The molecular motions of spin probes at the interphase region of poly (methyl methacrylate) particles sterically stabilized by polyisobutylene (PIB) were studied by ESR spectroscopy. The correlation times (tau) were measured by using the methods of Freed and Kivelson. Activation energies for different modes of motion were calculated at wide temperature range between -140 and 140-degrees-C. Viscosities were estimated in methanol saturated PIB channels in the polymer particles.