Fluorescent polyolefins by ring-opening metathesis polymerization of 3-substituted cyclooctenes

The Ring Opening Metathesis Polymerization (ROMP) of 3-substituted cyclooctene monomers having side chains functionalized with fluorescent coumarin or carbazole units was successfully accomplished using commercial Grubbs' second and third generation catalysts. The resulting polymers were highly regio-(head to tail) and stereo-regular (trans) and showed thermal properties strongly dependent on the structure of their pendant moieties. The photoluminescent behavior of the synthesized polymers was investigated in solution and in the solid state. Interestingly, in the solid state strong excimer emission was observed for the carbazole-containing polymers because of the intra-and intermolecular coupling of pendant carbazole units. Following the chemical hydrogenation of the carbazole-containing polymer backbone, a linear polyethylene derivative was obtained that exhibited the same fluorescence emission behavior as its unsaturated counterpart. A functionalized polycyclooctene was also synthesized by copolymerization of cyclooctene with a low amount of carbazole-containing monomer. Subsequent saturation of the polymer backbone provided the corresponding functionalized polyethylene. Both of these polymers showed fluorescence emission from isolated carbazole units and chemicophysical properties typical of pristine polycyclooctenes and polyethylenes, suggesting that they may have potential applications as fluorescent markers for these materials, as preliminarily confirmed by the preparation of a fluorescent blend of the hydrogenated copolymer (1 wt%) with commercial low-density polyethylene.