Room-temperature versus heating-mediated healing of a Diels-Alder crosslinked polymer network

The healing behavior of a dynamically reversible covalent polymer network with a T-g of 3 degrees C, based on the reversible Diels-Alder (DA) cycloaddition between furan and maleimide moieties is reported, for both room-temperature and heating-mediated healing. In previous work the dynamic character of the DA cycloaddition reaction in a polymer network was studied, those findings are used to understand its healing ability. The recovery of mechanical properties by intrinsic healing is studied by Dynamic Mechanical Analysis, quantifying the loss in properties due to incurred damage and assessing their recovery with respect to the original material. The DA cycloadduct bonds in the network can be mechanically activated to autonomously heal damage at room temperature if the damage surfaces remain activated. If the damage surfaces are not brought in contact fast enough they reestablish equilibrium (aging) and lose their autonomous healing potential. In the latter case, only heating-mediated healing can occur, reactivating the healing ability. Controlled damage formation and subsequent sealing of the damage of network coatings is monitored by Atomic Force Microscopy and optical microscopy. The repeatability for both mechanical activation, studied by tensile testing, and thermal cycling, studied by Differential Scanning Calorimetry, is reported.