Determination of Monomers Reactivity Ratios in Ethyl Acrylate-Methacrylic Acid Copolymerization by Off-Line 1H NMR

The physical, chemical and mechanical properties of polymer systems depend on the micro-structural characteristics of their macromolecular chains. Along with the most characteristic kinetic parameters in copolymerization reactions are the reactivity ratios, which give a clear idea of the average composition and the monomer sequence distribution in copolymer systems. This research studies the solution radical copolymerization of methacrylic acid (MAA)-ethyl acrylate (EA) system at low conversion with 2,2'-azobisisobutyronitrile (AIBN) as thermal initiator at 60°C in deuterated dimethyl sulfoxide (DMSO-d6) as a reaction solvent. In this case, the monomer reactivity ratios were determined using linear off-line 1H nuclear magnetic resonance spectroscopy (1H NMR) methods such as Mayo-Louis, Finemann-Ross, Inverted Finemann-Ross , Ezrielev-Brokhina-Roskin, Joshi-Joshi, Kelen-Tudos, extended Kelen- Tudos, Mao-Huglin at low and high conversions. The next estimation process in off-line 1H NMR methods were performed by applying techniques based on ordinary least square (OLS) and generalized least square (GLS). The results showed that the GLS approach compared to the OLS increased regression coefficients (R2) and the order of magnitude of parameter variances obtained from GLS was many times lower than that obtained from OLS. In addition, the monomer reactivity ratios obtained by the Mao-Huglin method and the GLS approach showed the best linear estimation.