THE EFFECT OF GAMMA-IRRADIATION ON THE SURFACE, RHEOLOGICAL AND MICELLAR BEHAVIOR OF THE BLOCK COPOLYMER, TETRONIC-908

The poly(oxyethylene)-poly(oxypropylene) block copolymer, Synperonic (Tetronic) T908, is a poloxamine which forms micelles in aqueous solution over the temperature range 30-50-degrees-C. Photon correlation spectroscopy studies have shown increases of mean micelle size and polydispersity of this poloxamine with increase of solute concentration in aqueous solution, leading eventually to the reversible gelation of the solutions at concentrations above approx. 20% w/w. Exposure of solutions of T908 to doses of gamma radiation up to 1.2 Mrad induced gelation at lower poloxamine concentrations than in nonirradiated systems. Irradiation had no detectable effect on the aggregation number of the micelles or the critical micelle concentration but caused a significant increase of micellar hydration. Temperature increase between 30 and 50-degrees-C caused an increase of aggregation number and a concomitant decrease of micellar hydration in both irradiated and nonirradiated systems. The relevance of these changes in micellar properties to the thermal gelation of T908 is discussed.