Dual-Stimuli Responsive Single-Chain Polymer Folding via Intrachain Complexation of Tetramethoxyazobenzene and β-Cyclodextrin

Abstract

We synthesize and characterize a triblock polymer with asymmetric tetramethoxyazobenzene (TMAB) and β-cyclodextrin functionalization, taking advantage of the well-characterized azobenzene derivative-cyclodextrin inclusion complex to promote photoresponsive, self-contained folding of the polymer in an aqueous system. We use 1 H NMR to show the reversibility of (E)-to-(Z) and (Z)-to-(E) TMAB photoisomerization, and evaluate the thermal stability of (Z)-TMAB and the comparatively rapid acid-catalyzed thermal (Z)-to-(E) isomerization. Important for its potential use as a functional material, we show the photoisomerization cyclability of the polymeric TMAB chromophore and calculate isomerization quantum yields by extinction spectroscopy. To verify self-inclusion of the polymeric TMAB and cyclodextrin, we use two-dimensional 1 H NOESY NMR data to show proximity of TMAB and cyclodextrin in the (E)-state only; however, (Z)-TMAB is not locally correlated with cyclodextrin. Finally, the observed decrease in photoisomerization quantum yield for the dual-functionalized polymer compared to the isolated chromophore in an aqueous solution confirms TMAB and β-cyclodextrin not only are in proximity to one another, but also form the inclusion complex.

Visible Light-Triggered Microactuators and Dynamic Surfaces from Hydrogels Containing Photoswitchable Host–Guest Complexes

“…Several other azobenzene derivatives have also been reported to form photoreversible complexes with CDs and can offer other attractive properties such as red-shifted absorption spectra, higher conversion at the photostationary state (PSS), and greater thermal stability of the cis isomer. − These properties can allow for greater penetration depth of light, improved compatibility with materials for cell and tissue culture, and more persistent shape changes. In this work, we specifically focus on a methyl thioether-substituted arylazopyrazole (SMe-AAP), first reported by Bhunia, Dolai, and Samata .…”

Functionalized Amphiphilic Block Copolymers and Complex Emulsions for Selective Sensing of Dissolved Metals at Liquid–Liquid Interfaces

“…However, unlike molecular surfactants that freely adsorb and desorb from the interface, the adsorption of a polymeric surfactant is considered to be kinetically irreversible . Consequently, BCPs are anchored to the interface of a complex emulsion and are consistently available for sensing in the bulk phase, usually through interfacial complexation. , To this end, BCPs have previously been successfully incorporated into complex emulsion-based sensors for the detection of various biological and environmental contaminants. For example, Li et al developed a rapid sensing device for Listeria monocytogenes through the installation of Listeria antibodies onto a specially modified BCP incorporated as a surfactant into a complex emulsion system .…”

pH-Triggered Transition from Micellar Aggregation to a Host–Guest Complex Accompanied by a Color Change

“…The construction of a stimuli-responsive nanosystem by the method of supramolecular assembly has attracted extensive attention benefitting from its simple composition, easy adjustment, and good repeatability. − In particular, the use of biocompatible water-soluble macrocyclic compounds, such as cyclodextrin, − p -sulfonatocalixarene, − cucurbituril, − and modified pillararene, − to construct stimuli-responsive supramolecular assemblies has shown many promising applications in the biomedical field. It is worth noting that organs, body fluids, and cell compartments have their unique pH values in living organisms.…”