Endowing a Light-Inert Aqueous Surfactant Two-Phase System with Photoresponsiveness by Introducing a Trojan Horse

Abstract

The ability to modulate the phase behavior of an aqueous surfactant two-phase (ASTP) system reversibly with light is of great importance in both fundamental and applied science. Thus far, most of the light-responsive ASTP systems are based on covalent modification of the component molecules. In this article, we, for the first time, achieve photoresponsiveness in a light-inert ASTP system by physically introducing a phototrigger with the aid of a Trojan horse. The ASTP system formed from sodium laurate (SL) and dodecyltributylammonium bromide (DBAB) does not show light responsiveness by physically mixing a light-responsive azobenzene compound, 2-(4-(phenyldiazenyl)­phenoxy)­acetate sodium (Azo). However, in the presence of the host–guest complex SL@β-CD formed from β-CD and sodium laurate (SL), the ASTP turns quickly into a homogeneous suspension under visible light, which recovers to the original ASTP state again under 365 nm UV irradiation. Because the SL@β-CD complex exists harmonically with the ASTP system, it can be viewed as a “Trojan horse” that becomes fatal only when the encapsulated SL is triggered to release. In the presence of the Trojan horse, the photoresponsiveness of the ASTP system can be manipulated reversibly by alternatively exerting UV and visible light. Using this strategy, we are able to collect trace amounts of oily components from water. The current strategy points out that it is possible to achieve light responsiveness in light-inert systems with a physical method, which may have profound impact on both the fundamental and applied science.

Recent Advances of Photoresponsive Supramolecular Switches

“…By exploiting spatiotemporally and waste‐freely controllable characteristics of light, photoresponsive supramolecular switches have found widespread applications in different areas, such as self‐assembly, [69] drug/gene delivery, [70] and interface chemistry [71] . In this section, the recent advances of supramolecular switches were summarized and categorized by different applications.…”

“…In aqueous solution, amphiphiles usually self-assemble into a variety of structures, such as micelles, [99,106] hydrogel, [100,107] and vesicles, [101,108] which can be applied in cargo trafficking, [102] gene/drug release, [103] fluorescent imprint, [104] rigidity regulation, [105] etc.…”

Enzyme-Responsive Aqueous Two-Phase Systems in a Cationic–Anionic Surfactant Mixture

“…Enzyme-responsive systems are attractive research areas owing to the potential applications in broad fields including drug delivery, − tumor imaging, − bio-inspired assemblies, − and biological materials. − For example, enzymatic hydrogelation formed by polymers − or small molecules has been utilized in enzyme inhibitor screening, − cancer therapy, , and tissue engineering. , However, the enzyme-responsive aqueous two-phase system has been an attractive system for biological material processing due to its gentle high water content environments. − The aqueous two-phase system is a phase separation phenomenon that was observed in polymer solutions initially. − Subsequently, a similar phenomenon termed as aqueous surfactant two-phases (ASTP) was demonstrated with aqueous mixtures of cationic–anionic surfactants. − In an ASTP system, the solution separates spontaneously into two immiscible aqueous phases with a clear interfacial boundary between them, where one phase is rich in surfactants and the other one is the dilute phase. The spontaneous formation of a highly concentrated surfactant solution has enabled the selective concentration of biomolecules, , carbon tubes, , metal ions, and small molecules .…”

Effect of the Substituent Position on the Phase Behavior and Photoresponsive Dynamic Behavior of Mixed Systems of a Gemini Surfactant and trans-Methoxy Sodium Cinnamates

“…Generally speaking, there are two methods of constructing photoresponsive surfactant self-assemblies. One is by introducing light-sensitive groups into the surfactant molecular structure through chemical bonds to synthesize photosensitive surfactants; − the other one is by introducing photosensitive components into surfactant solution directly, in which the noncovalent interaction between surfactants and additives induces the formation of photoresponsive aggregates. However, the photosensitive surfactant synthesis is a complex work with many disadvantages such as energy consumption and time consumption.…”