Photoredox-Initiated Frontal Ring-Opening Metathesis Polymerization

Herein, we report the development of a photoredox-initiated frontal ring-opening metathesis polymerization (FROMP) chemical system. We found that a ruthenium-based, bis-N-heterocyclic carbene metathesis precatalyst was activated with 9-mesityl-10-phenylacridindium tetrafluoroborate, copper(II) triflate, and a 455 nm light source. This chemistry was used to initiate the FROMP of dicyclopentadiene; once initiated, the heat released from the polymerization sustained a well-controlled reaction front. Variation in copper or metathesis precatalyst loading yielded front speeds ranging from 0.15 to 0.43 mm s^-1 and front temperatures ranging from 140 to 205 °C. While the glass transition temperatures of the resultant polymers are lower than those derived with Grubbs' second-generation catalyst, this chemical system provides extended pot life.