Metal catalyzed polymerization of cyclic olefins

We have been interested in polymerization of cyclic olefins using transition metal catalysts. Two important polymerization mechanisms have been studied: ring opening metathesis polymerization (ROMP) and coordination insertion polymerization. Various kinds of transition metal complex are known to catalyze ROMP. Among those transition metal complexes, ruthenium has a great advantage of decreased oxophilicity. The lower oxophilic nature of ruthenium allows polymerization of functionalized monomer and utilization of alcohol/water as reaction medium. Several examples of the polymerization of functionalized monomers are known; however, very few examples of the polymerization in water are known. In addition, ROMP does not involve extra reagents and production of by-products. From a green chemistry standpoint, the utilization of water as solvent and clean reaction has a significance. We have reported the investigation of the ROMP of oxo-functionalized cyclic olefins in water using a ruthenium salt (Chapter 2). The polynorboraene from the coordination-insertion polymerization has great features as engineering plastics, and because of its properties many research projects of the coordination polymerization of norbornene have been done, whereas few examples of polymerization studies of other cyclic olefin have been reported. Among these cyclic olefins, cyclobutene derivatives have never been reported because of side reactions, the facile pericyclic ring opening reaction of cyclobutene during polymerization, and ROMP. This is the first report that cyclobutene derivatives have been polymerized without such side reactions to afford high-molecular-weight addition polymer (Chapter 3).