DIFFERENCES BETWEEN DYNAMIC AND EQUILIBRIUM SURFACE-TENSION OF (OXYETHYLENE)-POLY(OXYPROPYLENE)-POLY(OXYETHYLENE) BLOCK-COPOLYMER SURFACTANTS (POLOXAMERS P407, P237, AND P338) IN AQUEOUS-SOLUTION

Poloxamer surfactants are macromolecules with complex interfacial beha vior. Although a number of studies of equilibrium surface tension have been published recently, there is little information on the diffusion of these large molecules to the air-liquid interface, Because most su rfactants are used in dynamic systems, the diffusion to the surface ca n be critical in controlling performance. In this study a maximum bubb le pressure method was used to study dynamic surface tension (DST) of Poloxamer P407, P237, and P338, at a range of bubble rates (surface ag e) and concentrations, at either 25 or 35 degrees C. The DST did not c hange at the critical micelle concentration and also did not vary in t he same manner as the equilibrium surface tension (EST) with respect t o temperature. It was concluded that DST behavior of the surfactants w as most closely related to the poly(oxyethylene) content and/or total molecular weight of the surfactants, whereas the micellization and hen ce the EST were more closely related to the poly(oxypropylene) content .