Interactions between polymer brushes: Varying the number of end-attaching groups

Iain E. Dunlop, Wuge H. Briscoe, Simon Titmuss, Giorgos Sakellariou, Nikolaos Hadjichristidis, Jacob Klein*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


We use a surface force balance (SFB) to study the normal interactions between polymer brushes, which are self-assembled from solution. They consist of polystyrene (PS) chains in toluene (neutral chains in a good solvent) anchored on the interacting mica surfaces via sulfozwitterionic end groups. The properties of the brush depend on the length, N, of the chain, and the energy, αkBT, with which the end group adsorbs on the surface. In contrast to earlier studies where N was varied, we attempt to vary the sticking energy by using polymer chains with one, two, and three zwitterions attached to their ends. We use the theory of Alexander and de Gennes to predict how the normal force profile should vary with α and N, finding, for example, that the brush height L0 obeys L0 = a ·3/5 · α2/5. Surprisingly, our measurements show that the grafting density does not vary significantly between polymers with 1,2, and 3 end groups. This could be attributed to dtpole-dipole interactions between the zwitterions themselves. It is also possible that the effect could be kinetic; that the brush is unable to reach its equilibrium state because successive polymer chains are hindered from attaching to the surface by those already in the brush. Measurements on longer time scales will be necessary to determine whether kinetic effects are important.

Original languageEnglish (US)
Pages (from-to)2443-2450
Number of pages8
JournalMacromolecular Chemistry and Physics
Issue number18
StatePublished - Dec 8 2004


  • Multi ω-sulfozwitterionic polystyrenes
  • Polymer brushes
  • Polystyrene
  • Surface force balance
  • Surfaces

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry


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