End-grafted low-melecular-weight PNIPAM does not collapse above the LCST

X. Zhu, C. Yan, F. M. Winnik, Deborah E Leckband

Research output: Contribution to journalArticle

Abstract

The interfacial properties of end-grafted temperature-responsive poly(N-isopropylacryamide) (PNIPAM) were quantified by direct force measurements both above and below the lower critical solution temperature (LCST) of 32 °C. The forces were measured between identical, opposing PNIPAM films and between a PNIPAM film and a lipid membrane. At the grafting densities and molecular weights investigated, the polymer extension did not change significantly above the LCST, and the polymers did not adhere. Below the LCST, the force-distance profiles suggest a vertical phase separation, which results in a diluter outer layer and a dense surface proximal layer. At large separations, the force profiles agree qualitatively with simple polymer theory but deviate at small separations. Importantly, at these low grafting densities and molecular weights, the end-grafted PNIPAM does not collapse above the LCST. This finding has direct implications for triggering liposomal drug release with end-grafted PNIPAM, but it increases the temperature range where these short PNIPAM chains function as steric stabilizers.

Original languageEnglish (US)
Pages (from-to)162-169
Number of pages8
JournalLangmuir
Volume23
Issue number1
DOIs
StatePublished - Jan 2 2007

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low weight
Polymers
Temperature
temperature
molecular weight
polymers
Molecular weight
Force measurement
Membrane Lipids
profiles
Phase separation
lipids
surface layers
drugs
membranes
Pharmaceutical Preparations

ASJC Scopus subject areas

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

Cite this

End-grafted low-melecular-weight PNIPAM does not collapse above the LCST. / Zhu, X.; Yan, C.; Winnik, F. M.; Leckband, Deborah E.

In: Langmuir, Vol. 23, No. 1, 02.01.2007, p. 162-169.

Research output: Contribution to journalArticle

Zhu, X. ; Yan, C. ; Winnik, F. M. ; Leckband, Deborah E. / End-grafted low-melecular-weight PNIPAM does not collapse above the LCST. In: Langmuir. 2007 ; Vol. 23, No. 1. pp. 162-169.
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