title: Nanoscale topography influences polymer surface diffusion.
abstract: Using high-throughput single-molecule tracking, we studied the diffusion of poly(ethylene glycol) chains at the interface between water and a hydrophobic surface patterned with an array of hexagonally arranged nanopillars. Polymer molecules displayed anomalous diffusion; in particular, they exhibited intermittent motion (i.e., immobilization and "hopping") suggestive of continuous-time random walk (CTRW) behavior associated with desorption-mediated surface diffusion. The statistics of the molecular trajectories changed systematically on surfaces with pillars of increasing height, exhibiting motion that was increasingly subdiffusive and with longer waiting times between diffusive steps. The trajectories were well-described by kinetic Monte Carlo simulations of CTRW motion in the presence of randomly distributed permeable obstacles, where the permeability (the main undetermined parameter) was conceptually related to the obstacle height. These findings provide new insights into the mechanisms of interfacial transport in the presence of obstacles and on nanotopographically patterned surfaces.
authors.affiliation: Department of Chemical and Biological Engineering, University of Colorado Boulder , Boulder, Colorado 80309, United States.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Wang
authors.forename: Chunlin
authors.initials: C
authors.lastname: He
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stoykovich
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Schwartz
mesh_terms: D004058:Diffusion; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D009010:Monte Carlo Method; D049329:Nanostructures / Q000737:chemistry*; D011092:Polyethylene Glycols; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties
chemical_list: D011092:Polyethylene Glycols; D012822:Silicon Dioxide
keywords: CTRW; obstructed diffusion; polymer; single-molecule fluorescence imaging; surface diffusion