PHOTOPHYSICAL CHARACTERIZATION OF WATER-SOLUBLE STYRENE-GRAFTED POLY(ACRYLAMIDE) COPOLYMERS

Although radiation grafting of styrene to poly(acrylamide) was found to be inefficient in aqueous micellar media, however, hexadecylpyridinium chloride micelles provided a measure of control over the grafted styrene side-chain lengths. Measurements with Poisson fluorescence quenching kinetics indicated that the side chains ranged from 24 to 52 units. Fluorescence fine structure using pyrene as a probe revealed that the styrene side chains give rise to hydrophobic domains in aqueous copolymer solutions. An equilibrium constant of 4 x 10(-7) M was measured for the solvation of pyrene in the hydrophobic sites compared to the aqueous phase. Fluorescence quenching was monitored to show that the copolymers isolate and screen hydrophobic guest molecules from the aqueous phase. Hydrolysis of the poly(acrylamide) backbone resulted in no significant change in the characteristics of the hydrophobic domains, in direct contrast to results reported for water-soluble block copolymers of these monomers.