Reversible photo-cross-linking of polyvinyl alcohol containing thymine

Abstract

Water-soluble polyvinyl alcohol (PVA) was modified by thymine derivatives, which gave reversibly photodimer by UV irradiation. Photo-cross-linking of the polymer (PVA-Thy) was carried out in film state on quartz plate by irradiation at 280 nm.PVA containing thymine had good sensitivity compared with uracil. Photodimerization of the ester derivative was faster than the acetal derivatives, but the sensitivity was lower because solubility in water was high. Reverse reaction of photodimerization was almost complete, but the reversibility of solubility was not complete. This fact indicated that hydrogen bonding between PVA was formed during photodimerization reactions.