Debye length and double-layer forces in polyelectrolyte solutions

Rafael Tadmor, Ernesto Hernández-Zapata, Nianhuan Chen, Philip Pincus, Jacob N. Israelachvili

Research output: Contribution to journalArticlepeer-review

73 Scopus citations

Abstract

We report experimental results and a theoretical analysis of the Debye length in aqueous solutions of nonadsorbing polyelectrolytes. The measurements were done using a surface forces apparatus, in which the normal forces between smooth mica surfaces in aqueous hyaluronic acid (HA) solutions were measured as a function of surface separation (to ±1 Å). HA is negatively charged and does not adsorb to the negatively charged surface of mica, as was established by optical and viscosity measurements and in agreement with the measured force-distance curves. From these measurements it appears that the multivalent polyelectrolyte is "depleted" from the gap between the surfaces. We use the mean-field Poisson-Boltzmann theory to theoretically predict the effective Debye length and double-layer force under such conditions and compare the predictions with the experimental results. The comparison gives excellent agreement and shows that the effective Debye length is determined solely by the monovalent ions in the solution. Specifically, the effective Debye length Keff -1 for the double-layer interaction is determined by au effective ionic concentration given by √nsnc, where ns and nc are the bulk negative and positive monovalent ion concentrations, respectively.

Original languageEnglish
Pages (from-to)2380-2388
Number of pages9
JournalMacromolecules
Volume35
Issue number6
DOIs
StatePublished - 12 Mar 2002
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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