Refining Reactivity Ratios in the Copolymerization of Styrene and Methyl Methacrylate by EasySpin/MATLAB Simulations and Electron Paramagnetic Resonance Spectroscopy

Electron paramagnetic resonance (EPR) spectra of the ensemble of growing macroradicals are recorded during the radical copolymerization of styrene-d8 and methyl methacrylate (MMA) for various comonomer compositions and subsequently modeled by MATLAB in combination with EasySpin simulations. Fully deuterated styrene-d8 is used to simplify the EPR spectra and to allow a clear assignment of the EPR-signals to the two different terminal units. By that approach, the macroradical fraction having styrene-d8 as terminal unit, phi(s), could directly be determined from the copolymerization spectra without concentration calibration. The so-obtained phi(s) values could not be described by the penultimate model using the literature-reported set of reactivity ratios. Consequently, phi(s,) the copolymer composition, and the overall propagation rate coefficient are adjusted in small steps simultaneously using Excel arriving at a new and more reliable set of reactivity ratios for the copolymerization of styrene and MMA.

Automated summary

The EPR spectra of growing macroradicals during the radical copolymerization of styrene-d8 and methyl methacrylate were recorded and modeled using MATLAB and EasySpin simulations, resulting in a new set of reactivity ratios for the copolymerization.