title: The optimal structure-conductivity relation in epoxy-phthalocyanine nanocomposites.
abstract: Phthalcon-11 (aquocyanophthalocyaninatocobalt (III)) forms semiconducting nanocrystals that can be dispersed in epoxy coatings to obtain a semiconducting material with a low percolation threshold. We investigated the structure-conductivity relation in this composite and the deviation from its optimal realization by combining two techniques. The real parts of the electrical conductivity of a Phthalcon-11/epoxy coating and of Phthalcon-11 powder were measured by dielectric spectroscopy as a function of frequency and temperature. Conducting atomic force microscopy (C-AFM) was applied to quantify the conductivity through the coating locally along the surface. This combination gives an excellent tool to visualize the particle network. We found that a large fraction of the crystals is organized in conducting channels of fractal building blocks. In this picture, a low percolation threshold automatically leads to a conductivity that is much lower than that of the filler. Since the structure-conductivity relation for the found network is almost optimal, a drastic increase in the conductivity of the coating cannot be achieved by changing the particle network, but only by using a filler with a higher conductivity level.
authors.affiliation: Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands. L.J.Huijbregst@tue.nl
authors.forename: L J
authors.initials: LJ
authors.lastname: Huijbregts
authors.forename: H B
authors.initials: HB
authors.lastname: Brom
authors.forename: J C M
authors.initials: JC
authors.lastname: Brokken-Zijp
authors.forename: M
authors.initials: M
authors.lastname: Kemerink
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: M P de
authors.initials: MP
authors.lastname: Goeje
authors.forename: M
authors.initials: M
authors.lastname: Yuan
authors.forename: M A J
authors.initials: MA
authors.lastname: Michels