Synthesis and characterization of stereoregular ethylene-vinyl alcohol copolymers made by ring-opening metathesis polymerization

The syntheses of regioregular as well as stereoregular ethylene-vinyl alcohol (EVOH) copolymers by ring-opening metathesis polymerization (ROMP) with ruthenium catalysts are reported. Symmetric cyclooctenediol monomers were protected as acetates, carbonates, or acetonides to temporarily increase ring strain as well as impart solubility to the monomer. Polymer molecular weights could be easily controlled by either varying the monomer-to-catalyst ratio or by the addition of a chain transfer agent. Hydrogenation and subsequent deprotection of the ROMP polymers afforded the EVOH materials in high yields, and the structures were confirmed by H-1 NMR and C-13 NMR spectroscopies. Thermal properties of the corresponding EVOH copolymers are reported and suggest that differences in diol stereochemistry significantly affect the polymer morphology.