Electrical and physico-chemical properties of nanolayers of Conducting polyaniline-polystyrene or camphor sulfonic acid blends

Abstract

In this work we studied the physico-chemical and electrical properties of conducting blends of polyaniline (PANI) with polystyrene (PS) or camphor sulfonic acid (CSA) in an appropriate solvent such as m-cresol using various concentrations of PS. The thin films or nanolayers prepared by spin coating were analysed by ellipsometry (to measure the thickness), dynamic contact angle (to measure the surface energy), atomic force micropsopy techniques (to observe the topography and roughness of films), and by using a Keithley SMU 236 recorder under a vacuum of 10−3 mbar, to determine the variation of the current as a function of the voltage. Results obtained show that the variations of current I versus of the voltage V (from −15 V to +15 V) for all samples coated on silicon substrate indicate a barrier effect that becomes more and more important with the increase of the PS content, while samples prepared on a glass substrate give a linear variation of the current according to the voltage. These observations (load space limited current, Fowler-Nordheim tunneling effect, light-emitting diodes) will be described in this paper. The electrical conductivity of the PANI-CSA-PS blends at room temperature for different concentrations of polystyrene (from 0% to 50%) was measured by the four probe method as a function of the PANI weight fraction x. It seems that when x increases the electrical conductivity σ increases and reaches a threshold for x = 0.5 and σ = 8.5 S/cm.