THE INFLUENCE OF A PHASE-TRANSITION IN POLY(OXYETHYLENE) POLY(OXYPROPYLENE)/POLY(OXYETHYLENE) BLOCK-COPOLYMER SURFACTANTS ON THE PROPERTIESOF MATERIAL ADSORBED FROM DILUTE AQUEOUS-SOLUTION/

In this study the adsorption of poloxamer block copolymer surfactants to polystyrene latex has been studied at a range of temperatures. It h as been noted previously that the adsorption first falls, then rises a nd falls again as the temperature is increased, due to the existence o f a phase transition in aqueous solutions of these surfactants at spec ific temperatures, which may be a critical micelle temperature. The pr esent study shows that the hydrophobicity of the surface changes in a manner related to the amount of poloxamer adsorbed (i.e. is greatly in fluenced by the temperature of adsorption in relation to the transitio n temperature). The coating layer thickness, however, is essentially u nchanged by the temperature of adsorption (i.e. not related to the amo unt adsorbed), but is influenced by the temperature at which the sizin g was undertaken. This is due to dehydration of the poly (oxyethylene) with increasing temperature. The data presented here provide a possib le explanation for the changes in biological distribution of poloxamer coated particles which occur when they are injected into animals.