Photochemical modification of a side chain copolysiloxane with a cholesteric phase

Using a nematic monomer and a chiral monomer, we have synthesized several cholesteric side chain copolysiloxanes. The chiral monomer contains a photosensitive group which can be racemized or have its chirality removed by a photochemical reaction. The racemization of the chiral monomer proceeds by abstraction of a hydrogen atom from the 2-hydroxyl group of binaphthol. The reduction in chirality of a cholesteric copolysiloxane is proportional to the dosage of ultraviolet (UV) irradiation. The resultant polymer showed an increase in glass transition temperature and a decrease in cholesteric to isotropic transition temperature.