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.

Single-Particle Tracking in Poly(Ethylene Glycol) Diacrylate: Probe Size Effect on the Diffusion Behaviors of Nanoparticles in Unentangled Polymer Solutions

“…The data seems to suggest that the particle was able to diffuse more freely, less restricted in the second microstructured PEGDA domain-like environment, because of its more elongated, 1D-like trajectory appearance (vs the blob-like portion of the trajectory, Figure A). The presence of two distinct polymer regions in concentrated poly(ethylene glycol) methacrylate solutions has been previously revealed using SPT . By tracking fluorescence-labeled poly(ethylene glycol) methacrylate in solution, the authors were able to assign one microstructured region to clusters formed by associating polymers via hydrophobic interactions and the other one to polymer phase consisting of single polymer chains diffusing in the solution.…”

Extreme Dependence of Dynamics on Concentration in Highly Crowded Polyelectrolyte Solutions

“…For neutral polymers, scaling laws of D~ϕ -0.54 , D~ϕ -1.85 , and D~ϕ -2.33 are expected for the semidilute unentangled, semidilute entangled, and concentrated regimes, respectively, which we confirmed for pPEGMA in our previous study. (46,59) For polyelectrolyte solutions, the expected scaling laws are derived for the semidilute entangled regime as D~ϕ -0.50 in the low salt regime and D~ϕ -1. 75 in the high salt regime.…”

“…These diffusivity results are shown in Figure2as a function of volume fraction, ϕ. For comparison, we have also included diffusion coefficients obtained over a similar range of concentrations for pPEGMA, a neutral polymer from our recent previous study (46). Between 1 and 10 wt%, the diffusion…”

Extreme Dependence of Dynamics on Concentration in Highly Crowded Polyelectrolyte Solutions

“…This allows us to directly probe the dynamics of polyelectrolytes on an individual chain level, revealing any heterogeneities, departures from Fickian diffusion, or interesting diffusive behavior that may arise in the system. [46][47][48][49] In this work, we study the diffusivity of polylysine (PL) in various matrices to determine the role that the polymer environment plays on chain mobility. We use PL as a model polyelectrolyte due to its presence in other literature, commercial availability, and accessible pKa.…”