Intrinsic self-healing of polymer solid while keeping integrity and load-bearing capability

Generally, intrinsic self-healing polymers based on reversible covalent bonds scission and reconnection would lose their load bearing capability as a result of molecular cleavage during healing process. This shortcoming also results in creep deformation of the products. To solve the problem, we introduce a novel healing mechanism by using dynamically reversible C-ON bonds. Upon heating to a certain homolysis temperature, C-ON bonds in alkoxyamines moieties frequently cleave but immediately recombine. When alkoxyamines are incorporated into polymer chains, C-ON covalent bonds fission and recombination synchronously take place with very high frequency, and the equilibrium tends to the combination side. Cracked parts can thus be restored through chemical exchange reaction of alkoxyamine moieties. More importantly, because a large amount of C-ON bonds remain connection, the possible material deformation in the course of crack remending could be avoided. Here, crosslinked polystyrenes and epoxy with alkoxyamine moieties are synthesized as model polymers to prove feasibility of the above considerations. It is shown that the polymers can repeatedly self-heal cracks without deformation induced by chain scission, and provides the polymer with mechanical stability at elevated temperature as well. Moreover, the healing can be conducted within a wide temperature range when different alkoxyamines moieties are used. Molecular structures of alkoxyamines moieties, as well as thermodynamic behavior of C-ON bonds scission and recombination, etc., are studied in detail to optimize selfhealing behavior of the polymers. Full reversibility can be acquired when only one type of C-ON bond is included in the polymers. Accordingly, synthesis routes, molecular structures, thermally reversible characteristics, self-healing performance and self-healing mechanism, thermal stability and thermal-mechanical properties, etc, have been studied in detail