Adsorbed layer structure of a weak polyelectrolyte studied by colloidal probe microscopy and QCM-D as a function of pH and ionic strength

Notley, Shannon M., Biggs, Simon, Craig, Vincent S. J. and Wagberg, Lars (2004) Adsorbed layer structure of a weak polyelectrolyte studied by colloidal probe microscopy and QCM-D as a function of pH and ionic strength. Physical Chemistry Chemical Physics, 6 9: 2379-2386. doi:10.1039/b401376j


Author Notley, Shannon M.
Biggs, Simon
Craig, Vincent S. J.
Wagberg, Lars
Title Adsorbed layer structure of a weak polyelectrolyte studied by colloidal probe microscopy and QCM-D as a function of pH and ionic strength
Journal name Physical Chemistry Chemical Physics   Check publisher's open access policy
ISSN 1463-9076
1463-9084
Publication date 2004-05-07
Year available 2004
Sub-type Article (original research)
DOI 10.1039/b401376j
Open Access Status Not yet assessed
Volume 6
Issue 9
Start page 2379
End page 2386
Total pages 8
Place of publication Cambridge, United Kingdom
Publisher Royal Society of Chemistry
Language eng
Abstract The adsorbed layer structure of a weak polyelectrolyte poly(2- vinylpyridine), on silica and mica, has been studied using colloidal probe microscopy (CPM) and the quartz crystal microbalance (QCM-D). The adsorbed layer structure was found to be highly dependent on both the solution conditions from which it was adsorbed and the molecular weight. Conditions were altered to favour both flat adsorbed layers and the development of significant steric layers. The structural reconformation of the large steric layer was furthermore studied as a function of pH. The equilibrium interaction force, measured using CPM as a function of surface separation, was used to determine the relative extension of the polyelectrolyte away from the interface. At low pH (3.2) and high ionic strength, the adsorbed polyelectrolyte molecules adopt a highly extended conformation; as the pH is increased (to 4.6 then to 5.5) the polymer chains collapse progressively towards the interface. Reversal of this pH cycle causes a re-protonation of the adsorbed polymers and highlights the finite timescale for this process to occur. The kinetics of this process was measured from the amount of trapped solvent within the polyelectrolyte layer as determined from the QCM-D. Upon decrease in pH, the adsorbed chains swell before partially collapsing. We propose that this is due to cross-linking of the polymer in the protonated state. Furthermore, the combination of techniques used in this study, namely optical reflectometry, CPM and QCM-D, allows the determination of the solvent content of the adsorbed film of polyelectrolyte as well as the extension of the polymer from the interface as a function of pH.
Keyword Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Chemistry
Physics
CHEMISTRY, PHYSICAL
PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Engineering, Architecture and Information Technology Publications
 
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