Light-Click <i>In Situ</i> Self-Assembly of Superhelical Nanofibers and Their Helicity Hierarchy Control
Liang Chen, Xuefeng Li, Qiang Yan
Abstract
In situ self-assembly has emerged as a powerful technology in preparation of nanoparticles owing to its solution-processing-free advantage and scalable production. This new technology allows us to facilely obtain a wide range of nanoobjects of architecture and dimension, including spheres, cylinders, vesicles, and tubes; however, it has limitation in the construction of sophisticated superstructures such as helix or superhelix. Here, we describe a new in situ self-assembly method, light-click in situ self-assembly, which can induce the concurrence of polymer coupling and self-assembly through photoclick chemistry. We use this technique to the direct synthesis of helical assemblies. Using two clickable molecules as the reactive precursors, their photoligation can synchronize with their self-assembly process and in situ fabricate ergodic helical nanostructures with chiral bias, evolving from nonhelical filaments to single-stranded helical fibrils to multistranded helical fibrils to complex superhelical fibers. Such helically hierarchical shape evolution is dependent on the photoreaction extent. Quantifying the relationship of reaction conversion and resulting morphology can establish a full phase diagram of helical self-assembly. Moreover, utilizing this strategy, one can on-demand pause and resume the assembly process by switching on and off the light stimulus in order to achieve temporal control of the helicity hierarchy.