title: Hopping Diffusion of Nanoparticles in Polymer Matrices.
abstract: We propose a hopping mechanism for diffusion of large nonsticky nanoparticles subjected to topological constraints in both unentangled and entangled polymer solids (networks and gels) and entangled polymer liquids (melts and solutions). Probe particles with size larger than the mesh sizeaxof unentangled polymer networks or tube diameteraeof entangled polymer liquids are trapped by the network or entanglement cells. At long time scales, however, these particles can diffuse by overcoming free energy barrier between neighboring confinement cells. The terminal particle diffusion coefficient dominated by this hopping diffusion is appreciable for particles with size moderately larger than the network mesh sizeaxor tube diameterae. Much larger particles in polymer solids will be permanently trapped by local network cells, whereas they can still move in polymer liquids by waiting for entanglement cells to rearrange on the relaxation time scales of these liquids. Hopping diffusion in entangled polymer liquids and networks has a weaker dependence on particle size than that in unentangled networks as entanglements can slide along chains under polymer deformation. The proposed novel hopping model enables understanding the motion of large nanoparticles in polymeric nanocomposites and the transport of nano drug carriers in complex biological gels such as mucus.
authors.affiliation: Department of Applied Physical Sciences, University of North Carolina , Chapel Hill, North Carolina 27599-3287, United States ; Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States ; School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Li-Heng
authors.initials: LH
authors.lastname: Cai
authors.affiliation: P. N. Lebedev Physics Institute, Russian Academy of Sciences , Moscow 117924, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Panyukov
authors.affiliation: Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599-3290, United States ; Department of Applied Physical Sciences, University of North Carolina , Chapel Hill, North Carolina 27599-3287, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Rubinstein