Observing Polymer Clustering in Concentrated Solutions Using Single Particle Tracking*

Non-covalent interactions governed by factors such as hydrophobicity and dipole interactions allow associating polymers to self-assemble into structures that assist in applications such as contaminant removal and drug delivery. Using single particle tracking (SPT) diffusion studies, we show that Poly(poly(ethylene glycol) Methacrylate) is a hydrophobically associating polymer, where polymer chains may diffuse individually or in clusters. Aided by the single-molecule resolution of SPT, we observe the mean square displacements of polymer chains in solution show a clear two-population division, with each population individually analyzable. This bifurcation is also seen in the distributions of final polymer displacements and the Van Hove distributions for the system. While the population of unclustered polymers shows Fickian diffusion, subdiffusive, inhibited diffusion is observed in the clustered population. Clustering behavior can be tuned by altering concentration and molecular weight of polymer, as well as the polarity of the solvent. Combined with Dynamic Light Scattering, which confirms polymer clustering as well as supplies diffusion data, and 1H NMR Diffusion-Ordered Spectroscopy, diffusion regimes up to semidilute entangled regime are experimentally observed.