Timothy C. Mauldin

Self-healing Polymers and Composites

Abstract Inspired by the unique and efficient wound healing processes in biological systems, several approaches to develop synthetic polymers that can repair themselves with complete, or nearly complete, autonomy have recently been developed. This review aims to survey the rapidly expanding field of self-healing polymers by reviewing the major successful autonomic repairing mechanisms developed over the last decade. Additionally, we discuss several issues related to transferring these self-healing technologies from the laboratory to real applications, such as virgin polymer property changes as a result of the added healing functionality, healing in thin films v. bulk polymers, and healing in the presence of structural reinforcements.

Enhanced bulk catalyst dissolution for self-healing materials

A model was developed to aid in the selection of healing monomers that can rapidly dissolve catalysts in self-healing materials. Predictions are made regarding dissolution rates of Grubbs catalyst in a small library of ring-opening metathesis polymerization (ROMP)-active norbornenyl-based healing monomers. The Grubbs catalyst and the healing monomers were experimentally assigned sets of Hansen parameters, and it was observed that healing monomers and blends of monomers with parameters similar to the catalyst were able to rapidly dissolve the catalyst. The model is limited in its ability to predict dissolution trends of healing monomers with substantially different viscosities.

Modified rheokinetic technique to enhance the understanding of microcapsule-based self-healing polymers.

A modified rheokinetic technique was developed to monitor the polymerization of healing monomers in a microcapsule-based, self-healing mimicking environment. Using this modified technique, monomers active toward ring-opening metathesis polymerization (ROMP) were either identified or disregarded as candidates for incorporation in self-healing polymers. The effect of initiator loading on the quality and speed of healing was also studied. It was observed that self-healing polymers have upper and lower temperature limits between which the healing mechanism performs at optimal levels. Also, a study of the quality of healing cracks of different thicknesses was performed, and it was discovered that above a critical crack thickness value, the quality of self-healing diminishes substantially; reasons for this phenomenon are discussed in detail.