Alternating copolymerizations of polar and nonpolar cyclic olefins by ring-opening metathesis polymerization

The results from copolymerizations of polar 2,3-difunctionalized 7-oxanorbornene derivatives with a series of nonpolar cyclic olefins-cyclooctene, cyclooctadiene, cyclopentene, and norbornene-using catalysts RuCl2(=CHPh)(PCy3)(2) (1) and its mono- 1,3-dimesitylimidazolidine-2-ylidene derivative (2) are reported. The resulting polymer microstructures have been analyzed by H-1, C-13, and H-1-H-1 COSY NMR spectroscopies. Highly alternating structures were observed for the copolymerizations of endo-N-ethyl-7-oxanorbornene-2,3-dicarboxylimide (endo-3), exo,exo-7-oxanorbornene-2,3-dimethylester (exo-4), or exo-7-oxanorbornene-2,3-dicarboxylic anhydride (exo-5) with cyclooctene using catalyst 1. The rates of homopolymerizations of endo-3, exo-5, and cyclooctene were determined, Comparison with the rate of the copolymerization of endo-3 with cyclooctene reveals a rate faster than the homopolymerization of endo-3 but slower than the homopolymerization of cyclooctene. The rate of the copolymerization of exo-5 with cyclooctene was observed to be greater than the rate of homopolymerization of either monomer. The use of catalyst 2 resulted in lower levels of alternation with a tendency toward random polymerization.