PHOTOREGULATED ASSOCIATION OF N-(2-HYDROXYPROPYL)METHACRYLAMIDE COPOLYMERS WITH AZOBENZENE-CONTAINING SIDE-CHAINS

The solution properties of N-(2-hydroxypropyl)methacrylamide copolymers containing photochromic azobenzene side chains were studied by light-scattering methods. While copolymers containing 4.4 and 8.3 mol % azobenzene were water soluble, copolymers with greater-than-or-equal-to 9.3 mol % azobenzene were soluble in water only in the pseudomicellar form. Attempts have been made to influence the copolymer association behavior by UV photoirradiation exploiting the difference in solubilities of trans and cis configurations of azobenzene. It was found that metastable aggregates prepared by a stepwise increase in copolymer concentration in aqueous solutions readily dissociated in response to an external stimulus: UV irradiation. However, thermodynamically stable aggregates demonstrated only a limited response to UV irradiation.