receipt of a senior postdoctoral fellowship from the Research Council of K.U.Leuven. The authors are indebted to K. Lodewyckx for help in DSC measurements.