(4s) Development and Characterization of Remendable Polymer Composites Using the Diels-Alder Reaction

Materials that can repair cracks and recover from mechanical failure are desirable. Because remendable materials both repair and prevent the propagation of cracks on the micro scale, they offer the potential for increased durability, safety, and cost efficiency for many applications. The focus of my work is to understand the kinetic and thermodynamic parameters that control thermoreversible Diels-Alder bond formation in different types of healing polymeric systems. 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 bonds. I have developed three healing systems for epoxy-amine thermosets based on the thermoreversible Diels-Alder reaction of furan and maleimide. In one, crack healing of a traditional epoxy-amine thermoset is induced by thermally reversible cross-linking of a secondary phase. In another, a furan-functionalized epoxy-amine thermoset can be healed with a bismaleimide solution at room temperature and minimal pressure and significant load recovery is possible multiple times in a given location. The third system allows for interfacial healing of glass fiber-reinforced epoxy-amine composites via compatible functionalization of glass fibers and the polymer network. Although the Diels-Alder reaction was discovered almost 70 years ago, there has not been an exhaustive study of reaction kinetics and thermodynamic parameters for furan and maleimide. Kinetic parameters have been determined for a number of model compound systems. 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 as well.