Determination of Hydrophobic Polymer Clustering in Concentrated Aqueous Solutions through Single-Particle Tracking Diffusion Studies

Abstract

Noncovalent 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(ethylene glycol monomethacrylate) (pPEGMA) is a hydrophobically associating polymer, where polymer chains may diffuse individually or in clusters. Aided by the single-molecule resolution of SPT, we observe that the mean-squared displacements of pPEGMA chains in solution show a clear two-population division, which corresponds to unimers and clusters in our hypothesis. This bifurcation is also seen in the distributions of polymer mean-squared displacements and the van Hove distributions. Clustering behavior can be tuned by altering the concentration and molecular weight of the polymer, as well as the polarity of the solvent. Combined with dynamic light scattering (DLS) and diffusion ordered spectroscopy (DOSY), polymer diffusive regimes up to the semidilute entangled regime are experimentally observed.