On the polarization of chiral main-chain liquid-crystalline elastomers.

A mechanism of developing a polarization in a chiral main-chain liquid-crystalline polymer by aligning the dipoles of the monomers is explored. It is shown that the polarization of a pure liquid crystal elastomer is zero in equilibrium due to rotation of the director in the elastomer. A constraint or specific non-ideality in the elastomer is required to prevent this relaxation of the director in order to realize a non-zero polarization. Three methods that circumvent this result are explored. We consider the effect of an oscillating shear, the pinning effect of the layers in a smectic-A composed of chiral smectogens and a binary mixture of chiral main chains and non-chiral side chains. Each of these methods is shown to produce a polarization, which is much larger than that produced in a piezoelectric alpha-quartz crystal per unit stress.