Modelling of cw-EPR Spectra of Propagating Radicals in Methacrylic Polymerization at Different Temperatures

The temperature dependence of the cw-EPR spectra corresponding to the propagating radical responsible for the polymerization of methacrylic monomers has been simulated by an integrated computational approach that determines the structural and magnetic parameters (via quantum mechanical calculations) and diffusive properties (via hydrodynamic based methods), which represent the overall input of the stochastic Liouville equation that yields the spectrum. The system has been modeled as a rotator with only one relaxation process, the rotation around the Cα−Cβ bond. The simulations clearly indicate that the change of the spectral shape with the temperature is essentially related to the internal flexibility of the radical end.