Ester groups, photodegradation

The radical copolymerization of cyclic ketene acetal with various vinyl monomers such as styrene, MMA, vinyl acetate, and methyl vinyl ketone could afford the copolymers with ester groups in the main chain (26-28). These copolymers showed enzymatic degradability and photodegradability and are applicable as environmentally degradable materials. 

The process by which a solubility differential between exposed and unexposed areas occurs is well known (74). Photodegradation products of the naphthoquinone diazide sensitizer, eg, a l,2-naphthoquinonediazide-5-sulfonic acid ester (11), where Ar is an aryl group, to an indene carboxylic acid confers much increased solubility in aqueous alkaline developer solutions. 

The majority of the work on the fundamental processes of photodegradation of acrylic polymers has been carried out by Grassie and co-workers (5-7). For radiation with wavelength A > 300.0 nm photodegradation is initiated by absorption of a photon by the carbonyl group of the ester side chains. Subsequent fragmentation depends on local stereochemistry and temperature. The principal modes of fragmentation are described by the Norrish I and Norrish II processes (8). 

The photodegradation of poly(n-butyl acrylate) results In the loss of the n-butyl ester side group to yield crosslinks, carboxylic acid groups, keto and aldo groups, and volatile products including butanol and butene. 

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