UV polymerisation of surfactants adsorbed at the nematic liquid crystal-water interface produces an optical response

We have investigated the changes in crossed polariser optical textures produced by adsorption and UV polymerisation of a range of polymerisable surfactants at the interface between a nematic liquid crystal and water. Similar to non-polymerisable surfactants, the adsorption of polymerisable surfactants with sufficiently long hydrophobic tail groups produces a transition from planar to homeotropic anchoring. UV polymerisation of surfactants with a polymerisable group located in the hydrophobic tail region changes the anchoring from homeotropic back to planar. Polymerisation in the hydrophilic headgroup region does not produce an optical transition. We demonstrate that these systems can be used to "write with light" in the interfaces and that they form the basis of a UV sensor device in which the optical response is visible to the naked eye.