Recyclable crosslinked elastomer based on dynamic dithioacetals

Recent progress in introducing elegant dynamic covalent bonds into covalently crosslinked networks enabled the trade-offs between chemical crosslinking and recycling. Thus far, continuous efforts are made to exploit new dynamic chemistries to address the constrains of intricate preparation procedures and need of catalyst additives in creating dynamic covalent networks. In this work, we report an industrially feasible process to prepare catalyst-free malleable elastomers by engineering dithioacetals as the dynamic motifs into a commercial diene rubber. Specifically, a dithioacetal-containing diacid (BTA) is synthesized and used as a novel crosslinker for epoxidized natural rubber (ENR), by which dynamic dithioacetals are introduced into the elastomeric networks. Small molecule model study shows that dithioacetal exchange can be conducted at elevated temperature without catalyst. In the BTA crosslinked ENR, the thermoactivated dithioacetal exchange reactions can alter its network topologies in an associative pathway and confer it with remarkable reprocessability. The mechanical properties and relaxation rate of the networks can be readily manipulated by varying the dithioacetal concentration.