J. Weilepp et Hr. Brand, UNDULATION INSTABILITY IN SMECTIC-A LIQUID SINGLE-CRYSTAL ELASTOMERS, Macromolecular theory and simulations, 7(1), 1998, pp. 91-96
We present a macroscopic model for the behavior of smectic A liquid si
ngle crystal elastomers (LSCEs) under an external dilatory stress thus
investigating the elastomeric analogue of the undulation instability
in low molecular weight (LMW) smectic A liquid crystals. We show that
the critical wavelength lambda(c), of the expected undulation pattern
is given by an expression quite similar to that obtained for LMW smect
ic A phases. This result provides a possible explanation for the stron
g light scattering (high turbidity) observed by Nishikawa et al. very
recently in thick samples of a smectic A LSCE above a certain threshol
d stress applied parallel to the layer normal in the experiments. We f
ind that, in contrast to the critical wavelength lambda(c),, the thres
hold dilatation epsilon(c), is dominated by the elastic properties of
the smectic LSCE. Thus - as observed in the experiments by Nishikawa e
t al. -epsilon(c), is found to be several orders of magnitude higher t
han in the LMW case.