Static and dynamic surface tension behaviour of a triblock copolymer and a non ionic surfactant mixture

Abstract

Abstract Static and dynamic surface tension measurements have been carried out on mixtures of a commonly used block copolymer Pluronics ® P123 and a non-ionic surfactant polyoxyethelene (9) lauryl ether (C 12 E 9 ) to understand the block polymer-surfactant interactions. The effects of the interaction on the adsorption and micellisation behaviour have also been studied. Three different compositions comprising 3:1, 1:1 and 1:3 molar ratios of Pluronic P123 and C 12 E 9 have been investigated and the results are compared with the data of pure P123 and C 12 E 9 solutions. It has been observed that the nature and magnitude of the polymer surfactant interactions depend on the composition of the mixtures. The mixture containing 3:1 molar ratio of P123 and C 12 E 9 shows synergistic effect with a negative value for the interaction parameter (β), as obtained from the analysis of surface tension data using Rubingh’s model. However, for the other two compositions (i.e., 1:1 and 1:3 molar ratios), the equilibrium surface tension data show premicellar adsorption and aggregation of the surfactant molecules on the polymer chain. The dynamic surface tension (DST) results indicate that the strong polymer surfactant interactions, as reflected in the equilibrium surface tension data, do not modify the DST behaviour significantly from that of pure components. This is attributed to the dominant effect of the polymer adsorption at the interface, during the short time scale studied.