Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]-Modified Patchy Particles

Abstract

Sulfonated surface patches of poly(styrene)-based colloidal particles (CPs) were functionalized with cucurbit[7]uril (CB[7]). The macrocycles served as recognition units for diphenyl viologen (DPV(2+)), a rigid bridging ligand. The addition of DPV(2+) to aqueous suspensions of the particles triggered the self-assembly of short linear and branched chainlike structures. The self-assembly mechanism is based on hydrophobic/ion-charge interactions that are established between DPV(2+) and surface-adsorbed CB[7]. DPV(2+) guides the self-assembly of the CPs by forming a ternary DPV(2+)⊂(CB[7])2 complex in which the two CB[7] macrocycles are attached to two different particles. Viologen-driven particle assembly was found to be both directional and reversible. Whereas sodium chloride triggers irreversible particle disassembly, the one-electron reduction of DPV(2+) with sodium dithionite causes disassembly that can be reversed via air oxidation. Thus, this bottom-up synthetic supramolecular approach allowed for the reversible formation and directional alignment of a 2D colloidal material.

A polyrotaxanated covalent organic network based on viologen and cucurbit[7]uril

“…The thickness of the obtained film was~0.9 nm, which corresponds to the diameter of CB [7] and is consistent with incorporation of the macrocycle within the polymeric product 45 . Notably, increasing the ratio of CB [7] to two equivalents lead to the formation of a precipitate, which can be explained by the formation of a ternary 2:1 (CB [7]) 2 :V 2+ complex 39,46 wherein two CB [7] macrocycles encircle the terminal amino-benzene moities of the viologen and hinder imine-bond formation 39 . FTIR, solid-state NMR, steady-state fluorescence and EPR spectroscopies provided further evidence for the presence of CB [7] within the film.…”

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

“…The hybrid assemblies may also be dissociated by reduction of the DPV moieties. 104,105 Using the same approach, a series of micrometer scaled polymers containing particle clusters and arrays has been obtained by Abell and co-workers upon combining viologenand naphthalene-modified particles in the presence of CB [8]. 106 Gold nanorods may be aligned as wires, using {100} end-functionalized nanorods bearing pendant viologen groups.…”

“…The same principle may be used with colloidal polymers based on poly(styrene). The hybrid assemblies may also be dissociated by reduction of the DPV moieties …”

“…Self-aggregation of polymeric colloidal particles using two hosts, ternary caviplex and diphenyl viologen (DPV). 104,105 Reproduced from reference 105 with permission from the American Chemical Society.…”

Shape‐Shifting Patchy Particles

“…Over the past decade, a series of anisotropic particles, including ellipsoids, rods, cubes, Janus particles, dimpled particles, and patchy particles, have been reported . These anisotropic particles have been assembled into colloidal architectures using a variety of short‐range attractions, including entropic, chemical, and non‐equilibrium forces . Most of these building blocks and assembled architectures, however, are static in nature and lack the ability to adapt and reconfigure their shape and structures upon environmental stimulus, which is a prerequisite for reconfigurable smart materials that can adapt on demand, or to environmental cues, to perform a required function .…”