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Photocrosslinking of thymine-based water-soluble polymer films was investigated at varying preparation conditions. Adding salt or decreasing the pH of the solution from which the films were cast resulted in the decreased efficiency of photoimmobilization, while increasing the pH was found to increase the photoimmobilization efficiency. A mechanistic rationale for the observed effects is proposed. [ABSTRACT FROM AUTHOR]

The immobilization of thymine‐containing copolymers of vinylphenylsulfonate (VPS) and vinylbenzylthymine (VBT) on a nonreactive substrate has been investigated. These polymers are environmentally benign, water‐soluble and when irradiated with low levels of UV light undergo a 2π+2π photodimerization reaction of the thymine moieties. These photoinduced dimers form a crosslinked network that renders the polymer significantly less soluble in water. Consequently the irradiated polymer is immobilized on the substrate, allowing removal of unexposed regions by simple aqueous wash. Visualization of the photoresist is done by “toning” the remaining anionic copolymer with the cationic dye methylene blue. By evaluating the color density of the crosslinked, toned films by UV‐Vis spectroscopy, this report describes the impact of copolymer composition and curing conditions on polymer photoreactivity. Mechanistic rationale is proposed. [ABSTRACT FROM AUTHOR]