Well‐healed: Polymers cross‐linked with trithiocarbonate (TTC) units were prepared by a RAFT polymerization. The repeatable self‐healing systems or macroscopic fusions were accomplished by UV irradiation of the cross‐linked polymer in solution and in the bulk state. The macroscopic fusion of completely separated parts was successful (see pictures, BA=n‐butyl acrylate).

Self-healing polymeric materials with branched architectures and reversible cross-linking functionalities at the periphery of branches were synthesized by atom transfer radical polymerization (ATRP). Poly(n-butyl acrylate) grafted star polymers were prepared by chain extension ATRP from cross-linked cores comprised of poly(ethylene glycol diacrylate). These polymers were further used as macroinitiators for the consecutive chain extension ATRP of bis(2-methacryloyloxyethyl disulfide) (DSDMA), in which way disulfide reversible cross-links (SS) were introduced at the branch peripheries. The SS cross-linked polymers were then cleaved under reducing conditions to form thiol (SH)-functionalized soluble star polymers. The SH-functionalized star polymer solutions were deposited on silicon wafer substrates and converted to insoluble SS re-cross-linked films via oxidation. The self-healing of prepared polymer films was studied by continuous atomic force microscopy (AFM) imaging of cuts micromachined with the AFM tip and by optical microscopy. The re-cross-linked star polymer (X3) showed a rapid spontaneous self-healing behavior, with the extent of healing dependent on the initial film thickness and the width of the cut. The self-healing behavior observed for this sample was attributed to the regeneration of SS bonds via thiol–disulfide exchange reactions. This study demonstrated the suitability of grafted multiarm polymer architectures as building blocks of self-healing polymeric materials and pointed to the importance of low intrinsic viscosity of material and high accessibility of functional groups responsible for healing.

Dimethacrylate trithiocarbonate was synthesized and used as a dynamic covalent cross-linker to prepare PMMA and PSt gels via radical polymerization. The swelling properties of the PMMA gels were studied and showed that in the presence of radicals the gels reorganize to accommodate forces generated by the swelling processes. This reshuffling of the cross-link network yields an increase in the swelling ratio (up to 300% increase) of the PMMA gels. Two different radical generators, a thermal initiator and a CuI/L complex, were successfully used to trigger the reorganization of the gels. To illustrate the broad utility of the procedure, three discrete pieces of gels were fused into one single piece to demonstrate that dynamic covalent cross-linkers can be used to prepare materials that can be reprocessed and/or undergo self-repair.