Single-Molecule Observation of Long Jumps in Polymer Adsorption

TL;DR

This study uses single-molecule fluorescence imaging to reveal that polymer chains can perform rapid, long jumps on surfaces before stabilizing or detaching, challenging traditional crawling models.

Contribution

It demonstrates the existence of rapid surface diffusion jumps in polymer adsorption, characterized by a truncated Levy distribution, providing new insights into adsorption dynamics.

Findings

Polymer chains can re-adsorb at different locations after initial contact.

Surface diffusion occurs faster than classical crawling models predict.

Jump sizes follow a truncated Levy distribution with slope -2.5.

Abstract

Single-molecule fluorescence imaging of adsorption onto initially-bare surfaces shows that polymer chains need not localize immediately after arrival. In a system optimized to present limited adsorption sites (quartz surface to which polyethylene glycol (PEG) is exposed in aqueous solution at pH = 8.2) we find that some chains diffuse back into bulk solution and re-adsorb at some distance away, sometimes multiple times before either they localize at a stable position or else diffuse away into bulk solution. This mechanism of surface diffusion is considerably more rapid than the classical model in which adsorbed polymers crawl on surfaces while the entire molecule remains adsorbed. The trajectories with jumps follow a truncated Levy distribution of step size with limiting slope -2.5, consistent with a well-defined, rapid surface diffusion coefficient over the times we observe.