Ionic strength dependent forces between end-grafted Poly(sulfobetaine) films and mica

Syeda Tajin Ahmed, Jason J. Madinya, Deborah E. Leckband

Research output: Contribution to journalArticlepeer-review


The molecular surface properties of zwitterionic polymer coatings are central to their ultra-low fouling properties and effectiveness as steric stabilizers in concentrated salt solutions. Here, Surface Force Apparatus measurements quantified the molecular forces between end-grafted poly(sulfobetaine) methacrylate thin films and mica, as a function of the chain grafting density and ionic strength. These results demonstrate that, at the ionic strengths considered, end-grafted poly(sulfobetaine) films can be described by models for polymers in good solvent. Parameters determined from data fits to the Milner-Witten-Cates or Dolan and Edwards models for dense or dilute chains, respectively, varied with ionic strength, in ways that reflect poly(sulfobetaine) swelling and the increased excluded volume strength of chain segments. These force measurements provide new insight into how polymer coverage and salt cooperate to regulate repulsive poly(sulfobetaine) steric barriers. These findings have implications for the design of grafted poly(sulfobetaine) as colloidal stabilizers or nonfouling surface coatings.

Original languageEnglish (US)
Pages (from-to)298-306
Number of pages9
JournalJournal of Colloid And Interface Science
StatePublished - Jan 15 2022


  • Antipolyelectrolyte effect
  • Interaction forces
  • Surface Force Apparatus
  • Surface forces
  • Zwitterionic polymers

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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