Preparation of functionalized diene-elastomers upon top-down pyrolysis of their vulcanizates via dynamic covalent polymerization

Abstract

Decorating diene rubbers with functional handles through copolymerization with polar monomers or post-modification of the chain backbone still struggles with some stubborn problems, including the dependence on specific catalytic systems, inescapable side reactions and poor tunability. Herein, we pioneer a brand-new methodology to rationally design functionalized diene rubbers with tunable chain structures. More specifically, by adopting the disulfide/polysulfide linkages in vulcanizates as reactive substrates, these linkages can be cleaved into active sulfur radicals upon solvothermal pyrolysis, which not only enable network disintegration but initiate the direct insertion of functional vinyl monomers into the rubber skeleton through a dynamic covalent polymerization mechanism. Accordingly, the local polarity of the functionalized chain segments increases, which reduces compatibility with the pristine components and hence facilitates the high-yield separation (∼98 wt%) of these functionalized rubbers from the network architecture. The chain structure of the obtained functionalized rubbers can be facilely tuned by regulating the pyrolysis conditions (time and temperature) and monomer content. More importantly, it is demonstrated that this methodology is versatile for obtaining functionalized rubbers with desired handles from various vulcanizates and vinyl monomers. Therefore, we envision that the present methodology will have important scientific and economic significance, since it exploits a feasible alternative for custom-made functionalized rubbers that will have broad application prospects, such as functional coupling agents, and self-healing and shape memory materials.