Photoresponsive Supramolecular Amphiphiles for Controlled Self‐Assembly of Nanofibers and Vesicles

M M U Photoresponsive Supramolecular Amphiphiles for Controlled Self-Assembly of Nanofibers and Vesicles N IC By Chao Wang, Qishui Chen, Huaping Xu, Zhiqiang Wang, and Xi Zhang* A T IO N Supramolecular amphiphiles refer to amphiphiles that are synthesized on the basis of noncovalent interactions. The amphiphilicity of the supramolecular amphiphiles can be tunable between hydrophilic and hydrophobic, thus allowing for controlled self-assembly and disassembly. As a result, supramolecular amphiphile is a useful building block to fabricate soft materials with controlled structures and functions. Moreover, functional groups can be introduced directly by noncovalent interactions, thus significantly reducing the need of timeconsuming covalent synthesis. Recently, a few nanoscale soft materials have been prepared using the idea of supramolecular amphiphile, such as stimuli responsive vesicles, ultra-long nanofibers. Among the self-assembly architectures, onedimensional nanostructures have stimulated special interest for their potential applications as nanowires and biomaterials. One dimensional nanostructures with stimuli responsive properties may be further developed as candidates for smart soft materials. Therefore, the preparation of stimuli-responsive one dimensional nanostructures based on the concept of supramolecular amphiphile is of special importance. Herein, we report a photoresponsive one-dimensional nanofiber on the basis of a supramolecular amphiphile. The supramolecular amphiphile consists of two components (Scheme 1). One component is a pyrene containing surfactant (PYN), and the other is a commercially available photoresponsive malachite green molecule (MGCB). Due to the hydrophobic interactions between pyrenyl group and MGCB molecule, PYN and MGCB can preassemble into a supramolecular amphiphile (PYN-MGCB). Moreover, theMGCBmolecule can change into a hydrophilic cation state in response to UV irradiation, and the noncovalent interactions between the MGCB molecule and pyrenyl group will decrease drastically. Therefore, the PYN-MGCB supramolecular amphiphile will disassemble, further changing the supramolecular nanostructures. The PYN-MGCB complex was prepared by mixing PYN and MGCB with a molar ratio of 1:1 in THF. The solvent was then removed under reduced pressure. The dissolution-evaporation procedure was repeated three times to ensure a complete complexation. The resultant complex was finally dried at room temperature in vacuum. Interestingly, the preassembled complex could readily disperse in water and yielded a transparent solution which was stable for months. As MGCB itself cannot disperse in