Self-assembly study of polydisperse ethylene oxide-based nonionic surfactants.

The self-assembly behavior of polyethoxylate-based multicomponent nonionic surfactants was studied. Using the dynamic light scattering method, thermodynamical parameters such as the critical micelle concentration (cmc) and hydrophile-lipophile balance (HLB), as well as the micelle size and micelle size distribution, were determined. The number average molecular weight and number average HLB of the samples were determined by MALDI-TOF-MS and 1H NMR techniques, and the data were evaluated. A connection was found between the HLB and the ln(cmc) value of the samples which can be described by a simple equation. Using this equation and plotting ln(cmc) versus the average number of ethylene oxide units, lines were obtained at different temperatures, and their slope allowed the calculation of the contribution of a single ethylene oxide unit to the Gibbs free energy of micellization.