PHOTOCHEMICAL MODIFICATION OF A SIDE-CHAIN COPOLYSILOXANE WITH A CHOLESTERIC PHASE

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