Flexible Photothermal Materials with Controllable Accurate Healing and Reversible Adhesive Abilities

Abstract

As one of the first studied photothermal agents, eumelanin is often used for photothermal materials based on its broadband light absorption ability, biocompatibility, and cheap availability. However, it is still a challenge to conduct in-depth development of the photothermal effect of eumelanin in flexible polymeric composites due to its dispersion problem. Here, we report light-controlled healable and reversible adhesive elastomers using polar liquid cross-linkers to assist eumelanin dispersion into carboxylic styrene butadiene rubber (XSBR). The uniformly dispersed eumelanin and the coordination between Zn2+ and eumelanin bring the elastomer a satisfactory photothermal conversion efficiency (80%), even if only 1 phr eumelanin is added. Under near-infrared (NIR) laser irradiation of 0.55 W cm–2, the temperature of the elastomer with 1 phr eumelanin sharply increases from room temperature to 120 and ∼190 °C (the maximum temperature) in 20 and 90 s, respectively. Benefiting from the efficient photothermal conversion ability and transesterification, the elastomer shows excellent NIR light-controlled healing ability, and its healing efficiency can reach 94%. Based on noncovalent interactions (mainly hydrogen bonds), the elastomer shows temperature-dependent reversible adhesive behavior. The adhesion strength of the elastomer can be adjusted by changing the temperature or irradiating light, thus facilitating the disassembly and reuse of the elastomers. Thanks to these advantages, the obtained elastomers have potential applications in harvesting sunlight for electricity generation and also provide insights into the development of sustainable reversible adhesive materials.