(558b) Self-Healing Through Mechanochemistry

Spiropyran mechanophores (mechanochemically reactive units) can impart the unique functionality of visual stress detection to polymers and have potential for use in smart materials with self-sensing capabilities. Other mechanophores may enable mechanical induced self-healing.  These mechanophores were incorporated into polyurethane and related polymers via step growth polymerization. Polyurethane, which is inherently a versatile engineering polymer, possesses an optimized balance of mechanical toughness and elasticity to allow for investigation of the kinetics of the mechanochemical response of the mechanophores in the bulk polymer. For example, the stress-induced 6-π electrocyclic ring-opening to the colored merocyanine form of the spiropyran mechanophore was quantified by measuring the change in absorbance of the polymer, while it was held at constant strain. The closing kinetics of the mechanophore was also studied by fluorescence imaging. Finally, the effects of mechanical strain on the equilibrium between the two forms are reported and discussed.