Dielectric studies on charge hopping in melanin polymer

Dielectric spectroscopy in the frequency 10(-2) - 10(7) Hz and temperature 253-393 K ranges has been used in order to examine polarization effects and charge carrier motion in synthetic dopa-melanin with relation to the molecular structure of the polymer. Charge hopping process is postulated to be the main mechanism involved in the dielectric response of melanin at low frequencies. Two relaxation regions attributed to the water-dependent hopping polarization have been found. According to the spatial model of the molecular arrangement in melanin, two main hopping distances, similar to1.5 and similar to3.6 nm have been estimated. Changes in the hydration state of melanin upon heating cause an increase in hopping distances. (C) 2002 Elsevier Science B.V. All rights reserved.