Electrochemical studies of ferrocene and maleimide containing alternating copolymers Ahmed Alzharani, Charles Ault, Esam Allehyani, Chris S. Hance, Raymond B. Westby, Benjamin O. Tayo, Charles J. Neef ⁎ Department of Chemistry, Pittsburg State University, Pittsburg, KS 66762, USA abstract article info Article history: Received 14 July 2016 Received in revised form 9 January 2017 Accepted 10 January 2017 Available online 12 January 2017 Copolymers from vinylferrocene and 3-phenyl[5]ferrocenophane with N-ethyl and N-phenylmaleimide were electrochemically characterized. The deposition method of the polymer onto the electrode by oxidative deposi- tion or cast film was studied and showed that films produced by cast film exhibited a greater electrochemical re- sponse. The oxidation potentials of these materials were dependent on supporting electrolyte when using NaClO 4 , NaNO 3 or phosphate buffered saline, varying from 0.46 to 0.53 for oxidative deposited films and 0.35 to 0.43 V for cast films. Also, multiple redox waves were observed in the cyclic voltammograms of these materials at a pH of 1. Molecular modeling showed a low energy conformation with the ferrocenyl moiety in close proxim- ity to the maleimide. © 2017 Elsevier B.V. All rights reserved. Keywords: Ferrocenophane Maleimide Copolymer Electrochemistry 1. Introduction Redox active polymers have received considerable attention within the past 25 years. The potential applications of redox polymers include electrochemical sensors [1], batteries [2], biosensors [3], photovoltaics [4], and biofuel cells [5]. To meet the requirements of these applications, redox polymers must be electrochemically stable and possess a high de- gree of redox material. Within redox polymers, a variety of polymer backbones and redox active materials have been utilized to meet these requirements. Poly(vinylpyridine) [3], poly(N-vinylimidazole) [6], poly(allylamine) [7], and poly(ethylenimine) [8] are included in the polymers reported for support of the redox mediator. Among the most popular redox mediators reported include ferrocene [9], osmium [10], and ruthenium [11]. Ferrocene polymers have received considerable attention due to their well-behaved reversible oxidation and redox stability. Due to these properties, a renewed interest in ferrocene has been observed in recent literature [12]. Strained ferrocenophanes have been extensively studied and polymerized by ring opening polymerization [13]. The ver- satility of ferrocene polymers can be seen in the tunability of their elec- tronic, magnetic, and optical properties [14]. This tunability has also been observed pendant ferrocene polymers which change hydrophilic- ity upon oxidation [15]. With each approach, ferrocene has been shown to be an effective mediator for electron transfer and extremely versatile for a variety of applications. Although ferrocene polymers have been shown to be effective redox mediators, one of their limitations is low molecular weight, particularly in free radical polymerization. In addition to typical termination mech- anisms, ferrocene monomers have an additional termination mecha- nism. Ferrocene can transfer an electron to the radical at the end of the growing chain, creating a zwitterion and stopping polymerization. To circumvent this problem, we recently reported the synthesis of co- polymers from 3-phenyl[5]ferrocenophane-1,5-dimethylene or vinylferrocene with various N-substituted maleimides [16]. These co- polymers were high molecular weight and amorphous films could be solution cast from typical solvents such as THF or CHCl 3 . Initial electro- chemical studies on these materials revealed one oxidation potential. Compared to the ferrocenophane homopolymer [16] which showed two redox waves due to electronic communication between neighbor- ing ferrocenyl moieties, one oxidation potential for the copolymers indi- cated an alternating copolymer which isolates the ferrocenyl moieties. The cyclic voltammograms in CH 2 Cl 2 showed a greater I pc than I pa and I pa scaled linearly with the scan rate which is characteristic of adsorp- tion of the oxidized polymer to the electrode surface. In addition, oxida- tive electrodeposition from CH 2 Cl 2 gave films with good redox activity in an aqueous NaCl solution making these materials good candidates as chemically modified electrodes (CMEs). In this paper, we report the electrochemical characterization of co- polymers from vinylferrocene and 3-phenyl[5]ferrocenophane-1,5- dimethylene with N-ethyl and N-phenyl maleimide (Fig. 1). Previous results with these materials showed good electrochemical response in aqueous solutions, as well as, ease in preparation of the modified elec- trodes. In addition, the alternating distribution of the electron rich Journal of Electroanalytical Chemistry 786 (2017) 129–134 ⁎ Corresponding author. E-mail address: cneef@pittstate.edu (C.J. Neef). http://dx.doi.org/10.1016/j.jelechem.2017.01.024 1572-6657/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem