An Ion?Pairing Approach to Stereoselective Metal?Free Ring?Opening Metathesis Polymerization

Stereochemistry can have a profound impact on polymer and materials properties. Unfortunately, straightforward methods for realizing high levels of stereocontrolled polymerizations are often challenging to achieve. In departure from traditional metal-mediated ring-opening metathesis polymerization (ROMP), we discovered remarkably simple method controlling alkene stereochemistry in photoredox mediated metal-free ROMP. Ion-pairing, initiator sterics, solvation effects each had the polynorbornene (PNB). Simple modifications reaction conditions produced PNB with trans content 25 >98 %. High cis was obtained relatively larger counterions, toluene as solvent, low temperatures (?78 °C), initiators Charton values. Conversely, smaller dichloromethane enol ethers higher values enabled production content. Data combined experimental computational investigation consistent stereocontrolling step radical cationic mechanism proceeding under thermodynamic control.