On the mechanism of electrical conduction in thin films of some polysulfone-poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers

Polysulfone poly(alkylene oxide)-poly(dimethylsiloxane) block copolymers have been prepared by the hydrosilylation reaction of allyl endcapped poly[(ethylene oxide) (propylene oxide)] oligomers with Si-H terminated polydimethylsiloxane in chlorobenzene using an isopropanol solution of hexachloroplatinic (IV) acid as catalyst for hydrosilylation. The temperature dependences of electrical conductivity and thermoelectric power (Seebeck coefficient) of copolymers were studied using thin-film samples deposited from dimethylformamide (spin coating technique) onto glass substrates. Organic films with reproducible electronic transport and optical properties can be obtained if, after deposition, they are submitted to a heat treatment consisting of several successive heating/cooling cycles within temperature range of (295-485) K. Investigated copolymers presents typical semiconducting characteristics. The values of some fundamental parameters (activation energy of electrical conduction, ratio of carrier mobilities, optical energy bandgap) have been determined. The mechanisms of electronic transport are identified in different temperature domains. Transmission and absorption spectra have been recorded and optical energy bandgaps are calculated from the absorption spectra. The thermistor effect of investigated copolymers is also discussed. (C) 2013 Elsevier Ltd. All rights reserved.