Dual‐Responsive Viscoelastic Lyotropic Liquid Crystal Fluids to Control the Diffusion of Hydrophilic and Hydrophobic Molecules

A smart lyotropic liquid crystal (LLC) system was prepared to control the diffusion rate of hydrophilic and hydrophobic molecules. The LLC system is composed of a nonionic surfactant (tetraethylene glycol monododecylether; C₁₂EO₄) and an anionic azobenzene surfactant (Azo‐surfactant). C₁₂EO₄ was the main component of the LLC system. The Azo‐surfactant, which can undergo photo‐isomerization, played the role of trigger in this system. LLC gels formed in a solution comprised of Azo‐surfactant (10 mm ) and C₁₂EO₄ (300 mm ). The LLC gels became broken when more Azo‐surfactant was added (e.g., up to 15 mm ) and the viscoelasticity was lost. Surprisingly, when we used UV light to irradiate the 300 mm C₁₂EO₄/15 mm Azo‐surfactant sample, the gel was recovered and high viscoelasticity was observed. However, under visible‐light irradiation, the gel became broken again. The gel formation could also be triggered by heating the sample. On heating the 300 mm C₁₂EO₄/15 mm Azo‐surfactant sample, the system thickened to a point at which typical gel behavior was registered. When the sample was cooled, the gel broke again. The LLC could be used for controlled release of hydrophilic and hydrophobic molecules, and could be considered as a versatile vehicle for the delivery of actives in systems of practical importance.