Interactions between Alginate and Chitosan Biopolymers Characterised using FTIR and XPS
(2007) Interactions between Alginate and Chitosan Biopolymers Characterised using FTIR and XPS. Biomacromolecules 8(8):pp. 2533-2541.
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Abstract
This study investigates alginate-chitosan polyelectrolyte complexes (PECs) in the form of a film, a precipitate as well as in a layer-by-layer (LbL) assembly. The focus of this study is to fully characterise, using the complementary techniques of Fourier transform infrared (FTIR) spectroscopy and x-ray photoelectron spectroscopy (XPS) in combination with solution stability evaluation, the interactions between alginate and chitosan in the PECs. In the FTIR spectra, no significant change in band position of the two carbonyl vibrations from alginate occurs upon interaction with different ionic species. However, protonation of the carboxylate group causes a new band to appear at 1710 cm-1 as anticipated. Partial protonation of the amine group of chitosan causes the appearance of one new band (~1530 cm-1) due to one of the –NH3+ vibrational modes (the other mode overlaps with the amide I band). Importantly, the position of the two main bands in the spectral region of interest in partly protonated chitosan films is not dependent on the extent of protonation. XPS N 1s narrow scans can, however, be used to assess the degree of amine protonation. In our alginate-chitosan film, precipitate and LbL assembly, the bands observed in the FTIR correspond to the species –COO- and –NH3+ but their position is not different from each of the single components. Thus, the conclusion of the study is that FTIR cannot be used directly to identify the presence of PECs. However, in combination with XPS, both survey scans and narrow N 1s scans, a more complete description of the structure can be obtained. This conclusion challenges the assignment of FTIR spectra in the literature.
| Item Type: | Journal Article |
|---|---|
| Status: | Published |
| Keywords: | polyelectrolyte complex, infra red spectroscopy, x-ray photoelectron spectroscopy, layer-by-layer assembly, alginate, chitosan |
| Subjects: | 250000 Chemical Sciences > 250100 Physical Chemistry (incl. Structural) > 250103 Colloid and Surface Chemistry |
| ID Code: | 9408 |
| Deposited By: | Fredericks, Peter M |
| Deposited On: | 11 September 2007 |
| Alternative Locations: | http://dx.doi.org/10.1021/bm070014y |
| Copyright Owner: | Copyright 2007 American Chemical Society |
| Copyright Statement: | The contents of this journal can be freely accessed online via the ACS web page 12 months after publication. See link to ACS website. |
| Additional Information: | Self-archiving of the author-version is not yet supported by this publisher. For more information, please refer to the journal’s website (see hypertext link) or contact the author. |