Development and Characterization of Thermoreversibly Cross-Linking Gels

Thermoreversibly cross-linking gels in which cross-links are based on the Diels-Alder reaction of pendant furans and multimaleimides have been prepared. At room temperature, these materials are gels; however, at 90°C the cross-links break apart completely and the system is effectively a solution. The thermoreversible reaction between furans and maleimides favors the product below 60°C and the reactants above 90°C. Between 60 and 90°C equilibria exist in relative concentrations of the products and reactants. Since the type of system reported has temperature-dependent cross-link densities, the relationship between temperature and mechanical properties will deviate significantly from traditional viscoelastic behavior. Preliminary work in characterizing the reaction kinetics of a reversibly cross-linking system and relating mechanical properties to the Diels-Alder reaction will be presented. Such studies are necessary to optimize the healing ability of Diels-Alder-based systems and also contribute to the understanding of networks containing equilibrium controlled cross-links.