Mendable properties of Diels Alder thermosets: The influence of backbone flexibility and crosslinking density

A family of thermosetting epoxy resins has been prepared and characterized, containing a pair of Diels-Alder (D-A) adducts in the epoxy precursor backbone. The D-A adducts can be reversibly cleaved and reformed [1] under the appropriate thermal conditions, and this feature has been exploited to produce intrinsically self repairing materials since the pioneering work of Wudl and coworkers in the 2002 [2]. The present work has been focused to investigate the effects of different structural features, such as average number of crosslinking functionality and molecular flexibility of epoxy precursors, on the efficiency of healing process to recover the pristine material properties after mechanical damage. High crosslinking density and molecular stiffness improve mechanical performances such as elastic modulus and glass transition temperature, but on the other hand they hinder the capability of self healing. Therefore, this paper aims to elucidate the insights of self-healing phenomena and relate them to molecular structure of thermosetting precursors.