Recent Progress in Azobenzene‐Based Supramolecular Materials and Applications

Abstract

Azobenzene‐containing small molecules and polymers are functional photoswitchable molecules to form supramolecular nanomaterials for various applications. Recently, supramolecular nanomaterials have received enormous attention in material science because of their simple bottom‐up synthesis approach, understandable mechanisms and structural features, and batch‐to‐batch reproducibility. Azobenzene is a light‐responsive functional moiety in the molecular design of small molecules and polymers and is used to switch the photophysical properties of supramolecular nanomaterials. Herein, we review the latest literature on supramolecular nano‐ and micro‐materials formed from azobenzene‐containing small molecules and polymers through the combinatorial effect of weak molecular interactions. Different classes including complex coacervates, host‐guest systems, co‐assembled, and self‐assembled supramolecular materials, where azobenzene is an essential moiety in small molecules, and photophysical properties are discussed. Afterward, azobenzene‐containing polymers‐based supramolecular photoresponsive materials formed through the host‐guest approach, polymerization‐induced self‐assembly, and post‐polymerization assembly techniques are highlighted. In addition to this, the applications of photoswitchable supramolecular materials in pH sensing, and CO2 capture are presented. In the end, the conclusion and future perspective of azobenzene‐based supramolecular materials for molecular assembly design, and applications are given.

Azobenzene‐Based Conjugated Polymers: Synthesis, Properties, and Biological Applications

“…Azo‐CPs' secondary structure is determined by polymer stereochemical architectural features, such as conformation and configuration, which significantly influence polymer properties in dilute solutions. [ 22 ] Additionally, tertiary structural changes can induce the polymer condensation in liquid crystal or amorphous states, rendering them potentially suitable for incorporation in various devices, such as surface‐relief grating and nonlinear optical (NLO) devices that predominantly rely on bulk azo‐CP structural changes within solid films. [ 23 ]…”

Multiple control of azoquinoline based molecular photoswitches

“…As one of the most employed photochromic switches, azobenzene has received unabated attention due to the simple structure, facile synthesis, large geometric differences between E / Z isomers, and high fatigue-resistance. 1–4 In particular, the change in the molecular shape of azobenzene upon photoactivation offers a powerful strategy for manipulating guest recognition, 5–8 molecular machines, 9–12 supramolecular assemblies, 13–16 and nanoparticles. 17–20 Azoheteroarenes obtained by replacing one or both phenyl with a heteroaryl, 21–24 such as pyridine, 25–28 pyrazole, 29–31 imidazole, 32–34 and thiazole, 35–37 are recently generating strong interest.…”

Photoresponsive Vesicles of Pendimethalin, γ-Cyclodextrin, and an Azobenzene for Controlled Release of a Pesticide

“…Azobenzene can exist in two isomeric forms, trans- and cis- , and these isomers undergo mutual transformation upon exposure to light. This process involves the photoisomerization of azobenzene, resulting in changes in molecular shape and conformation. , Reversible isomerization has attracted extensive attention due to its potential applications in various fields such as optoelectronics, photoinduced luminescent materials, and drug delivery systems. − The trans- isomer of azobenzene is increased stability and reduced reactivity than the cis- isomer, which makes it a suitable candidate for the design of photoresponsive materials with prolonged stability. , Gao and co-workers synthesized self-assembled amphiphilic ternary host–guest complex vesicles by adding CBs, paraquat (PQ), and an azobenzene derivative to ethanol in equal ratios in a one-pot method . In this vesicle, PQ is only released upon exposure to UV or sunlight, inducing conformational flipping of the azobenzene derivatives, leading to vesicle rupture and subsequent separation of the ternary host–guest complex, resulting in the release of PQ with significantly enhanced safety compared to the PQ technical.…”