Interactions between Alginate and Chitosan Biopolymers Characterised using FTIR and XPS

Lawrie, Gwen, Keen, Imelda, Chandler-Temple, Adrienne F., Rintoul, Llew, Fredericks, Peter M., Drew, Barry, & Grondahl, Lisbeth (2007) Interactions between Alginate and Chitosan Biopolymers Characterised using FTIR and XPS. Biomacromolecules, 8(8), pp. 2533-2541.

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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.

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ID Code: 9408
Item Type: Journal Article
Refereed: Yes
Additional Information: This article is freely available from the American Chemical Society website 12 months after the publication date. See links to publisher website in this record.
Keywords: polyelectrolyte complex, infra red spectroscopy, x, ray photoelectron spectroscopy, layer, by, layer assembly, alginate, chitosan
DOI: 10.1021/bm070014y
ISSN: 1526-4602
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Colloid and Surface Chemistry (030603)
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
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.
Deposited On: 11 Sep 2007 00:00
Last Modified: 25 Feb 2013 03:51

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