Surface Passivating Dynamic Imine Networks with Enhanced Water Resistance

Dynamic covalent bond-based polymers, such as covalent adaptable networks (CANs) have been proposed to overcome the limitations of permanently crosslinked networks through reversible bond exchange. In particular, dynamic imine bond network is commonly used due to catalyst-free bond formation and rapid bond exchange from Schiff-base reaction. However, imine bond is highly susceptible to hydrolysis upon water exposure, which leads to undesired bond cleavage and progressive reduction in crosslink density. To address this issue, we introduce a paraffin embedded dynamic imine bond-based PDMS (PW/DI-PDMS) by incorporating hydrophobic paraffin wax as a water shielding component. The paraffin spontaneously migrates to the surface and forms a hydrophobic crystalline layer that suppresses water penetration and protects the imine bond from hydrolytic degradation. After imine bond crosslinking, paraffin is retained in an amorphous state due to spatial confinement within the PDMS network, allowing internal wax to migrate toward the surface. Internal wax can also be secreted out and reform a passivation layer even after the outermost wax has been removed. This water-resistant, self-repairable PW/DI-PDMS continuously forms a protective layer and maintains network stability, highlighting its potential for applications that require prolonged exposure to water.