Cyclic architectures of polymers have shown unique properties or improved performance owing to the lack of chain ends. Herein, we describe the first example of azobenzene-induced photoresponsive gels based on cyclic polymers fabricated using an azide–alkyne and boronic acid-diol “click” reaction. The properties of cyclic gels with different cyclic polymer sizes were investigated by comparing them with those of linear gels made using polymeric linear precursors. It was observed that the cyclic topology exerted a larger influence on the properties of the gels. Further significant influences exerted by the topology were observed in cyclic gels with a smaller cyclic polymer size. Rheological measurements revealed that the cyclic gels have a higher storage modulus (G′) and loss modulus (G′′) compared to their linear counterparts, indicating that the former is stiffer than the latter. The gel-to-sol transition and photo-healing of the gels induced by azobenzene were observed by irradiation with UV/Vis light. Nevertheless, the cyclic gel with a smaller cyclic polymer size demonstrated a poor photo-responsive behavior owing to the restrictions of transformation of the trans–cis isomer of azobenzene moieties imposed by the cyclic topology. The results in this work showed that the network mesh space, and intramolecular and intermolecular interactions induced by the macrocyclic architecture endow the functional cyclic gels with unique properties.
The construction of stimuli-responsive materials by using naturally occurring molecules as building blocks has received increasing attention owing to their bioavailability, biocompatibility, and biodegradability. Herein, a symmetrical azobenzene-functionalized natural glycyrrhizic acid ( trans - GAG ) was synthesized and could form stable supramolecular gels in DMSO/H 2 O and MeOH/H 2 O. Owing to trans – cis isomerization, this gel exhibited typical light-responsive behavior that led to a reversible gel–sol transition accompanied by a variation in morphology and rheology. Additionally, this trans - GAG gel displayed a distinct injectable self-healing property and outstanding biocompatibility. This work provides a simple yet rational strategy to fabricate stimuli-responsive materials from naturally occurring, eco-friendly molecules.
Photoresponsive gels exhibit various applications because they can change their structures and properties under the stimulation of light. However, the use of photoresponsive gels is limited by solvent evaporation, which compromises their longevity and functionality. Herein, we design a metallopolymer organogel to overcome this challenge. The organo-gel incorporates metal-ligand coordination bonds as reversible, photoswitchable crosslinks within a polyacrylamide network, using high-boiling-point 1,2-propanediol as the solvent. This system exhibits excellent stability against solvent loss and displays fully reversible and photoresponsive behaviors, including gel-to-sol transitions, color change and volumetric expansion/contraction. We use these properties to demonstrate rewritable photopatterning and shape reconfiguration. We also demonstrate that the organogel maintains low solvent evaporation and stable performance even under hightemperature conditions. The metallopolymer organogel design opens avenues for the development of long-lasting, intelligent soft matter for use in demanding applications.
危险品化学品经营许可证（带存储）