A new dual-curing system based on sequential thiol–epoxy click polycondensation and epoxy anionic homopolymerization was studied. Formulations of diglycidyl ether of bisphenol A and trimethylolpropane tris(3-mercaptopropionate) with 1-methylimidazole as a base catalyst and excess of epoxy groups were prepared and characterized. The curing process is sequential: fast thiol–epoxy polycondensation takes place first, followed by slower homopolymerization of excess epoxy groups. This makes it possible to define curing sequences with easy time–temperature control for both curing stages. The network build-up process during the first curing stage can be easily modelled assuming ideal polycondensation, which allows tailoring the structure and properties of the intermediate materials. The homopolymerization of the excess epoxy groups in the second curing stage results in a higher glass transition temperature (T_g) in comparison with the stoichiometric thiol–epoxy material, thus extending the application of thiol–epoxy thermosets to wider temperature ranges.

This study presents the synthesis of a novel biobased epoxy monomer derived from vanillin and cystamine, incorporating imine and disulfide exchangeable groups within its structure. A series of epoxy-based vitrimers with two simultaneous exchange relaxation processes have been produced using this monomer. These exchange mechanisms operate without the need for any catalyst. Four different amine curing agents have been employed to achieve vitrimers with glass transition temperatures around 100 °C and excellent thermal stability. Through dynamic-mechanical analyses, thermomechanical properties and vitrimeric characteristics have been investigated, revealing remarkably fast stress relaxation at relatively low temperatures without significant creep below the glass transition temperature. Leveraging the dual exchange mechanism, the chemical degradability of these vitrimers has been explored through two accessible methodologies, and the material's reformation after degradation has been demonstrated in both cases. Furthermore, the material has been mechanically recycled, maintaining almost the same properties. Finally, these materials have been used to fabricate and recycle carbon-fiber-reinforced composite material and reversible adhesives, showcasing their promising potential applications.

Supramolecular hydrogels are 3D, elastic, water-swelled materials that are held together by reversible, non-covalent interactions, such as hydrogen bonds, hydrophobic, ionic, host–guest interactions, and metal–ligand coordination. These interactions determine the hydrogels’ unique properties: mechanical strength; stretchability; injectability; ability to self-heal; shear-thinning; and sensitivity to stimuli, e.g., pH, temperature, the presence of ions, and other chemical substances. For this reason, supramolecular hydrogels have attracted considerable attention as carriers for active substance delivery systems. In this paper, we focused on the various types of non-covalent interactions. The hydrogen bonds, hydrophobic, ionic, coordination, and host–guest interactions between hydrogel components have been described. We also provided an overview of the recent studies on supramolecular hydrogel applications, such as cancer therapy, anti-inflammatory gels, antimicrobial activity, controlled gene drug delivery, and tissue engineering.