Abstract
Polycarbazole and its derivatives have advantages of good environmental stability, electrochromic properties and photoconductivity which have attracted considerable attention because of their potential industrial applications in electroluminescent applications, rechargeable batteries, and light emitting diodes. They have the possibility of different position substitution (carbon C3-C3’ or N) that lead to different electropolymerization behaviours. However, the N position facilitates the grafting of various derivatives of interest and permits not to modify so much the radical cation formation during electropolymerization. In this paper, carbazole and its derivatives were electrochemically oxidized in acetonitrile solutions leading to the formation of thin polymer films. The morphological features and electrochemical properties of the as-formed polymer films were investigated in detail. Thanks to these experiments, the influence of the substitution on the properties of the polymer films was evidenced and discussed. In addition, fast electrochemistry experiments were carried out on platinum microelectrodes within 50-1000 V/s scan speed range. Reactivity of carbazole derivatives radical cations and dimers was investigated through these experiments. Thermodynamic and kinetic information (e.g. redox standard potential, heterogeneous and dimerization rate constants) was extracted after coupling with electrochemical simulations.
Highlights
The discovery of organic conducting polymers in Shirakawa’s laboratory in the early 1970s and the demonstration by MacDiarmid et al of the semiconducting properties of polyacetylene (Shirakawa et al, 1977) paved the way for an intense research activity on these materials to exploit these conducting properties
Influence of the Solvent and Carbazole Concentration The oxidation of 10−2 M carbazole was performed by cyclic voltammetry (CV) at Pt electrodes in 0.1 M LiClO4 in acetonitrile (ACN) or dimethylformamide (DMF) solutions (Figure 1)
The redox process of polycarbazole is observed in ACN since a polyCz oxidation peak and a polyCz reduction peak are clearly distinguishable at +0.8 and +0.7 V/Saturated Calomel Electrode (SCE), respectively
Summary
The discovery of organic conducting polymers in Shirakawa’s laboratory in the early 1970s and the demonstration by MacDiarmid et al of the semiconducting properties of polyacetylene (Shirakawa et al, 1977) paved the way for an intense research activity on these materials to exploit these conducting properties. Various methods have been used in the past for growing such conducting polymers including chemical oxidation (Huang et al, 2012), plasma polymerization (Yaguee et al, 2008), LangmuirBlodgett technique (Park et al, 2003), or electrochemistry (Fonseca et al, 2017). Among these methods, electrochemical deposition is the most convenient and reliable method for growing conducting polymer thin films with controlled properties. Carbazole is one of the aromatic heterocyclic organic compounds that could lead to the formation of a conducting polymer film by oxidation. Resulting carbazole-based conjugated polymer films can be used as components of sensors (Joshi et al, 2014; Vedarajan et al, 2014), batteries (Saraswathi et al, 1999), OLED (Grigalevicius et al, 2011; Srivastava and Chakrabarti, 2015), or electrochromic devices (Hu et al, 2013; Hsiao and Lin, 2016), mainly because of their electron-donating nature, high photoconductivity and strong fluorescence
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