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Hydration-controlled anisotropic and giant permittivity in TEG-functionalized eumelanin
Marianna Ambrico1, Paolo F Ambrico1, Teresa Ligonzo2
1CNR-Istituto di Nanotecnologia Via Amendola 122/D, I-70126 Bari, Italy. marianna.ambrico@cnr.it.
Physical Chemistry Chemical Physics : PCCP
|March 24, 2017
Summary
This study reveals how water interacts with eumelanin, impacting its conductivity. Different water forms (vapor, liquid, ice) affect conduction differently based on the polymer's structure and chemistry.
Area of Science:
- Materials Science
- Biophysics
- Polymer Chemistry
Background:
- Eumelanin's electronic-ionic conductor behavior is known to depend on hydration.
- The precise mechanisms of water-polymer interactions influencing eumelanin conductivity remain poorly understood.
Purpose of the Study:
- To investigate the detailed mechanisms of water-polymer interactions affecting eumelanin conduction.
- To explore the role of different water forms (vapor, liquid, ice) on eumelanin conductivity.
- To report anisotropy and giant polarization effects in functionalized synthetic eumelanin.
Main Methods:
- Fourier Transform Infrared (FT-IR) spectroscopy for water sorption isotherms.
- AC measurements to assess electrical conductivity.
- Comparison of a functionalized synthetic eumelanin (TEGMe) with a commercial synthetic eumelanin (AMe).
Main Results:
- TEGMe exhibited a microporous structure hosting isolated water molecules, leading to anisotropy and giant polarization.
- AMe displayed a macroporous structure hosting liquid water.
- Demonstrated the differential impact of water's vapor, liquid, and ice-like forms on eumelanin conductivity.
Conclusions:
- Hydration controls eumelanin conductivity in a complex manner, beyond semiquinone equilibria.
- The mode of water molecule interaction, dictated by polymer chemistry and morphology, is crucial.
- This work provides novel insights into water-eumelanin interactions and their influence on conductive properties.
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