Frontal ring-opening metathesis polymerization (FROMP) is an appealing process for the rapid fabrication of structural polymers. The use of alkyl phosphites in controlling the activity of metathesis polymerization has introduced a myriad of new opportunities for FROMP in manufacturing polymeric materials. Observations of sub-stoichiometric inhibitor having great effect on pot-life and gelation at room temperature prompted a more detailed mechanistic study. Here, we investigate the kinetics and catalyst-ligand interactions of alkyl phosphite inhibited FROMP. Key ruthenium-phosphite species were synthesized and evaluated alongside traditional Grubbs’ metathesis initiators. Ligand dissociation kinetics, catalyst initiation rates, polymerization kinetics and ligand-catalyst equilibria were studied by solution NMR spectroscopy. The mechanistic probes and obtained rate constants are consistent with a competitive inhibition mechanism where phosphite preferentially binds to the propagating Ru-polymer chain with respect to the alkene monomer, thus lengthening working time and pot-life.

Mechanistic insight into alkyl phosphite inhibited frontal ring-opening metathesis polymerization

255th National Meeting (2018)

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