An Examination of the Kinetics of the Ring-Opening Metathesis Polymerization (ROMP) of a 7-oxanorbornene Derivative with Grubbs' Catalyst

Abstract

The study of ring-opening metathesis polymerization (ROMP) has become increasingly important over the past two decades. ROMP is unusual in that it provides a route to polymers with a high degree of unsaturation in the backbone, as it preserves all double bonds found in the monomeric units. Commercially, this process is used in the synthesis of several rubbers used in auto-body parts, such as Metton, Vestenamer and Norsorex. We have been examining the kinetics of a living ROMP reaction between Grubbs' catalyst and a 7-oxanorbornene derivative. These experiments were conducted in two phases. In the first phase, the kinetics of propagation were investigated using a JEOL 400 MHiz FT-NMR spectrometer to measure the decrease in monomer concentration over time relative to a ferrocene internal standard. This data was used to calculate the rate constant of propagation, k[p], by assuming that the system possessed the kinetics typical of living systems. This procedure was repeated over a range of temperatures. The Arrhenius equation was then used to calculate E[a] and [delta]S[++] for propagation. The second phase was designed to examine initiation kinetics. An HP diode-array UV-visible spectrometer was used to monitor the decrease in the concentration of the uninitiated catalyst over time. This data was then used to calculate the rate constant of initiation, k[i]. As with the propagation studies, k[i] was determined for several temperatures, after which E[a] and [delta]S[++] of initiation were calculated using the Arrhenius equation. The time scales of initiation and propagation, denoted by [T][i] and [T][p], were also calculated and compared to show that this reaction is in fact a living system.