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Core-shell separation of a hydrogel in a large solution of proteins
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
2012 (English)In: Soft Matter, ISSN 1744-683X, Vol. 8, no 42, 10905-10913 p.Article in journal (Refereed) Published
Abstract [en]

Upon absorption of large oppositely charged electrolytes such as proteins, polyionic hydrogels are frequently observed to separate into dense shell–swollen core states. We have developed a theory that in a detailed way takes into account the inhomogeneous swelling and distribution of the protein within such a core–shell separated gel. With this we investigated whether the core–shell separation can be an equilibrium state or if it must be understood as a dynamical phenomenon. Restricting ourselves to spherical gels with an unlimited supply of protein, we found that as an intermediate between a swollen and a collapsed gel the core–shell state can indeed be the one of lowest free energy but this state is not stable. In such cases where formation of a shell could occur spontaneously there was no further thermodynamic barrier to complete collapse of the gel (but possibly dynamical ones). The core–shell separation was favourable in systems of high charge and low ionic strength and was explained, within our theory, by the fact that the energy gain in packing proteins and polyions closely together outweighs the entropy loss of the uneven distribution.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2012. Vol. 8, no 42, 10905-10913 p.
National Category
Physical Chemistry
URN: urn:nbn:se:uu:diva-184518DOI: 10.1039/C2SM26227DISI: 000310829400014OAI: oai:DiVA.org:uu-184518DiVA: diva2:565674
Available from: 2012-11-08 Created: 2012-11-08 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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