Ring-opening metathesis polymerizations with norbornene carboxylate-substituted metal oxo clusters

The clusters Ti6O4(OPr)(8)(endo,exo-OOC-Norb)(8), Zr6O4(OH)(4)(endo-OOC-Norb)(12) and Zr6O4(OH)(4)(exo-OOC-Norb)(12)(BuOH) were prepared by the reaction of 5-norbornene-2-carboxylic acid (HOOC-Norb) with Ti(OPr)(4) or Zr(OBu)(4) and were characterized by X-ray structure analyses. Ring-opening metathesis polymerization was performed with Zr6O4(OH)(4)(OOC-Norb)(12) either in the absence or in the presence of norbornene. Highly crosslinked polynorbornene was obtained in the latter reactions. The onset of thermal decomposition of the polynorbornene crosslinked by 1-5 mol% of the cluster was about 40-45 degrees higher than that of pristine polynorbornene. Small-angle X-ray scattering investigations showed that the clusters are randomly distributed in the polymer.