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Surface Grafted Chitosan Gels: Part II. Gel Formation and Characterization
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Tech Res Inst Sweden, Sweden.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
2014 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 29, 8878-8888 p.Article in journal (Refereed) Published
Abstract [en]

Responsive biomaterial hydrogels attract significant attention due to their biocompatibility and degradability. In order to make chitosan based gels, we first graft one layer of chitosan to silica, and then build a chitosan/poly(acrylic acid) multilayer using the layer-by-layer approach. After cross-linking the chitosan present in the polyelectrolyte multilayer, poly(acrylic acid) is partly removed by exposing the multilayer structure to a concentrated carbonate buffer solution at a high pH, leaving a surface-grafted cross-linked gel. Chemical cross-linking enhances the gel stability against detachment and decomposition. The chemical reaction between gluteraldehyde, the cross-linking agent, and chitosan was followed in situ using total internal reflection Raman (TIRR) spectroscopy, which provided a molecular insight into the complex reaction mechanism, as well as the means to quantify the cross-linking density. The amount of poly(acrylic acid) trapped inside the surface grafted films was found to decrease with decreasing cross-linking density, as confirmed in situ using TIRR, and ex situ by Fourier transform infrared (FTIR) measurements on dried films. The responsiveness of the chitosan-based gels with respect to pH changes was probed by quartz crystal microbalance with dissipation (QCM-D) and TIRR. Highly cross-linked gels show a small and fully reversible behavior when the solution pH is switched between pH 2.7 and 5.7. In contrast, low cross-linked gels are more responsive to pH changes, but the response is fully reversible only after the first exposure to the acidic solution, once an internal restructuring of the gel has taken place. Two distinct plc's for both chitosan and poly(acrylic acid), were determined for the cross-linked structure using TIRR. They are associated with populations of chargeable groups displaying either a bulk like dissociation behavior or forming ionic complexes inside the hydrogel film.

Place, publisher, year, edition, pages
2014. Vol. 30, no 29, 8878-8888 p.
Keyword [en]
Biocompatibility, Biological materials, Carboxylic acids, Chitosan, Crosslinking, Fourier transform infrared spectroscopy, Gels, Grafting (chemical), Hydrogels, Polyelectrolytes, Polyethylenes, Refractive index, Carbonate buffer solutions, Complex reaction mechanism, Crosslinked structures, Fourier transform infrared, Layer-by-layer approaches, Polyelectrolyte multilayer, Quartz crystal microbalance with dissipation, Total internal reflections
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-149983DOI: 10.1021/la501319rISI: 000339686700029ScopusID: 2-s2.0-84905041581OAI: diva2:742307
Swedish Research CouncilSwedish Foundation for Strategic Research

QC 20140901

Available from: 2014-09-01 Created: 2014-08-29 Last updated: 2014-09-01Bibliographically approved

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Liu, ChaoClaesson, Per M.Tyrode, Eric
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