Ruthenium-initiated ROMP of nitrile monomers

The applicability of ruthenium alkylidenes as initiators in the ring opening metathesis polymerization (ROMP) of cyano group containing liquid crystalline norbornene derivatives has been investigated. Complexes featuring N-heterocyclic carbenes as the coligands like RuCl2(H2IMes)(PCy3)(=CHPh) polymerized (±)-exo,endo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid bis-[5-(4'-cyano-biphenyl-4-yloxy)pentyl] ester, while RuCl2(PCy3)2(=CHPh) failed. Especially RuCl2(H2IMes)(=CH-o-(Pri2 )O–C6H4) proved to be an effective initiator, operating also in ambient conditions. The corresponding side chain liquid crystalline polymers were isolated in high yields and showed considerably narrow polydispersities. The thermal properties of the polymers were compared to the corresponding polymers prepared by a molybdenum based initiator system. Only subtle differences were found, proving at the first time the suitability of ruthenium initiators for the preparation of cyano group substituted side chain liquid crystalline polymers.