A feasible and versatile strategy to endow rubbers with self-healing based on reversible non-covalent interactions: A concept of self-healing masterbatch

To achieve self-healing for commercial rubbers, the current mainstream strategy is to equip rubber molecules with essential functional groups by chemical modifications. However, different structure of rubber molecules determines a disparate optimal self-healing mechanism, which turns out a consequent complex and multifarious chemical modifications for them. In other words, the same modification method cannot be applied to various rubbers, which is partly a limitation on the preparation of self-healing rubbers. Herein, we propose a concept of self-healing masterbatch which can effectively endow rubber matrix with self-healing ability via a facile processing method. We design this rubber masterbatch equipped with a mass of carboxyl groups by the grafting reaction between natural rubber and 2-methacrylic acid. Then the rubber masterbatch can be mixed with rubber matrix and simultaneously ZnO must be added to introduce Zn2+ via its neutralization reaction with the masterbatch. After a controlled peroxide-induced vulcanization, the chains of masterbatch are grafted onto the chains of rubber matrix and then a reversible Zn2+ crosslinking network is generated. Based on above method, natural rubber, styrene butadiene rubber and cis-polybutadiene rubber successfully earn considerable self-healing ability, showing a self-healing efficiency of >90%. Furthermore, based on the reversible non-covalent interactions between the carboxyl groups of the self-healing masterbatch and inorganic substrates, the self-healing masterbatch can recover its adhesion and reuse to bond the cements together, showing a “dynamic reversible adhesion”. We hope this concept of self-healing masterbatch could open up a feasible and versatile avenue to prepare self-healing rubbers based on reversible non-covalent interactions.