Wormlike micelles formed by ultra-long-chain nonionic surfactant

Wormlike micelles (WLMs) formed by different types of ultra-long-chain surfactants have been well studied except for nonionic ones. Here in this paper, a series of ultra-long-chain nonionic surfactants UCn-350 (n = 18, 22, 24) were synthesized by esterification, and their molecule structures were identified using 1H-NMR, 13C NMR, FT-IR, and GPC. The properties of UCn-350 solution, including the cloud point, critical micelle concentration (CMC), rheological behavior, and micellar microstructure, were systematically investigated. It was found that the aqueous solution properties of UCn-350 are highly dependent on their molecule structures. With lengthening the hydrophobic tail, their CMC values as well as the critical overlap concentration (C*) values of WLMs were decreased, and the viscoelastic micellar solution of entangled linear wormlike chains could be formed in pure water by single ultra-long-chain nonionic surfactant UCn-350, without the addition of any other compounds. The longer the hydrophobic tail is, the strongest the thickening ability is. Such viscoelastic fluids may be a good alternative for the delivery of functional ingredients in food or cosmetics.