Ring-Opening Metathesis Polymerization of 1,6-Disubstituted 1,5-Cyclooctadienes

Abstract

Ring Opening Metathesis Polymerization (ROMP) facilitates the polymerization of strained cyclic olefins to produce functionalized polyolefins. Due to the combination of the strong thermodynamic driving force for ring-opening and their kinetic stability, eight-membered cyclic olefins are widely used as ROMP monomers. While many examples of ROMP with cyclooctenes (COEs) bearing a variety of functionalities exist in the literature, ROMP using cyclooctadienes (CODs) has been limited by synthetic access to functionalized COD monomers. In light of Dr. C. Rose Kennedy’s method for enabling the synthesis of substituted CODs from abundant 1,3-dienes, the viability of these products as ROMP monomers was explored using Grubbs’ second-generation ruthenium alkylidene catalyst. 1,6-dimethyl-1,5-cyclooctadiene (1,6-DMCOD) served as a representative monomer for ROMP study. In the presence of added chain transfer agent (CTA), precision synthesis of oligomers for evaluation as high-performance lubricants was enabled. Attempted extension to high molecular weight polymer syntheses was initially hampered by trace side products from monomer synthesis, which acted as CTAs to limit chain growth, and backbiting, which occurred after full monomer consumption. Following partial removal of the side product and reaction time optimization, ROMP was attempted. Application of these insights to the precision synthesis of polyolefins with controlled microstructure holds promise for the development and study of materials with unique properties.