Tethered Poly(2-isopropyl-2-oxazoline) Chains: Temperature Effects on Layer Structure and Interactions Probed by AFM Experiments and Modeling

Research output: Contribution to journalArticle

Abstract

Thermoresponsive polymer layers on silica surfaces have been obtained by utilizing electrostatically driven adsorption of a cationic-nonionic diblock copolymer. The cationic block provides strong anchoring to the surface for the nonionic block of poly(2-isopropyl-2-oxazoline), referred to as PIPOZ. The PIPOZ chain interacts favorably with water at low temperatures, but above 46 degrees C aqueous solutions of PIPOZ phase separate as water becomes a poor solvent for the polymer. We explore how a change in solvent condition affects interactions between such adsorbed layers and report temperature effects on both normal forces and friction forces. To gain further insight, we utilize self-consistent lattice mean-field theory to follow how changes in temperature affect the polymer segment density distributions and to calculate surface force curves. We find that with worsening of the solvent condition an attraction develops between the adsorbed PIPOZ layers, and this observation is in good agreement with predictions of the mean-field theory. The modeling also demonstrates that the segment density profile and the degree of chain interpenetration under a given load between two PIPOZ-coated surfaces rise significantly with increasing temperature.

Details

Authors
  • Junxue An
  • Xiaoyan Liu
  • Per Linse
  • Andra Dedinaite
  • Francoise M. Winnik
  • Per M. Claesson
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Physical Chemistry
Original languageEnglish
Pages (from-to)3039-3048
JournalLangmuir
Volume31
Issue number10
Publication statusPublished - 2015
Publication categoryResearch
Peer-reviewedYes