Olefin metathesis routes to ROMP-active carbonyl-functionalized monomers and polymers.

摘要

This thesis reports the synthesis of unsaturated lactones and lactams by ring-closing metathesis (RCM) and the evaluation of these compounds as monomers in ring-opening metathesis polymerization (ROMP).While conventional ring-expansion methodologies have shown limited success in the synthesis of unsaturated 7-membered lactones, RCM afforded the desired products in excellent yields when the dienyl ester substrate was coordinated to a sterically demanding aluminum-based LA. Extension of this methodology to the synthesis of 7-membered lactams and 8-membered lactones and substituted cyclooctenes was then explored. The effects of substrate coordination to the bulky LA were evaluated using spectroscopic, crystallographic, and theoretical methods.ROMP-based polyesters were synthesized from beta,gamma- and gamma,delta-unsaturated 7-membered lactones that differ in ring strain and ability to form chelates to the metal center once ring-opened. Studies indicate that many olefin-containing species were present and interconverted during polymerization therefore, the release of ring strain in the monomer was not the primary driving force for the formation of high-molecular-weight polymer, as in the case of the ROMP of traditional monomers such as norbornene. From these results, it is apparent that a combination of effects, including monomer-catalyst interactions, substitution near the olefin groups on the polymer backbone, and monomer ring strain, influences the ability of a monomer to undergo ROMP and to control polymer molecular weight.As a route towards unsaturated polyamides, the ROMP of two unsaturated lactams that differ in nitrogen substitution was studied. While the tertiary lactam did not undergo ring-opening to an appreciable degree, the secondary lactam readily underwent metathesis, but unexpectedly yielded cyclic oligomers. The intrachain backbiting that led to these products was likely a result of poor product solubility and coordination of the growing polymer chain to the catalyst. Decomposition of the metathesis catalyst was observed, a factor which may have prevented complete monomer consumption and conversion of the cyclic oligoamides to high-molecular-weight polymers.