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Mesoporous Hydrogels: Revealing Reversible Porosity by Cryoporometry,X-ray Scattering, and Gas Adsorption
Max Planck Institute of Colloids and Interfaces, Department of Colloid Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). (Material chemistry)
2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 12, 10158-10164 p.Article in journal (Refereed) Published
Abstract [en]

Mesoporous poly(2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) networks, with cross-linkercontents ranging from 100 to 5 mol %, were prepared using a hard-templating approach. The imbibition of the silicapellets with a monomer/cross-linker mixture resulted in mesoporous gels with a pore size of ~10 nm, which correspondswell with the average size of the fumed silica particles (10-11 nm). The highly cross-linked materials showed permanentsurface areas of up to 230m2 g-1 and porosities up to ~33 vol %. The porosity of the hydrogels was investigated in bothdry and water-saturated state by nitrogen sorption, cryoporometry, and small-angle X-ray scattering (SAXS). It is onlypolymeric materials that contain 50 mol % or more of the cross-linker that showed a significant porosity afterevaporative drying. Freeze-drying is able to preserve the porosity also for hydrogels of intermediate cross-linker content,but the pores of the materials of low cross-linker content collapses completely upon solvent removal. The observedcritical cross-linker ratio for pore stability compared favorably with a simple estimate of the critical cross-linker densityneeded to make the material sufficiently stiff to withstand the Laplace pressure during solvent removal. Analysis of thehydrogels in the water swollen state revealed that gels having cross-linker contents down to 5 mol % still possessedmesoporosity. The pores got less defined at very low cross-linker contents, while their size was rather constant atintermediate to high cross-linking densities. Closed pores could be reopened upon swelling, which suggests that theobserved pore collapse upon drying may be at least partly reversible.

Place, publisher, year, edition, pages
Washington, DC: American Chemical Society , 2010. Vol. 26, no 12, 10158-10164 p.
Keyword [en]
Mesoporous Hydrogels, Cryoporometry
National Category
Inorganic Chemistry
Research subject
Materials Chemistry
URN: urn:nbn:se:su:diva-46201DOI: 10.1021/la100290jOAI: diva2:372047
Available from: 2010-11-26 Created: 2010-11-23 Last updated: 2010-12-13Bibliographically approved

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Bergström, Lennart
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