Click-based dual-curing thermosets and their applications

Abstract

Dual curing is the methodology for obtaining thermosets by combining two different and compatible polymerization reactions, taking place sequentially or simultaneously. Sequential dual-curing processing enables the preparation of handleable materials after a first stage of curing that, upon application of a second stimulus, further cross-link to achieve the ultimate properties. Controlled curing sequences can be achieved by means of using latent catalysts that are activated upon irradiation or temperature, or else by thermal control of the reaction kinetics. Many possible combinations of reactions are possible, especially those including click-type polymerization reactions, which are especially suited because of their efficiency, selectivity, and orthogonality. Careful choice of the polymerization reactions, monomer composition, and structure makes it possible to obtain intermediate materials with well-defined rheological, thermal, and mechanical properties, ranging from those of viscoelastic liquids to lightly cross-linked rubbers or glassy cross-linked networks. After the second curing stage, the materials complete the cross-linking process and reach the ultimate properties required for the end use of the material. This unique combination of features represents significant advantages in terms of processing flexibility, facilitating manufacturing, and assembly in comparison with curing systems based on a single polymerization reaction and opens new application perspectives in diverse areas such as photopatterning, holography, shape-memory devices, or microfluidics.