Interplay between structure and dynamics in chitosan films investigated with solid-state NMR, dynamic mechanical analysis, and X-ray diffraction

Carmiña Gartner, Betty Lucy López, Ligia Sierra, Robert Graf, Hans W. Spiess, Marianne Gaborieau

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Modern solid-state NMR techniques, combined with X-ray diffraction, revealed the molecular origin of the difference in mechanical properties of self-associated chitosan films. Films cast from acidic aqueous solutions were compared before and after neutralization, and the role of the counterion (acetate vs Cl⁻) was investigated. There is a competition between local structure and long-range order. Hydrogen bonding gives good mechanical strength to neutralized films, which lack long-range organization. The long-range structure is better defined in films cast from acidic solutions in which strong electrostatic interactions cause rotational distortion around the chitosan chains. Plasticization by acetate counterions enhances long-range molecular organization and film flexibility. In contrast, Cl⁻ counterions act as a defect and impair the long-range organization by immobilizing hydration water. Molecular motion and proton exchange are restricted, resulting in brittle films despite the high moisture content.
    Original languageEnglish
    Pages (from-to)1380-1386
    Number of pages7
    JournalBiomacromolecules
    Volume12
    Issue number4
    DOIs
    Publication statusPublished - 2011

    Keywords

    • acetic acid
    • chitosan
    • fatty acids
    • hydrogen bonding
    • long range order (solid state physics)
    • nuclear magnetic resonance spectroscopy

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