Olefin metathesis polymerizations have enabled the synthesis of a large variety of polymers such as polyalkenamers or poly(arylene vinylene)s. While numerous studies have shown that the stereochemistry of the alkenes in the polymer backbone has a notable impact on the physical properties of the polymer, the synthesis of stereodefined polymers via olefin metathesis remains a great challenge. Most metathesis catalysts operate under thermodynamic control, which generally favors E (trans) linkages. Therefore, the properties of polymers with high-cis content are generally underexplored due to a scarcity of synthetic methods to access these structures. Within these polymers, poly(p-phenylene vinylene)s (PPVs), consisting of alternating alkenes and phenyl groups in conjugation, is of special interest. Indeed, the cis/trans configuration of the olefins on the PPV backbone significantly affects its physical properties including optical behavior and solubility. In addition, one-way photoisomerization can readily transform olefins in the PPV backbone from the cis to the trans configuration, rendering PPVs a stimuli-responsive material. In this presentation, we will discuss a unique strategy to access all-cis PPVs with living characteristics capitalizing on the polymerization of paracyclophane diene monomers via stereoretentive ring-opening metathesis polymerization (ROMP). Investigation of the kinetics of the polymerization and its living character will be highlighted. Finally, applications to the synthesis of photoresponsive diblock copolymers will be presented with an eye towards the construction of intricate and well-defined polymeric architectures containing all-cis PPVs as stimuli-responsive materials.

Accessing olefin containing polymers with high-cis content via stereoretentive olefin metathesis polymerization

ACS Fall 2021

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