Trends in Ring-Opening Metathesis Polymerization

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Abstract
Several transition metal alkylidene complexes are first discussed as catalysts for the ring-opening metathesis reaction. A new ruthenium catalyst with a slightly enhanced reaction rate is introduced. The stereochemistry and kinetics of the catalysts are investigated with different norbornene derivatives. Then it is shown that MgCl2 alone is a good heterogeneous catalyst for the ring-opening polymerization (ROMP) of norbornene compounds. This is the first catalyst which does not need activation by a transition metal compound or another organometallic cocatalyst. Applications of the ROMP reaction for the synthesis of polymer specialities covering conjugated liquid crystals and optically active polymers are shown. Poly(cyclopentadienylene vinylene) and sidechain liquid crystal polymers are discussed in more detail. Finally, the synthesis of liquid crystalline elastomers by incorporation of bifunctional monomers during the ROMP reaction is described. It is shown that this kind of polymer can be used for the fabrication of optically anisotropic materials.