Probe diffusion in aqueous poly(vinyl alcohol) solutions studied by fluorescence correlation spectroscopy.
We report fluorescence correlation spectroscopy measurements of the translational diffusion coefficient of various probe particles in dilute and semidilute aqueous poly(vinyl alcohol) solutions. The range of sizes of the particles (fluorescent molecules, proteins, and polymers) was chosen to explore various length scales of the polymer solutions as defined by the polymer-polymer correlation length. For particles larger than the correlation length, we find that the diffusion coefficient, D, decreases exponentially with the polymer concentration. This can be explained by an exponential increase in the solution viscosity, consistent with the Stokes-Einstein equation. For probes on the order of the correlation length, the decrease of the diffusion coefficient cannot be accounted for by the Stokes-Einstein equation, but can be fit by a stretched exponential, D approximately exp(-alphacn), where we find n = 0.73-0.84 and alpha is related to the probe size. These results are in accord with a diffusion model of Langevin and Rondelez (Polymer 1978, 19, 1875), where these values of n indicate a good solvent quality.
Michelman-Ribeiro
Ariel
A
Laboratory of Integrative and Medical Biophysics, National Institutes of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Horkay
Ferenc
F
Nossal
Ralph
R
Boukari
Hacène
H
D004058:Diffusion; D008956:Models, Chemical; D011142:Polyvinyl Alcohol / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014867:Water / Q000737:chemistry
D012996:Solutions; D014867:Water; D011142:Polyvinyl Alcohol