Precise Placement of Single Monomer Units in Living Ring-Opening Metathesis Polymerization

Precise control of the location and sequence of monomers in a narrow-disperse polymer chain remains a significant challenge. Our strategy uses selective and quantitative single additions of cyclopropene (CPE) derivatives to precisely place functional moieties at desired locations along a polymer chain during the living ring-opening metathesis polymerization (ROMP) of norbornenes (NBEs). In order to completely reinitiate the chain end after single addition of a CPE, we lowered the reaction temperature and added a labile ligand. Under our optimized conditions, we demonstrated the exclusive placement of single moieties at pre-determined locations along a polynorbornene (PNBE) homo or block co-polymer while maintaining narrow MW distributions and controlled MWs. Some polymers were used to synthesize precisely controlled branched architectures. The ability to control the location and number of individual functional groups in a polymer chain opens exciting opportunities for the precise synthesis and manipulation of polymer structures, architectures, assemblies, and properties.