Micelle Formation of Polyoxyethylene Cholesteryl Ether in Water

Abstract

The critical micelle concentrations and the micellar weights of polyoxyethylene cholesteryl ether, C₂₇H₄₆ (OCH₂CH₂)_nOH (Chol EO_n, n=25 and 30) and polyoxyethylene dihydrocholesteryl ether, C₂₇H₄₈ (OCH₂CH₂)_nOH (Dichol EO_n, n=30) were determined by surface tension measurement and membrane osometry. The critical micelle concentration (cmc) values and the micellar weights of these surfactants are similar in magnitude to those of nonionic surfactants of ethylene oxide adduct type with an alkyl or aralkyl group as a lipophilic group. On the basis of these results, it was concluded that these nonionic surfactants form the usual type of large micelles in water in contrast to the cases of cholic acids and their conjugates which form small aggregates in the relatively high concentration range.