Adsorption of poly(styrenesulfonate) to the air surface of water by neutron reflectivity

H. Yim, M. Kent, A. Matheson, R. Ivkov, S. Satija, J. Majewski, G. S. Smith

Research output: Contribution to journalArticle

Abstract

The adsorption of the strong polyelectrolyte poly(styrenesulfonate) (PSS) to the air surface of dilute aqueous solutions was investigated as a function of molecular weight and salt concentration. Detailed segment profiles of the deuterated polymer were determined by neutron reflection. Surface activity was also examined through surface tension measurements. In general, the segment profiles are composed of a thin layer (10-20 angstrom thick) of high concentration at the air surface, followed by a distinct second layer of much lower segment concentration that extends to larger depths into the liquid. The high segment density at the air surface is due to a strong surface attraction, arising from the low surface energy of the PSS backbone relative to the surface tension of water. At low salt concentration, the profiles tend toward a single dense layer, suggesting that the chains lie nearly flat at the interface in that limit. The adsorbed amount increases with salt concentration, with a stronger dependence for higher molecular weight chains. The adsorbed amounts at the air/water interface are higher than reported previously for PSS adsorbed onto neutral solid surfaces, consistent with the fact that the air-liquid interface provides a stronger surface attraction. While the trends of adsorbed amount with salt concentration and molecular weight are in good agreement with numerical self-consistent-field lattice calculations, the measured bilayer profiles are rather different from the smoothly decaying theoretical profiles. The surface tensions of the PSS solutions are significantly lowered relative to those of pure salt solutions. Combining the reflectivity and surface tension measurements, an approximately linear relationship is established between the surface pressure and the PSS adsorbed amount.

Original languageEnglish (US)
Pages (from-to)6126-6133
Number of pages8
JournalMacromolecules
Volume33
Issue number16
DOIs
StatePublished - Aug 8 2000
Externally publishedYes

ASJC Scopus subject areas

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

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  • Cite this

    Yim, H., Kent, M., Matheson, A., Ivkov, R., Satija, S., Majewski, J., & Smith, G. S. (2000). Adsorption of poly(styrenesulfonate) to the air surface of water by neutron reflectivity. Macromolecules, 33(16), 6126-6133. https://doi.org/10.1021/ma000266q