Probing the interactions in composite of graphene oxide and polyazulene in ionic liquid by in situ spectroelectrochemistry Milla Suominen a, b, * , Pia Damlin b, ** , Carita Kvarnstr € om b a Turku University Graduate School (UTUGS), Doctoral Programme in Physical and Chemical Sciences, Finland b Turku University Centre for Materials and Surfaces (MatSurf), Laboratory of Materials Chemistry and Chemical Analysis, University of Turku, FIN-20014 Turku, Finland article info Article history: Received 29 May 2018 Received in revised form 29 June 2018 Accepted 12 July 2018 Available online 17 July 2018 Keywords: Polyazulene Graphene oxide Composite Ionic liquid In situ spectroelectrochemistry abstract Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically deposited from a choline based ionic liquid (IL), and characterized with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using Kretschmann geometry, and UVeVis spec- troscopy during electropolymerization and electrochemical oxidation. The use of different ILs has been shown to affect the morphology and long term cycling stability of PAz while fabricating composites is known to sometimes dramatically affect the electronic properties of PAz. The aim of this work was to study how the use of a viscous IL and, furthermore, incorporating GO affected the structural, electronic and optical properties of PAz. Overall, the vibrational behavior of the composite was very similar to PAz. During positive doping, the doping-induced infrared active vibrations (IRAV) of the composite were found at higher wavenumbers indicating shorter conjugation of PAz in the composite. Comparison to previous works and to PAz electropolymerized from conventional organic electrolyte solution revealed that polymerization in the viscous IL leads to electroactive and stable PAz with shorter effective conjugation length. The correlation between IRAV bands of doped PAz and Raman bands of neutral materials are also discussed within the framework of effective conjugation coordinate model (ECC). © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Azulene, isomer of naphthalene, is a non-alternant and non- benzenoid aromatic hydrocarbon utilized in various organic elec- tronics, such as organic photovoltaics [1,2], nonlinear optical ma- terials (NLO) [3], organic field effect transistors (OFETS) [4], and electrochromic applications [5]. Azulene monomer (Scheme 1) consists of a five-membered ring and a seven-membered ring fused together. Since the five-membered ring is electron rich while the seven-membered ring is electron poor, an unusually large dipole moment is produced (1.08 D) [6]. This polarizability of azulene and its derivatives leads to unique optical and electronic properties that can be applied in many aspects of organic electronics [7]. Azulene can be polymerized upon anodic oxidation by chemical and elec- trochemical route to polyazulene (PAz). The chemical polymerization requires hazardous chemicals and results in rather low conductivity (1.22 S/cm) [8], while the electropolymerization of azulene occurs at low potentials and results in films with slightly higher conductivity (2.2 S/cm) [9]. PAz has been electro- polymerized in organic solvents [10e14] and ionic liquids (ILs) [15e17], and it has also been copolymerized with different thio- phenes [18,19]. The best quality PAz films are obtained in non-polar or only moderately polar solvents [11], and the use of ILs produces PAz films with higher capacity due to the formation of longer effective conjugation length [15,16], improved cycling stability [17], and uniform morphology [15,17]. The charge transport in PAz has been the subject of vigorous studies, both in conventional solvents and in ILs [16,20e24]. Charge is mainly transported in electronically conducting polymers (ECPs) with a nondegenerate ground state by the well-established radical cations and dications: polarons, polaron pairs and bipolarons [25]. These are additional energy states formed in the band gap region upon doping, and are accompanied by changes in the conformation of the polymer chain. A group of methods, that effectively probe the optical and electronic properties and the structural changes taking place during the doping process, is in situ spectroelectrochemistry * Corresponding author. Turku University Graduate School (UTUGS), Doctoral Programme in Physical and Chemical Sciences, Finland. ** Corresponding author. E-mail addresses: milsuo@utu.fi (M. Suominen), pia.damlin@utu.fi (P. Damlin). Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta https://doi.org/10.1016/j.electacta.2018.07.069 0013-4686/© 2018 Elsevier Ltd. All rights reserved. Electrochimica Acta 284 (2018) 168e176