Electroactive films based on conducting polymers have numerous potential applications, but practical devices frequently require a combination of properties not met by a single component. This has prompted extension to composite materials, notably those in which particulates are immobilised within a polymer film. Irrespective of the polymer and the intended application, film wetting is important: by various means, it facilitates transport processes -of electronic charge, charge-balancing counter ions ("dopant") and analyte/reactant molecules -and motion of polymer segments. While film solvent content and transfer have been widely studied for pristine polymer films exposed to molecular solvents, extension to non-conventional solvents (such as ionic liquids) or to composite films has been given much less attention. Here we consider such cases, based on polyaniline films. We explore two factors: the nature of the electrolyte (solvent and filmpermeating ions) and the effect of introducing particulate species into the film. In the first instance, we compare film behaviours when exposed to a conventional protic solvent (water) with an aprotic ionic liquid (Ethaline) and the intermediate case of a protic ionic liquid (Oxaline). Secondly, we explore the effect of inclusion of physically diverse particulates: multi-walled carbon nanotubes, graphite or molybdenum dioxide. We use electrochemistry to control and monitor film redox state and change therein, and acoustic wave measurements to diagnose rheologically vs. gravimetrically determined response.The outcomes provide insights of relevance to future practical applications, including charge/discharge rates and cycle life for energy storage devices, "salt" transfer in water purification technologies, and the extent of film "memory" of previous environment when sequentially exposed to different media. 11,20 (including supercapacitors 21 ) and artificial muscles 22,23 . Inevitably, such applications require combinations of properties that are not generally found in a single material, so it is natural to move to composites. Additionally, it has become widely recognized that dynamics within such systems -from transport rates of charge balancing ions and analyte species to the nanomechanical motions of the polymer chains -are governed by the solvent content, i.e. the internal wettability of the material. In this study, we bring these two aspects together by exploring solvation phenomena for polyaniline composites containing multi-walled carbon nanotubes (MWCNTs), molybdenum dioxide and/or graphite when exposed to aqueous and room temperature ionic liquid media. KeywordsPolyaromatic conducting polymers, typified by polyaniline, may be interconverted between their insulating and conducting forms by electrochemically controllable redox processes 1,24 . Electron transfer at the electrode/polymer interface creates positive charge sites, for which electroneutrality requires the entry of anions (or exit of cations) at the polymer/solution interface 25 (colloquially, "(un-)doping"). T...

Although the World Health Organization (WHO) recommends a limit of 1.5 mg l−1 fluoride ions in drinking water, this is not satisfied in many parts of the world. When this limit is exceeded, the electrochemically switched ion-exchange (ESIX) technique (mainly based on conductive polymers) has been identified as a promising method for removing the excess fluoride ions. The present study aimed to develop an efficient method based on the ESIX technique by using poly(aniline-co-o-aminophenol) copolymer to extract fluoride ions. Electrochemical quartz crystal microbalance (EQCM) and acoustic admittance data were utilized to assay the synthetic efficiency of copolymer deposition, and to evaluate the dependence of the defluoridation process on the proportions of the monomers in the copolymer matrix and on film thickness. The resulting films were characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electrochemical microscopy (SEM) techniques. For optimized co-monomer ratio in the feedstock, poly(aniline-co-o-aminophenol) at an applied potential of 0.30 V showed excellent performance for fluoride removal from water at pH 6.6, to the extent of 20 (mg F−) (g polymer)−1. Comparison of the performance of ESIX using poly(aniline-co-o-aminophenol) with that of other techniques and materials reveal that it has significant potential for water defluoridation.

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