465379 Novel Stimuli-Triggered Self-Healing and Strengthening Polymers
Here, we report a new class of photo-responsive polymer networks in which a dynamic bond is incorporated into the crosslinks of the network and undergoes a light-triggered, secondary polymerization which increases the modulus by two orders of magnitude while strengthening the network by over 100% . Unlike traditional two-stage polymerization systems, in which the secondary polymerization is triggered by a leachable photoinitiator [6, 7], we incorporated a dynamic bond capable of initiating polymerization into the network backbone itself. By imparting functionality directly into the network architecture, our material is capable of initiating polymerization via the dissociation of its own crosslinks to become stronger in response to light. Specifically, a labile carbon-dithiocarbamate bond (or iniferter) was incorporated into the network backbone, which triggers a light-initiated, free-radical polymerization that increases the modulus by several orders of magnitude and approximately doubles the strength. The final modulus can be tuned a prioriby modifying the concentration of the polymerizable group in the formulation. By adjusting the concentration, the material properties post-cure can be tailored to meet a wide range of specifications. The dynamic polymer network is readily transferrable to several applications. Specifically, we have demonstrated three properties: 1) photo-induced healing, reforming, and strengthening of a specimen after it has been severed, 2) spatial confinement of bulk property changes via photopatterning and 3) photo-curing the film into any particular 3D configuration.
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