Chiral Periodic Mesoporous Organosilica in a Smectic-A Liquid Crystal: Source of the Electrooptic Response

Chiral periodic mesoporous organosilica (PMO) materials have been shown to deracemize a configurationally achiral, but conformationally racemic liquid crystal in which the PMO is embedded. In particular, application of an electric field E in the liquid crystal’s smectic-A phase results in a rotation of the liquid crystal director by an angle proportional to E, which is detected optically — this is the so-called “electroclinic” effect. Here we present results from electroclinic measurements as a function of frequency and temperature, which allow us to distinguish the component of optical signal that arises from liquid crystal chirality induced within the PMO’s chiral pores from that induced just outside the silica colloids. Our central result is that the overwhelming source of our electrooptic signal emanates from outside the PMO, and that the contribution from the liquid crystal embedded in the chiral pores is much smaller and below the noise level.