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Issue 14, 2017
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Hydration-controlled anisotropic and giant permittivity in TEG-functionalized eumelanin

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Abstract

Although it has long been known that the peculiar electronic–ionic conductor behavior of eumelanin is critically dependent on hydration, the detailed mechanisms by which water–polymer interactions control and affect the conduction properties have remained largely obscure. In this paper, we report a remarkable anisotropy and giant polarization effect in a synthetic eumelanin (TEGMe) chemically functionalized with hydrophilic TEG residues. FT-IR analyses of water sorption isotherms and AC measurements were consistent with a microporous structure binding or hosting mainly isolated water molecules. In contrast, similar experiments on a commercial synthetic eumelanin (AMe) used as a reference were suggestive of a bulk macroporous scaffold binding or hosting liquid water. These data disclosed for the first time the differential impact on eumelanin conductivity of vapor, liquid and ice-like forms of water adsorbed onto or embedded into the polymer layer. It is thus demonstrated, for the first time, that hydration controls the conduction properties of eumelanin in a more complex manner than is commonly believed, involving, besides the reported semiquinone comproportionation equilibria, the mode of interaction of water molecules as governed by both the chemical and morphological features of the polymer.

Graphical abstract: Hydration-controlled anisotropic and giant permittivity in TEG-functionalized eumelanin

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Publication details

The article was received on 19 Dec 2016, accepted on 06 Mar 2017 and first published on 06 Mar 2017


Article type: Paper
DOI: 10.1039/C6CP08643H
Citation: Phys. Chem. Chem. Phys., 2017,19, 9432-9443
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    Hydration-controlled anisotropic and giant permittivity in TEG-functionalized eumelanin

    M. Ambrico, P. F. Ambrico, T. Ligonzo, A. Cardone, M. G. Bridelli, G. Casamassima, P. Manini and M. d'Ischia, Phys. Chem. Chem. Phys., 2017, 19, 9432
    DOI: 10.1039/C6CP08643H

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