Mechanically adaptive conducting polymers

We report the development of mechanically adaptive conducting polymers—a new class of materials with toughness that dynamically scales with the rate of deformation. For example, as the rate of stretching increased from 2.5 to 10000 %/min, the ultimate elongation of this material becomes 7 times higher and the toughness increases by over 100 folds. This unusual rate property is achieved by creating dynamic bonds of different strengths within the polymer microstructure. The stronger dynamic bonds maintain material integrity, whereas the clusters of weaker dynamic bonds serve as a sacrificial network and dissociate at a rate that directly scales with the loading rate. In-situ small and wide angle X-ray scattering (SAXS and WAXS, respectively) studies reveal that when the rate of loading exceeds a critical strain rate, deformation through the sacrificial network becomes more favorable than the classical viscoelastic pathway, which led the polymer to defy viscoelasticity and exhibit mechanical adaptiveness. This mechanism can potentially lead to soft thermoplastic materials that are more durable under high impact conditions, increasing the reliability and lifetime of the resulting devices.