Presentation description

Thermoset polymers undergo an irreversible chemical change during curing, resulting in lightweight, rigid materials ideal for aerospace and transportation industries. Traditional thermoset manufacturing methods require long cure times at high temperatures in pressurized ovens, making the process energetically unfavorable. Frontal Ring Opening Metathesis Polymerization (FROMP) is an energy-efficient alternative that only requires an initial thermo or photo stimulus to trigger a ring-opening reaction that provides enough exothermic heat to sustain a self-propagating reaction front. This ring-opening occurs at the double bond of olefins and is often catalyzed by ruthenium-based catalysts. While Ru catalysts are robust and well-established for FROMP, underdeveloped Schrock-type Mo catalysts can be more reactive and selective towards desired regio- and stereochemical reactions. To expand catalytic options for FROMP, we aim to optimize the use of Mo catalysts for polymerization of dicyclopentadiene (DCPD) and ethylidene-norbornene (ENB) monomers. Conformational searches and DFT-level energy calculations were used to identify two thermodynamically favorable Mo catalysts. However, these catalysts initiated rapid polymerization of DCPD and ENB, preventing control over reaction rate and properties such as pot life. To address this challenge, Fürstner’s approach was adapted to control the rate of polymerization, wherein an N,N ligand is used as a chemical inhibitor to form an inactive Mo complex. By addition of a Lewis acid, the N,N ligand can disassociate from the Mo complex, reforming the catalytically active Mo species. Thus far, various N,N ligands and Lewis acids have been evaluated, with the top-performing N,N ligand containing a decyl ester chain on a bipyridine. Future work for this project includes using data science tools to generate a chemical space map of ~3000 N,N ligand structures to provide strategic access to diverse experimental ligand selection.