Structure–Property Relationships of Self-Healing Polymer Networks Based on Reversible Diels–Alder Chemistry
Seppe Terryn, Joost Brancart, Ellen Roels, Robrecht René Verhelle, Ali Safaei, Audrey Cuvellier, Bram Vanderborght, Guy Van Assche
Abstract
Recently, the Diels–Alder reaction between furan and maleimide functional groups has been exploited in dynamic reversible covalent networks, introducing a healing ability and reprocessing in various applications. Both applications and (re)processing techniques impose specific requirements, which can be met by the large tunability of the material properties of Diels–Alder-based networks. The extensive set of structure–property relations presented in this paper allows for designing Diels–Alder networks meeting a broad range of material properties. Three major network design parameters are defined that influence these properties: the Diels–Alder concentration, the degree of functionality of the reactive maleimide and furan groups on the monomers, and the stoichiometric ratio between these reactive groups. Their individual influences on the kinetics and the thermomechanical, rheological, and healing properties were investigated via tensile testing, differential scanning calorimetry, dynamic mechanical analysis, and dynamic rheometry. By tuning the design parameters independently, mechanical properties can be matched with requirements imposed by applications by changing the Diels–Alder concentration, while healing speeds can be further altered by the stoichiometric ratio between maleimide and furan groups. In addition, the temperature of gelation, crucial for processing, can be tuned by means of the functionality parameter, meeting requirements imposed by manufacturing techniques.