Single-Molecule Tracking of Polymer Surface Diffusion

Abstract

The dynamics of polymers adsorbed to a solid surface are important in thin-film formation, adhesion phenomena, and biosensing applications, but they are still poorly understood. Here we present tracking data that follow the dynamics of isolated poly(ethylene glycol) chains adsorbed at a hydrophobic solid-liquid interface. We found that molecules moved on the surface via a continuous-time random walk mechanism, where periods of immobilization were punctuated by desorption-mediated jumps. The dependence of the surface mobility on molecular weight (2, 5, 10, 20, and 40 kg/mol were investigated) suggested that surface-adsorbed polymers maintained effectively three-dimensional surface conformations. These results indicate that polymer surface diffusion, rather than occurring in the two dimensions of the interface, is dominated by a three-dimensional mechanism that leads to large surface displacements and significant bulk-surface coupling.

Interfacial Molecular Searching Using Forager Dynamics

“…Interestingly, recent observations by our group and others suggest that the behavior of surfaceadsorbed molecules qualitatively mimics the motion favored for sparse prey searches [29][30][31][32]. In particular, proteins, polymers and small molecules all exhibit intermittent motion that corresponds to a CTRW with periods of slow or confined local diffusion alternating with flights comprising a heavy-tailed distribution.…”

Tuning the Flight Length of Molecules Diffusing on a Hydrophobic Surface

“…This feature of the step-size distributions was consistent with previous observations and modeling of desorption-mediated diffusion, i.e., flying motion. 13,31 Fitting the step-size distributions by eq 3 provided the fraction of steps representing mobility (f mobile ) ( Figure 2C Figure 2A. In general, methanol−water solutions near alkyl-coated silica exhibit very nonideal average properties.…”

Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains

“…This is due to the inherent conformational heterogeneity of polymers. Singlemolecule imaging studies have been revealing the spatiotemporal heterogeneity of polymer dynamics by visualizing the motion of individual polymer chains [32][33][34][35][36] or small fluorophores embedded in polymer matrices. [37][38][39][40][41][42][43][44] Using single-molecule localization and tracking (SMLT) technique, we previously reported the multimode diffusion of a cyclic and dicyclic polymers under the entangled conditions by incorporating a fluorophore into the chains.…”