Effect of surfactant charge on polymer-micelle interactions: n-dodecyldimethylamine oxide

Abstract

The influence of the nonionic water-soluble polymers poly(vinyl methyl ether) (PVME), poly(propylene oxide) (PPO), and poly(ethylene oxide) (PEO) on the aggregation behavior of n-dodecyldimethylamine oxide (DDAO), at various stages of protonation, has been studied. Critical micelle concentration (cmc) values were determined by the pH method and revealed an increase in stabilization of the micelles by association with PVME and PPO, upon increasing the average charge of the surfactant. The micelles formed from nonionic DDAO are not stabilized by association with PVME or PPO, but association was apparent from the reduction in aggregation number. This reduction in aggregation number is even more pronounced at higher surfactant charge. The results are interpreted in terms of a reduction in electrostatic inter-head-group interaction upon formation of the smaller polymer-bound micelles in the case of the charged surfactant molecules. PEO does not exert any influence on either the cmc or the aggregation number of DDAO micelles at any degree of protonation indicating the absence of polymer-micelle interaction. The effect of neutral and protonated DDAO on the clouding behavior of PVME and PPO has also been studied. 36 refs., 4 figs., 4 tabs.