Orthogonal dynamic covalent boroxine-crosslinked poly(disulfide) networks for chemically recyclable encryption materials

Replacing the "inert" chemical bonds in traditional materials with dynamic bonds brings opportunities in designing renewable materials that repair, reprocess and recycle. Despite the many efforts made in covalent adaptable networks by elaborating a single type of dynamic covalent chemistry, the fabrication of double dynamic covalent polymeric networks, especially using simple small-molecule building blocks, still remains challenging. Here we report the solvent-free construction of a thermosetting material by combining 1,2-dithiolane-based reversible polymerization and dynamic covalent boroxine chemistry as crosslinkers. The resulting materials exhibit tunable mechanical properties, mechanical reprocessability, shape memory ability and closed-loop chemical recyclability. Quantitative kinetic analysis reveals the temperature-dependent apparent activation energy for the bond exchange of the resulting network as a result of the simultaneous integration of the two dynamic covalent bonds. Meanwhile, the boroxine units also act as a luminescent center to enable an emissive "organic glass" that can be used as a dual encryption material taking advantage of the reprogrammable shape-memory behavior of the dynamic network. Benefitting from the simple design, tunable variables and multi-functions, we envision that this double dynamic chemistry offers a robust scaffold and great chemical spaces for the design of dynamic polymeric materials.