Photo-induced phase transition from multilamellar vesicles to wormlike micelles

A novel complex fluid system of tetradecyldimethylamine oxide (C(14)DMAO) mixed with para-coumaric acid (PCA) in water was investigated. The phase behavior was determined in detail; one observed sequentially the L-1-phase (micelles), two-phase L-1/L alpha, L-alpha-phase (vesicles), and L-alpha/precipitates with increasing PCA concentration at constant concentration of C14DMAO. The samples in the regions of micelles and vesicles were characterized by rheological measurements and cryo-TEM observations. Fascinatingly, we found a phase transition from vesicles to wormlike micelles performed via UV-light irradiation. The properties and structures after UV-light irradiation were determined by rheological measurements and cryo-TEM observations to demonstrate the phase transition. To the best of our knowledge, this transition is rarely reported, which could provide a better understanding of the phase transition via light irradiation and find potential applications in drug delivery, biochemistry, and the oilfield industry.