Permanent and reversible gels: Transport of guests and guest-host interactions

We describe the application of electron spin resonance imaging (ESRI) for m easuring macroscopic diffusion coefficients of paramagnetic guests in polym eric systems. The ESRI method is based on encoding spatial information in t he ESR spectra via magnetic field gradients, and on simulating the time evo lution of the spectra in order to extract the diffusion coefficient, D. Thi s paper presents one dimensional (1D) ESRI experiments planned to study (a) the dependence of the diffusion coefficients of probes on the presence of permanent crosslinks in gels, and (b) the effect of the probe site on the t ransport rates in self-assembled polymers. These effects were investigated, respectively, in two types of gels: chemically crosslinked (permanent) hyd rogels, and reversible gels formed by self-assembly of polymeric surfactant s.