Enhanced degradation of cellulose acetate film containing diphenyliodonium salt–benzophenone

Cellulose acetate (degree of substitution 2.45) films containing diphenyliodonium salt and benzophenone were prepared and their degradative behavior was examined under simulated solar exposure. Acetic acid generation from the films under irradiation was greater in the co-presence of diphenyliodonium salt and benzophenone than in the sole presence of diphenyliodonium salt. Photosensitization and free-radical oxidization, which are followed by Brønsted acid generation, were postulated as the mechanism for the observed increase of deacetylation. The patterns of decreased molecular weight were different between the films with the diphenyliodonium salt and those with benzophenone; while the films with the diphenyliodonium salt kept a relatively constant molecular-weight distribution, the polydispersity increased in the films with benzophenone during the degradation. Since the synthesized characteristics of those two different patterns of change in molecular-weight distribution were observed in the co-presence of the diphenyliodonium salt and benzophenone, each additive appeared to act independently to lead to main-chain cleavage of cellulose acetate. Therefore, decrease in the molecular weight of cellulose acetate by diphenyliodonium salt did not seem to be enhanced in the co-presence with benzophenone.