Natural materials often posessess sophisticated hierarchical structures that have evolved to perform a specific function with unparalleled efficacy. In contrast, synthetic soft materials lag far behind in their complexity and associated functionality. To broaden and/or improve the utility of polymeric (soft) materials in emergent technologies necessitates new chemical fabrication strategies that provide spatiotemporal control over the resultant properties. This presentaton will focus on the ZAP Group’s recent efforts in utilizing selective metathesis to spatially dictate the stereochemistry of a polyolefin, and in-turn it’s solid-state packing and concomittant mechanical behavior. Specifically, stereoctronlled ring-opening metathesis polymerization (ROMP) of an inexpensive monomer, cis-cyclooctene, was developed to provide either trans-polyoctenamer rubber (TOR) or cis-polyoctenamer rubber (COR) depending on the conditions. In the presence of visible light, the formation of TOR outcompetes that of COR, while in the absence of light COR is formed. In analogy to butter and oil, TOR is able to order and crystallize, while COR is not, providing more “solid-like” and “liquid-like” properties, respectively. The utility of light enabled patterning of the strong and stiff semicrystalline TOR, surrounded by soft and elastic COR, granting access to multimaterial films with tailorable mechanical properties and potential utility in soft robotics and flexible electronics.

Selective metathesis to pattern polymer crystallinity

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