One of the most prominent features of macromolecules, which governs many material properties, is the architectural precision of the microstructure. The more defined the polymer, the better we can understand how regioregularity and tacticity ultimately define material properties. Over a decade ago, the Hillymer Group showed that bulky allylic substituents placed on <i>cis</i>-cyclooctene monomers could dictate a preferential distal monomer insertion on typical Ru-based (Grubbs-type) catalysts, leading to highly regio-regular and precise materials. Over the last several years, our team has investigated this preferential distal insertion from allylic-substituted cyclopentene derivatives and have revealed an unexplored landscape of materials that feature a five-carbon branch periodicity and a high degree of microstructural control. While cyclopentene monomers present their own challenges, which will be discussed, we recently took the regio-regular materials one step further through utilization of enantiopure cyclopentene monomers. Following ROMP and hydrogenation of the backbone olefins, the resulting materials are the first to feature isotactic branch periodicities at every fifth carbon along a polyethylene backbone. We designed the isotactic branches to be alcohol groups and then compared thermal properties, such as glass transition and melting temperatures, to atactic counterparts. It was discovered that the isotactic structure leads to some of the highest crystalline melting temperatures to date. Insights on these discoveries and the resulting crystal structures will be discussed.

Utilizing ROMP to create regio-regular and isotactic materials outside typical polyolefins

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