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Issue 43, 2014
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Novel gigahertz frequency dielectric relaxations in chitosan films

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Abstract

Molecular relaxations of chitosan films have been investigated in the wide frequency range of 0.1 to 3 × 109 Hz from −10 °C to 110 °C using dielectric spectroscopy. For the first time, two high-frequency relaxation processes (in the range 108 to 3 × 109 Hz) are reported in addition to the low frequency relaxations α and β. These two relaxation processes are related to the vibrations of OH and NH2/NH3+, respectively. The high-frequency relaxations exhibit Arrhenius-type dependencies in the temperature range 10 °C to 54 °C with negative activation energy; this observation is traceable to hydrogen bonding reorientation. At temperatures above the glass transition temperature (54 °C), the activation energy changes from negative to positive values due to breaking of hydrogen bonding and water loss. Upon cooling in a sealed environment, the activation energies of two relaxation processes are nearly zero. FTIR and XRD analyses reveal associated structural changes upon heating and cooling. These two new high-frequency relaxation processes can be attributed to the interaction of bound water with OH and NH2/NH3+, respectively. A plausible scenario for these high-frequency relaxations is discussed in light of impedance spectroscopy, TGA, FTIR and XRD measurements.

Graphical abstract: Novel gigahertz frequency dielectric relaxations in chitosan films

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Publication details

The article was received on 14 Aug 2014, accepted on 29 Aug 2014 and first published on 29 Aug 2014


Article type: Paper
DOI: 10.1039/C4SM01804D
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Citation: Soft Matter, 2014,10, 8673-8684

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    Novel gigahertz frequency dielectric relaxations in chitosan films

    S. Kumar-Krishnan, E. Prokhorov, M. Ramírez, M. A. Hernandez-Landaverde, D. G. Zarate-Triviño, Y. Kovalenko, I. C. Sanchez, J. Méndez-Nonell and G. Luna-Bárcenas, Soft Matter, 2014, 10, 8673
    DOI: 10.1039/C4SM01804D

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