Nano fillers are known to dramatically affect the rheological properties of polymer systems. Understanding and manipulating the rheological behavior of carbon nanotubes (CNTs)-loaded polymer system is of high importance for achieving optimal performance. The remarkable effect of CNTs on the polymer system rheology is mainly associated with their high aspect ratio, enabling them to percolate and form a network structure. The NT network inhibits the polymer chain mobility already at very low filler concentration (~0.1 vol%). In this study, we explored the mobility (diffusivity) of epoxy chains when loaded by CNTs using NMR diffusion experiments. At the molecular level, we detect the self-diffusion coefficient of CNT-bound epoxy chains and correlated their concentration to bulk rheological properties (e.g., viscosity and storage modulus). The concentration of CNT-bound epoxy molecules scales with the rheological percolation, specifically, with the crossover volume fraction in which the polymer transforms for liquid into solid-like behavior (G’= G’’). We therefore suggest that diffusion NMR can be employed as an indicative characterization tool for rheological and interface properties of nanocomposite systems. Reference: 1. Roey Nadiv, Michael Shtein, Alva Peled, Gleb Vasilyev, Eyal Zussman and Oren Regev. Composites Science and Technology, 2016, 133, 192-199.