Translational Diffusion of Paramagnetic Tracers in HEMA Gels and in Concentrated Solutions of PolyHEMA by 1D Electron Spin Resonance Imaging

Suitable experimental techniques and theoretical deconvolution and simulation procedures applicable to determination of concentration profiles of paramagnetic particles by ESRI technique and for subsequent determination of diffusion coefficients of paramagnetic tracers in the sample were proposed. The macroscopic diffusion coefficients, D, of paramagnetic tracers in cross-linked 2-hydroxyethyl methacrylate (HEMA) gels equilibrium-swollen with methanol and in polyHEMA methanolic solutions were measured by one-dimensional electron spin resonance imaging (1D ESRI). Both types of the matrix were characterized by dynamic correlation length, L h, determined by dynamic light scattering (DLS). The dependence of diffusion coefficients on concentration of polyHEMA in methanolic solutions was well fitted within both Phillies' and Petit's models at approximately the same level of accuracy. A slower diffusion of the tracers was found in HEMA gels compared with the solution containing the same concentration of polyHEMA and even with the solution characterized by the same hydrodynamic mean distance between adjacent entanglement points. The results demonstrate the high potential of the 1D ESRI technique and of the data processing methods developed for measurements of diffusion coefficients of paramagnetic tracers in polymer systems.