Macroscopic Photo-Responsive Behaviors of Self-assemblies Constructed by Photo-Responsive Small Molecules and Surfactants

Halogen-free surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium alkyl sulfate (C₄mimC₁₂SO₄), was synthesized through ion exchange reaction. The photo responsive system of Gemini surfactant 12-3-12·2Br^－ (Gemini12-3-12)/C₄mimC₁₂SO₄/ trans -OMCA/H₂O was constructed by mixing C₄mimC₁₂SO₄ with Gemini12-3-12, followed by an addition of photosensitive molecules, trans -o-methoxy cinnamate ( trans -OMCA). The photo-responsive behaviors of aqueous two-phase system (ATPS), a specific single-phase system and the anisotropic phase system in the mixture of Gemini12-3-12/C₄mimC₁₂SO₄/ trans -OMCA/H₂O were studied by TEM, UV-vis and dynamic light scattering (DLS). The results show that the mixed system displays good photo responsiveness. For the aqueous two-phase system, in which spherical micelle and wormlike micelle coexist, UV irradiation for a certain period of time promotes the fusion of the spherical-micelle phase and wormlike-micelle phase into another single wormlike-micelle phase. For the single-phase vesicle system, it is separated into a two-phase system of spherical micelle and wormlike micelle after UV irradiation, and the system gradually merges into a single wormlike-micelle phase when the irradiation time is prolonged. The anisotropic system becomes isotropic after exposure to UV irradiation. It is suggested that the macro-phase behaviors of the system can be changed by UV irradiation and the system can undergo a photo-induced phase separation as well as combination.