Block copolymer as a template for electrically conductive nanocomposites

Abstract

Electrically conductive nanocomposites were prepared by in situ polymerization of pyrrole in polystyrene-block-poly(n-butyl methacrylate) copolymer (PS-b-PnBMA) having lamellar microdomains, and characterized by using small angle X-ray scattering, transmission electron microscopy, and field emission scanning electron microscopy. For this purpose, the block copolymer film was immersed into a pyrrole - water mixture solution, followed by being immersed into FeCl3 - water solution. Since the pyrrole monomer was only partitioned into the PnBMA block, polypyrrole (Ppy) was only observed in PnBMA lamellar microdomains. The amount of Ppy in the block copolymer was varied by changing the immersion time of the block copolymer film into the pyrrole monomer solution. From the measured parallel and perpendicular conductivities of nanocomposites with various contents of Ppy by four-point and two-point probe techniques, respectively, the percolation threshold concentration of Ppy, above which nanocomposites behave as semiconductors, was very small (similar to 2 wt%). The low value of the percolation threshold was due to the formation of electrical paths resulting from the lamellar microdomains of the PS-b-PnBMA.