(164ac) The Epoxidized Polybutadiene Vitrimers: Preparation and Properties

Traditional covalently crosslinked diene rubber having excellent thermal-mechanical properties and solvent resistance but are incapable of recycling via universal molding or injecting. As a new class of covalently crosslinked polymer networks, vitrimers can be topologically rearranged with the associative exchange mechanism to make them fully malleable without impairing the network connection. Introducing the concept of vitrimers into crosslinked networks for the recycling of rubbers is currently an attractive research topic. However, designing tailored rubber vitrimers still remains a challenge. Herein, a series of epoxidized polybutadiene vitrimers are prepared via ring-opening esterification reactions between epoxy groups and disulfide-containing dicarboxylic acids, and the relation between networks and their mechanical and relaxation properties are investigated. It has been found that the vitrimer with a higher crosslinking density requires a higher energy for altering the network topology. The increasing crosslinking density can improve Young’s modulus and tensile strength. The influence of side-group effects on their relaxation properties shows that the increase of the number of epoxy groups on the polybutadiene chain can increase the chance in effective exchange of disulfide units. In addition, the results show a good recycling ability due to the thermo-activated disulfide exchange, and the balance between relaxation and creep resistance can be achieved via simple variation of crosslinking density.