Fractionation methods photon correlation spectroscopy

Effect of PVA Molecular Weight on Adsorbed Layer Thickness. Figure 4 shows the variation of reduced viscosity with volume fraction for the bare and PVA-covered 190nm-size PS latex particles. For the bare particles, nre(j/ is independent of and the value of the Einstein coefficient is ca. 3.0. For the covered particles, rired/ t increases linearly with tp. Table IV gives the adsorbed layer thicknesses calculated from the differences in the intercepts for the bare and covered particles and determined by photon correlation spectroscopy, as well as the root-mean-square radii of gyration of the free polymer coil in solution. The agreement of the adsorbed layer thicknesses determined by two independent methods is remarkable. The increase in adsorbed layer thickness follows the same dependence on molecular weight as the adsorption density, i.e., for the fully hydrolyzed PVA s and... 

There are, however, some problems with this method. First, high molecular weight fractions are not soluble in the strongest solvent, A-methyl pyrroli-done, for emeraldine base. Second, Wessling has shown by membrane filtration and photon correlation spectroscopy that these transparent, clear blue liquids are in fact dispersions and not solutions. 

Caldwell, K.D. Li, J. Emulsion characterization by the combined sedimentation field-flow fractionation-photon correlation spectroscopy methods. J. Colloid Interface Sci. 1989,132, 256-268. 

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