We demonstrated the modular synthesis of polymer thermosets exhibiting programmed responses that arise from two predesigned functional units: a reversible cross-linker and a selfimmolative linker. The former unit contains a 1,2,3-triazolium moiety that provides the cross-linked network but undergoes dynamic covalent bond exchange via transalkylation, while the latter phenyl-based unit generates a signal-specific elimination reaction that promotes selective de-cross-linking of the entire network. The two units form a functional, dual cross-linked structure after thiol−ene click polymerization followed by a thermal curing reaction, allowing large-scale synthesis. By changing the ratio of functional units, the physicochemical properties of the materials during polymerization can be finely tuned, and adequate combinations result in tailored thermosets that are reversible yet removable. Thus, we were able to reuse the thermosets in bulk, solid state, or restructure without overall structural collapse. Furthermore, by exploiting the designed nature, the materials can be used as a stimuli-responsive adhesive. We observed a high adhesive strength when gluing glass pieces and rejoined them upon heating after they were detached by force. However, exposure to a molecular signal significantly diminished the adhesion under benign conditions, and the joint was easily and irreversibly separated. The design concept and materials presented herein elucidate or advance the chemical concepts for the recycling and disposal of commercial thermosetting plastics when they are no longer needed.

Stomach cancer is a global health concern as millions of cases are reported each year. In the present study, we developed a pH-responsive microrobot with good biocompatibility, magnetic-field controlled movements,...

Polymer membranes represent an attractive platform for energy-efficient gas separation, but they are known to suffer from plasticization during continuous gas-separation processes. This phenomenon is caused by the spontaneous relaxation...

In this paper, a hierarchical design of supramolecular hydrogels comprising two individual supramolecular networks that are capable of exhibiting reversible and programmed behaviors is described. Both component networks are established by (i) conformational transformation of natural polysaccharides and (ii) host–guest interaction between separate polymer chains. Sequential formation of each orthogonal network generates an interpenetrated structure, which results in the formation of biobased, completely noncovalent, double-network hydrogels. Owing to the intrinsic advantages of the cross-linking system, the hydrogel materials demonstrated the reversibility of physical properties in response to heat or light and exhibited macroscopic performance such as self-healing or injectable properties without calamitous structural collapse. In particular, it was possible to demonstrate the superstructured hydrogels as a responsive vector. Selected dye or drug molecules were loaded during the formation of the networks, and sustained release behavior was achieved around body temperature, which could be fairly enhanced upon UV-light irradiation. Also, we were able to develop a three-dimensional, bioprinted, large-scale pattern using the hydrogels as a bioink. We envisage that the designed hydrogels can be further advanced by employing other cargo molecules or supramolecular chemistries, which would create emerging, autonomous materials suitable for bioengineered scaffolds or coating layers that are implantable and highly sensitive to physiological signals.

This paper demonstrates a macromolecular design for deep eutectic solvent (DES)-based polymer thermosets that are adhesive but removable on demand by depolymerization. For the design of a DES, a novel self-immolative polymerizable molecule capable of donating hydrogen bonds has been synthesized to form a room-temperature eutectic mixture when combined with another olefinic hydrogen bond acceptor. The physical properties of the liquid mixture have been characterized, and the mixture has been confirmed to be suitable for the formation of easily processable, resilient, transparent thermosets through click addition polymerization. The materials not only degrade on a molecular level as designed but also show interfacial adhesion onto various substrates, yielding a debondable polymer adhesive. The adhesive strength, which is comparable to that of commercial glue, decreases significantly in response to trace amounts of fluoride under benign conditions. As an example, after exposure to 0.01 M CsF, the bonded glass substrates easily separated within 16 h at room temperature. Similarly, the energy-efficient delamination of mixed composites was also achieved. We envisage that our design concept would benefit the development of functional polymeric materials that facilitate end-of-use processes.