Polymer-salt-solvent effects on colloidal interactions

Conference Dates

July 31-August 4, 2017


Model, waterborne systems of fluorinated spheres bearing surface grafts of poly(ethylene glycol) (PEG) have been studied as salting-out electrolyte (e.g., Na2CO3) is added. The ions are thought to be depleted in the vicinity of the PEG corona, leading to short-range attractions on overlap of such ion-depleted regions. The resulting attraction is shown to be of sufficient strength at high ion concentration to cause aggregation in spite of the near absence of the usual van der Waals attraction between particles. The dependence of the electrolyte- induced instability on PEG chain length has been evaluated. These measurements demonstrate that, with some reservation regarding the effect of grafting density, the stability is greatly improved for particles grafted with shorter chains. For very short chains these water-based systems become impervious to added electrolyte.

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