We propose a new method for the determination of reactivity ratios of monomers in a chain copolymerization that follows terminal model kinetics. We assume that the monomers consumed during copolymerization are accumulated in the polymer backbone without undergoing any side reactions. We used 1H-NMR spectroscopy as a tool to follow the monomer consumption with time, and hence accurately determined the reactivity ratio from non-linear least square (NLLS) fitting of Mayo-Lewis plot. We considered 100 to 130 data points for better NLLS fitting of Mayo-Lewis plot, whether conventional method does fitting with 7 to 10 data points. The data points were obtained from in-situ NMR spectroscopy experiments of different feed compositions of monomers. The methodology was validated using styrene (St) and methyl methacrylate (MMA) as a model system. We obtained rst= 0.58±0.02 and rMMA= 0.49±0.02, which is similar to other literature reports following conventional methods. Our methodology requires very low quantities of monomer, unlike conventional methods. Additionally, with this methodology we can bypass a number of practical issues that appear in conventional methods, such as separation of unreacted monomer, which is especially when it aggregates with polymer; inaccurate determination of unreacted and consumed monomer due to lack of consideration of the relaxation times of the protons of interest. We copolymerized N,N-dimethylacrylamide (DMA) with 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA) and with 2-(N-ethylperfluorooctanesulfonamido)ethyl methacrylate (FOSM). With our unique methodology, we successfully determined the reactivity ratios of two separate copolymerization systems as rDMA= 0.93±0.04, rFOSA= 1.42±0.07 and rDMA= 1.13±0.03, rFOSM= 3.51±0.08.

Simple and accurate determination of reactivity ratios of chain copolymerization following terminal model by in-situ 1H-NMR technique

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.