Thermally Healable and Reprocessable Bis(hindered amino)disulfide-Cross-Linked Polymethacrylate Networks

A facile approach to polymethacrylate networks that contain thermally exchangeable bis(2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS) cross-linkers is reported, and the easily inducible healability and reprocessability of the obtained networks are discussed. The free radical polymerization of BiTEMPS cross-linkers and hexyl methacrylate (HMA) monomers afforded insoluble and colorless networks of poly(hexyl methacrylate) (PHMA) films, whose structures were characterized after de-cross-linking via thermal BiTEMPS exchange reactions with added low-molecular-weight BiTEMPS. Swelling experiments and stress-relaxation measurements at elevated temperatures revealed the contribution of BiTEMPS as a polymer chain exchanger both in the gels and in the bulk. The BiTEMPS-cross-linked PHMA networks showed damage healability and repeatable reprocessability in the bulk by simple hot pressing at 120 °C under mild pressure (∼70 kPa). These results should grant facile access to various vinyl polymer networks with on-demand malleability.