Electrochemical preparation and study of thin poly( N-vinylcarbazole) layers

Abstract

The growth of poly(N-vinylcarbazole) (PVCZ) films was followed under the conditions of potentiostatic square wave multipulse electropolymerization of N-vinylcarbazole in a medium of LiClO4 in acetonitrile. The time dependence of the polymer mass during the initial film growth and the changes in the oxidation level of PVCz during this process were derived from oscilloscopic I-t curves. Two polymerization stages were found: in the first, a thin layer of very compact (PVCZ) is formed, on which, in the second stage, a polymer with a globular structure grows. The thickness and morphology of the film is controlled by the frequency of the square wave potential pulses. The transition to the globular polymer is caused by polymerization via the vinyl groups of N-vinylcarbazole, initiated by H+ ions.Photogeneration of charge carriers was studied on non-conducting PVCz (polymerized only through the vinyl groups) formed in the bulk of a non-aqueous polymerization solution as a side product of electropolymerization. The intrinsic charge carrier photogeneration is depicted as a multistage process which can be described within the framework of the ballistic model. The dissociation of electron-hole pairs is in good agreement with predictions based on the Onsager theory of geminate recombination. The pair separation distance was determined as 2.8 nm.