Leveraging Mechanistic Insights into Stereoretentive ROMP for Precision Synthesis of Poly(p-phenylene vinylene)s

Poly(p-phenylene vinylene) (PPV) is an important class of conjugated polymers whose properties are largely dictated by structural parameters such as backbone regioregularity, defect content, alkene geometry, side-chain structure, and the sequence of repeat units. Despite decades of development and applications spanning optoelectronic devices to biomedical imaging, a controlled, defect-free polymerization method that affords predictable command over all structural attributes of PPVs has remained elusive. We report herein the synthesis of a variety of regioregular and stereodefined PPVs through stereoretentive ring-opening metathesis polymerization (ROMP) of electronically and sterically diverse [2.2]paracyclophane-1,9-dienes (PCDs). Computational studies were combined with experimental findings to uncover structural design principles underlying controlled propagation as well as regio- and stereoselectivity. These findings were harnessed to access well-defined gradient and one-shot block PPV copolymers, as well as unprecedented stereoblocks with cis and trans block geometries through in situ photoisomerization. The influence of monomer composition and alkene geometry on the optical properties of the synthesized PPVs was also investigated. The exceptional structural control achieved through stereoretentive ROMP of PCDs establishes a unique platform for the precise synthesis of PPVs with tailored properties.