Tuning the Interfacial Properties of Grafted Chains with a pH Switch

X. Zhu, J. DeGraaf, F. M. Winnik, D. Leckband

Research output: Contribution to journalArticlepeer-review


Environmentally responsive, water-soluble polymers have a wide variety of uses ranging from drug delivery to viscosity modifiers. Their utility lies in the ability to use environmental perturbations to dramatically alter the material properties. Here, we describe the interfacial properties of a hydrophobically modified copolymer of N-sopropylacrylamide and glycinylacrylamide (NIPAM-N-Gly-(C18) 2), which is both temperature and pH responsive. Direct force measurements quantified the substantial pH-dependent change in the molecular properties of end-grafted NIPAM-N-Gly-(C18) 2 monolayers. At pH 8.0, where the glycine side chains are ionized, the polymers exhibit stereotypical polyelectrolyte behavior. Side chain neutralization at pH 5.0 causes a substantial decrease in the film thickness, and the polymer films adhere strongly. The adhesion is presumably through H-bonding between the glycine side chains. Our findings revealed the likely molecular basis of pH-dependent changes in the copolymer films and identified clear design criteria for tuning the interfacial properties of these polymer films.

Original languageEnglish (US)
Pages (from-to)1459-1465
Number of pages7
Issue number4
StatePublished - Feb 17 2004

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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