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Scaling Behavior of Dendritic Nanoparticle Mobility in Semidilute Polymer Solutions

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journal contribution
posted on 27.10.2015, 00:00 by Daan W. de Kort, Wolf H. Rombouts, Freek J. M. Hoeben, Henk M. Janssen, Henk Van As, John P. M. van Duynhoven
In our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly­(ethylene glycol) (PEG, Mw = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (dh = 3.4–11.0 nm) and with internal 19F moieties allow for background-free 19F NMR diffusion measurements. This way, we were able to assess the self-diffusion coefficients as a function of particle diameter and length scales (correlation length, tube diameter, polymer radius of gyration) with high resolution. Scaling arguments allowed us to visualize a clear crossover between particles probing a lower apparent viscosity to near macroviscosity when the nanoparticle size is comparable to the PEG polymer coil size. The same arguments are shown to correctly predict particle diffusion coefficients as a function of polymer concentration when the particles are smaller than the polymer coils.