Salt-induced structural behavior for poly(N-isopropylacryamide) grafted onto solid surface observed directly by AFM and QCM-D

Naoyuki Ishida, Simon Biggs

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

The salt-induced structural changes of an end-grafted poly(N- isopropylacrylamide) (PNIPAM) layer on a silica substrate were investigated in sodium sulfate solutions using an atomic force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). A PNIPAM layer was grafted onto the silicon wafer surface by free radical polymerization of NIPAM to obtain a high molecular weight polymer layer with low grafting density overall. AFM images of the coated surface were featureless at low salt concentrations commensurate with a brush-like layer. At salt concentrations ≥ 0.11 M, a large number of domain structures, with a characteristic size of ∼100 nm, were seen on the surface commensurate with a collapse of the brush-like layer into mushroom-like aggregates. This critical concentration for brush collapse is in good agreement with the concentration range of between 0.1 and 0.2 M, at which the phase transition of the bulk PNIPAM is reported. Both the frequency and the dissipation data obtained using a QCM-D also showed a significant change at this concentration indicative of the layer collapse. Further analysis of these data confirmed that the observed PNIPAM structural transition was caused by a collapse of the brush-like structure as a result of dehydration of the polymer chains.

Original languageEnglish
Pages (from-to)9045-9052
Number of pages8
JournalMacromolecules
Volume40
Issue number25
DOIs
Publication statusPublished - Dec 11 2007
Externally publishedYes

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Quartz crystal microbalances
Brushes
Microscopes
Salts
Polymers
Sodium sulfate
Free radical polymerization
Dehydration
Silicon wafers
Silicon Dioxide
Phase transitions
Molecular weight
Silica
poly-N-isopropylacrylamide
Substrates

ASJC Scopus subject areas

  • Materials Chemistry

Cite this

Salt-induced structural behavior for poly(N-isopropylacryamide) grafted onto solid surface observed directly by AFM and QCM-D. / Ishida, Naoyuki; Biggs, Simon.

In: Macromolecules, Vol. 40, No. 25, 11.12.2007, p. 9045-9052.

Research output: Contribution to journalArticle

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