LUMINESCENCE STUDIES OF HYDROPHOBICALLY-MODIFIED, WATER-SOLUBLE POLYMERS .1. FLUORESCENCE ANISOTROPY AND SPECTROSCOPIC INVESTIGATIONS OF THE CONFORMATIONAL BEHAVIOR OF COPOLYMERS OF ACRYLIC-ACID AND STYRENE ORMETHYL-METHACRYLATE

Fluorescence spectroscopy and anisotropy measurements have been used t o study a series of styrene - acrylic acid, STY-AA, and methyl methacr ylate - acrylic acid, MMA-AA, copolymers in dilute methanolic and aque ous solutions. Copolymerization of either STY or MMA with AA has littl e effect upon the rate of intramolecular segmental motion in methanol solutions. In aqueous media, intramolecular hydrophobic aggregation oc curs and restricts the macromolecular dynamics to an extent dependent upon pH, nature of the comonomer, and copolymer composition. The hydro phobic domains formed in these copolymer systems can solubilize organi c guests. In this respect, STY is a more powerful modifier of AA-based polymer behaviours than is MMA. In general, the hydrophobic modificat ion increases the solubilization power of the resultant polymer. Furth ermore, the copolymers retain their solubilization capacities to highe r values of pH the more hydrophobic the comonomer and the greater its content in the copolymer. The interiors of the hydrophobic aggregates reduce the mobilities of occluded guests: the microviscosities of the domain interiors depend upon the nature of the hydrophobe, pH, and cop olymer composition.