Interaction forces measured between poly(N-isopropylacrylamide) grafted surface and hydrophobic particle

Naoyuki Ishida, Mikio Kobayashi

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)


The interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using an atomic force microscope. Measurements were conducted between smooth silicon wafers on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Below the lower critical solution temperature (LCST) of PNIPAAm, there were large repulsive forces between the surfaces, both on approach and separation of the surfaces. On the other hand, above LCST, attractive forces were observed both in approaching and in separating force curves. When surface hydrophobicity of the particles increased, the maximum attractive force tended to increase. The changes of hydration state of the grafted PNIPAAm chains depending on temperature are considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and the hydrophobic particles in the interaction forces is discussed.

Original languageEnglish
Pages (from-to)513-519
Number of pages7
JournalJournal of Colloid And Interface Science
Issue number2
Publication statusPublished - May 15 2006
Externally publishedYes


  • Atomic force microscope
  • Colloidal particle
  • Graft
  • Hydrophobic interaction
  • Interaction force
  • N-Isopropylacrylamide
  • Thermo-responsive polymers

ASJC Scopus subject areas

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


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