Solution and surface charge properties of shell cross-linked knedel nanoparticles
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Solution-state characterizations of poly(4-vinylpyridine):polystyrene (PVP:PS) shell cross-linked knedel nanoparticles (SCK's) are described. A combination of techniques, including dynamic light scattering, electrophoretic light scattering, and analytical ultracentrifugation, are used to determine the hydrodynamic diameter, surface charge characteristics, molecular weight, and aggregation number of the SCK's and their micelle precursors. The use of analytical ultracentrifugation is highlighted because of the wealth of information it provides in characterizing SCK solution behavior. The analysis of SCK's indicates that particle diameter, molecular weight, and aggregation increase with increasing PS chain length of the PVP:PS block copolymer used to prepare the SCK. Measurements of electrophoretic mobility and zeta potential via electrophoretic light scattering point to partial burial of charge below the particle surface of quaternized PVP units comprising the shell of the SCK. By contrast, the characterization of corresponding solution properties for the non-cross-linked micelle precursors is problematic due to significant particle heterogeneity and nonideal solution behavior. The comparison of solution data for SCK's and micelle precursors clearly indicates stabilization of SCK particles is achieved through shell cross-linking.