Creation of photo-modulated multi-state and multi-scale molecular assemblies via binary-state molecular switch

Abstract

The creation of photo-modulated multi-state and multi-scale molecular self-assemblies was realized by the ingenuous utilization of a binary-state molecular switch, sodium (4-phenylazo-phenoxy)-acetate (AzoNa). Depending on the irradiation time, the binary state of the azobenzene group (i.e. trans/cis isomerization) can be exploited to generate multi-state nanostructures (including wormlike micelle, vesicle, lamellar structure, small micelle) by the coupling of conventional surfactant CTAB. Meanwhile, the conformation transition of azobenzene at molecular scale (∼Å), stimulated by light input can be amplified to regulate molecular architectures at mesoscopic scale (from nanometer to micrometer), leading to significant changes in solution property at macroscopic scale (naked-eye visible scale). By exposing to UV or visible light, the multi-state and multi-scale molecular self-assemblies can be reversibly controlled. It is proposed that light-triggered structural changes in the dipole moment and geometry of azobenzene group, which impart a significant effect upon molecular packing of surfactant aggregates, were responsible for this peculiar phenomenon.