Here, online 1 H-NMR spectroscopy has been successfully applied to investigate the kinetic parameters of radical copolymerization of styrene (St) and itaconic acid (IA). This technique was used because it allowed us to individually map out the monomer conversions of St and IA during the course of the polymerization at various conversions. This was possible because the individual contributions to the overall monomer conversion from St and IA could be measured through their nonoverlapping vinylic proton signals. The results of monomer conversion during the time in the corresponding 1 H-NMR spectra was the basis of our analysis to determine the reactivity ratios of St and IA in the solution and radical copolymerization reaction by several methods. In addition to linear least-squares methods, such as Finemann-Ross, inverted Finemann-Ross, Mayo-Lewis, Kelen-Tudos, extended Kelen-Tudos, and Mao-Huglin, a nonlinear least-square method (TidwellMortimer) was used for this purpose, at low conversions. Extended Kelen-Tudos and Mao-Huglin were applied to determine the reactivity ratio values at high conversions too.

Many reports exist in the literature about the application of 1 H and 13 C-NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on-line 1 H-NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least-squares methods such as Finemann-Ross, inverted Finemann-Ross, Mayo-Lewis, Kelen-Tudos, extended KelenTudos and Mao-Huglin. In addition, a non-linear least-square method (TidwellMortimer) was used at low conversions. Extended Kelen-Tudos and Mao-Huglin were applied to determine reactivity ratio values at high conversions as well.