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Deswelling Kinetics of Polyacrylate Gels in Solutions of Cetyltrimethylammonium Bromide
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.ORCID iD: 0000-0002-0895-1180
2007 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 33, 9770-9778 p.Article in journal (Refereed) Published
Abstract [en]

The deswelling kinetics of single sodium polyacrylate gel beads (radius 40−160 μm) in aqueous solutions of cetyltrimethylammonium bromide under conditions of forced convection are investigated using micromanipulator assisted light microscopy. The purpose of the study is to further evaluate a previously published model (J. Phys. Chem. B 2003, 107, 9203) using a higher homolog surfactant. For gels with expected fast deswelling (small gel size/low surfactant concentration) and/or in low electrolyte concentration, the model is found to correctly predict the deswelling characteristics of the gel beads. However, for some gels with expected slow deswelling, especially in high electrolyte concentration (10 mM NaBr), the model widely underestimates the required deswelling time. The reason for this is argued to be the longer time frame and high bromide concentration allowing the formation of a denser, more ordered structure in the surface phase, which resists the deformation and reorganization of material necessary for deswelling. Unexpectedly long lag times before the start of deswelling are also found for gels in low surfactant concentration, indicating that a relatively high surfactant concentration in the gel, greatly exceeding the critical aggregation concentration, is needed to start formation of a collapsed surface phase. This critical surfactant concentration is found to be dependent on initial gel radius, as small gels require a relatively higher concentration to initiate collapse.

Place, publisher, year, edition, pages
2007. Vol. 111, no 33, 9770-9778 p.
National Category
Pharmaceutical Sciences
URN: urn:nbn:se:uu:diva-96225DOI: 10.1021/jp0728151ISI: 000248759000012PubMedID: 17655349OAI: oai:DiVA.org:uu-96225DiVA: diva2:170726
Available from: 2007-09-27 Created: 2007-09-27 Last updated: 2016-04-27Bibliographically approved
In thesis
1. Interaction between Crosslinked Polyelectrolyte Gels and Oppositely Charged Surfactants
Open this publication in new window or tab >>Interaction between Crosslinked Polyelectrolyte Gels and Oppositely Charged Surfactants
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interactions between anionic, crosslinked gels and cationic surfactants have been investigated. When exposed to oppositely charged surfactant, the gel collapses into a dense complex of polyion and micelles. During deswelling, the gel phase separates into a micelle-rich, collapsed surface phase, and a swollen, micelle-free core, both still part of the same network. As more surfactant is absorbed, the surface phase grows at the expense of the core, until the entire gel has collapsed. Polyacrylate (PA) gels with dodecyl- (C12TAB), and cetyltrimethylammonium bromide (C16TAB), as well as hyaluronate gels with cetylpyridinium chloride, have been studied.

Kinetic experiments have been performed on macro- as well as microgels, using micromanipulator assisted light microscopy for the latter. A surfactant diffusion controlled deswelling model has been employed to describe the deswelling. The deswelling kinetics of PA microgels have been shown to be controlled by surfactant diffusion through the stagnant layer surrounding the gel, as the surface phase is relatively thin for the major part of the deswelling. For macroscopic PA gels the surface phase is thicker, and the kinetics with C12TAB were therefore also influenced by diffusion through the surface phase, while for C16TAB they were dominated by it.

Relevant parameters have also been determined using equilibrium experiments. An irregular, balloon-forming deswelling pattern, mainly found for macrogels, as well as unexpectedly long lag times and slow deswelling for microgels, are reported and discussed.

The microstructure of fully collapsed PA/C12TAB complexes has been studied using small-angle X-ray scattering. A cubic Pm3n structure was found at low salt concentration, which melted into a disordered micellar phase as the salt concentration was increased. Further increasing the salt concentration dissolved the micelles, resulting in no ordering.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 68 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 62
Pharmaceutical chemistry, gel, polyelectrolyte, surfactant, deswelling, kinetics, phase separation, volume transition, ion-exchange, diffusion, liquid crystal, SAXS, cubic Pm3n, Farmaceutisk kemi
urn:nbn:se:uu:diva-8216 (URN)978-91-554-6970-2 (ISBN)
Public defence
2007-10-19, B22, BMC, Husargatan 3, Uppsala, 09:15
Available from: 2007-09-27 Created: 2007-09-27Bibliographically approved

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