Imaging Heterogeneous 3D Dynamics of Individual Solutes in a Polyelectrolyte Brush

Understanding molecular transport in polyelectrolytebrushes (PEBs)is crucial for applications such as separations, drug delivery, anti-fouling,and biosensors, where structural features of the polymer control intermolecularinteractions. The complex structure and local heterogeneity of PEBs,while theoretically predicted, are not easily accessed with conventionalexperimental methods. In this work, we use 3D single-molecule trackingto understand transport behavior within a cationic poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA)brush using an anionic dye, Alexa Fluor 546, as the probe. The analysisis done by a parallelized, unbiased 3D tracking algorithm. Our resultsexplicitly demonstrate that spatial heterogeneity within the brushmanifests as heterogeneity of single-molecule displacements. Two distinctpopulations of probe motion are identified, with anticorrelated axialand lateral transport confinement, which we believe to correspondto intra- vs inter-chain probe motion.

Automated summary

In this work, we use 3D single-molecule tracking to study the transport behavior in a cationic poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA) brush using an anionic dye, Alexa Fluor 546, as the probe. Our results show that the spatial heterogeneity within the brush leads to heterogeneity of single-molecule displacements. We identify two distinct populations of probe motion, with anticorrelated axial and lateral transport confinement.