Disulfide Bond Accelerated Transesterification in Poly(β-hydrazide disulfide esters) toward Fast Network Rearrangements.

The development of catalyst-free ester-based covalent adaptable networks (CANs) provides a new approach to achieve milder reaction conditions to reprocess thermoset resins. Despite recent advances, however, accelerating network rearrangements requires the introduction of hydroxyl groups into the network. In this study, disulfide bonds are introduced into the CANs to add new kinetically facile pathways to accelerate network rearrangement. Kinetic experiments using small molecule models of the CANs show that the presence of the disulfide bonds can accelerate transesterification. These insights are applied to synthesize new kinds of poly(β-hydrazide disulfide esters) (PSHEs) using thioctic acyl hydrazine (TAH) as a precursor for ring-opening polymerization with the hydroxyl-free multifunctional acrylates. The PSHE CANs have lower relaxation times (505-652 s) than the polymer containing only β-hydrazide esters (2903 s). The ring-opening polymerization of TAH improves the crosslinking density, heating resistance deformation temperature, and UV shielding performance of the PSHEs. Thus, this work provides a practical strategy to reduce the reprocessing temperatures of CANs.