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Hysteresis in the surfactant-induced volume transition of hydrogels
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
2015 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 119, no 4, 1717-1725 p.Article in journal (Refereed) Published
Abstract [en]

The discontinuous uptake and release of surfactants by hydrogels and the accompanying discontinuous volume transition is known to occur with a hysteresis. We have performed a theoretical analysis in order to find the mechanistic origin of this phenomenon. Using a mean-field model, we have quantitatively reproduced the experimental behavior by considering the cost of elastically deforming the gel material to allow phase coexistence. The major part of the hysteresis is due to the high phase coexistence cost of the swelling transition, since in this direction the coexistence cost depends not only on the elasticity of the network (being a weak force in comparison) but also on the entropy of the monovalent nonsurfactant electrolyte present in the system.

Place, publisher, year, edition, pages
2015. Vol. 119, no 4, 1717-1725 p.
National Category
Physical Chemistry
URN: urn:nbn:se:uu:diva-188149DOI: 10.1021/jp5087416ISI: 000348753600047PubMedID: 25567724OAI: oai:DiVA.org:uu-188149DiVA: diva2:576404
Available from: 2012-12-12 Created: 2012-12-12 Last updated: 2016-04-27Bibliographically approved
In thesis
1. On the phase behaviour of hydrogels: A theory of macroion-induced core/shell equilibrium
Open this publication in new window or tab >>On the phase behaviour of hydrogels: A theory of macroion-induced core/shell equilibrium
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Colloidal macroions are known to interact very strongly with oppositely charged polyionic hydrogels. Sometimes this results in a non-uniform distribution of the macroions within the gel, a phenomenon that is not fully understood. This thesis is a summary of four papers on the development of a theory of the thermodynamics of macroions interacting with hydrogels, aimed at explaining the phenomenon of core/shell separation in spherical gels. It is the first theory of such interactions to use a rigorous approach to whole-gel mechanics, in which the elastic interplay between different parts of the gel is treated explicitly.

The thesis shows that conventional theories of elasticity, earlier used on gels in pure solvent, can be generalised to apply also to gels in complex fluids, and that the general features of the phase behaviour are the same if mapped to corresponding system variables. It is found that the emergence of shells is due to attractions between macroions in the gel, mediated by polyions. Since the shell state is unfavourable from the perspective of the shell itself, being deformed from its preferred state, there will be a hysteresis between the uptake and the release of the macroion, like already known to occur with the uptake and release of pure solvent.

Due to the elastic interplay, growth of the shell makes further growth progressively more favourable. Thus, unless there is a limited amount of macroions available the system will not reach equilibrium until complete phase transition has taken place. If the amount is limited the core/shell separation can be in equilibrium, so the volume of the solution that the gel is in contact with plays a very important part in determining the thermodynamic resting point of the system. The ability of a macroion/hydrogel to phase separate thus depends on the molecular properties whereas the ultimate fate of such a separation depends on the proportions in number between the ingoing components.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 70 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 169
polymer, polyelectrolyte, surfactant, thermodynamics, elasticity
National Category
Pharmaceutical Sciences Physical Chemistry
Research subject
Pharmaceutical Science
urn:nbn:se:uu:diva-188151 (URN)978-91-554-8565-8 (ISBN)
Public defence
2013-02-08, B42, BMC, Husargatan 3, Uppsala, 13:15 (English)
Available from: 2013-01-18 Created: 2012-12-12 Last updated: 2013-04-02Bibliographically approved

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Gernandt, JonasHansson, Per
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