Abstract: The present invention provides novel polyolefin compositions having variable hardness and/or toughness properties. The polyolefin compositions include: a polyolefin prepared by the metathesis of an olefin monomer using a ruthenium or osmium carbene catalyst; and one or more hardness and/or toughness modulators. The polyolefin is preferably poly(dicyclopentadiene), or poly-DCPD. Also provided are articles of manufacture, such as molded parts, produced from the polyolefin compositions. The disclosed compositions are useful in marine, recreational and sports products.

Abstract: Methods for synthesizing polyDCPD via ROMP of low grade DCPD starting materials using Ruthenium or Osmium carbene complex catalyst. Transparent or translucent polyDCPD materials. The Ruthenium or Osmium carbene complex catalysts having the formula ##STR1## where M may be Os or Ru; R and R.sup.1 may be the same or different and may be hydrogen or a substituent group including C.sub.2 -C.sub.20 alkenyl, C.sub.2 -C.sub.20 alkynyl, C.sub.1 -C.sub.20 alkyl, aryl, C.sub.1 -C.sub.20 carboxylate, C.sub.1 -C.sub.20 alkoxy, C.sub.2 -C.sub.20 alkenyloxy, C.sub.2 -C.sub.20 alkynyloxy, aryloxy, C.sub.2 -C.sub.20 alkoxycarbonyl, C.sub.1 -C.sub.20 alkylthio, C.sub.1 -C.sub.20 alkylsulfonyl and C.sub.1 -C.sub.20 alkylsulfinyl; X and X.sup.1 may be the same or different and may be any anionic ligand; and L and L.sup.1 may be the same or different and may be neutral electron donor. The low grade DCPD starting materials containing less than about 97% by weight of DCPD monomers.