The methods of synthesis and the properties of polyaniline—a representative of the family of conducting polymers—are reviewed briefly. It is shown that variation in the conditions of aniline polymerization makes it possible to synthesize polymer materials with the desired structures and properties and, thus, to provide for the use of polyaniline in various fields of science and engineering. Special attention is given to the matrix synthesis of polyaniline as the main approach to obtain electroactive and conducting composite materials. The use of polyaniline and the related composite materials in polymer electronics is analyzed briefly.

We report here the one-step electrochemical synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) in an aqueous dispersion of reduced graphene oxide (rGO). The electrochemical polymerization is carried out at 1.05 V in aqueous media in the presence of 10⁻² M 3,4-ethylenedioxythiophene and 1 g L⁻¹ rGO. Unlike composites of PEDOT and graphene oxide or poly(styrene sulfonate) which have rather smooth and non-porous surface morphologies, the scanning electron microscopy images reveal that the PEDOT composite films obtained in this work have uniformly porous and open surface morphology. X-ray photoelectron spectroscopy (XPS) showed that rGO had initially a low concentration of oxygen-containing surface groups (C : O ratio = 6.5), but both FTIR spectroscopy and XPS showed that the electropolymerization resulted in the formation of OH groups in the composite film. Characterization with cyclic voltammetry and electrochemical impedance spectroscopy demonstrates that the composite films behave almost like ideal capacitors having an areal capacitance of 12.2 mF cm⁻². The composite films had a very good potential cycling stability in 0.1 M KCl with only 12.4% degradation of the capacitance in a three-electrode cell after 3000 cycles between −0.5 and 0.5 V. The degradation was higher (32.8%) in the broader potential range of −0.8 and 0.7 V.

Herein, we report the incorporation of a 10 μm thick reduced graphene oxide (RGO) barrier layer in a plasticized poly(vinyl chloride) (PVC) film as the main constituent in ion-selective membranes used in potentiometric solid-contact ion-selective electrodes (SCISE). Fourier transform infrared attenuated total reflection (FTIR-ATR) and oxygen transmission rate (OTR) measurements showed that the embedded RGO barrier efficiently impedes the diffusion of liquid water, carbon dioxide and oxygen (O₂) through the 400 μm thick PVC film, which causes potential instability and irreproducibility of the SCISEs. The measurements revealed that the RGO layer completely blocks the carbon dioxide diffusion, while it fully blocks the water diffusion for 16 h and reduced the OTR by 85% on average. The μm-thick RGO films used in this study were easier to handle and incorporate into host polymers, and form more efficient and robust barriers compared to the mono-, few- and multilayer graphene commonly applied as barrier layers for liquids and gases. We also demonstrated that the FTIR-ATR technique employed in the permeability measurements is a versatile and very sensitive technique for studying the diffusion of small amounts of water and carbon dioxide through graphene-based thin films.

We report here the in situ polymerization of aniline in the presence of exfoliated graphite of two different grades (graphene and graphite) resulting in composite materials which are readily dispersible in N-methylpyrrolidone. Compared to polyaniline (PANI) prepared without graphene/graphite which becomes electrically non-conducting at pH > 3, the PANI–graphene/graphite composites showed significantly improved pH stability and electrochemical behaviour in aqueous electrolyte solutions at pH ≤ 8, without any further need of surface functionalization of the graphene/graphite flakes to stabilize the conducting form of polyaniline (PANI). The improved electroactivity is ascribed to the synergistic effect of graphene/graphite and PANI, and the network formation of the electrically conducting exfoliated graphites in the PANI matrix, which was electrochemically confirmed by simple cyclic voltammetric measurements at pH = 9.5 in the presence of the Ru(NH₃)₆ ^2+/3+ and Fe(CN)₆ ^3−/4− redox couples. Due to the dispersibility of the composites, thin films possessing stability in water can easily be prepared by solution casting for different types of solid-state chemical sensor and ion-selective electrode applications operating at neutral pH. By using sodium ascorbate as a model substance, we show that its amperometric detection at pH = 7.3 with the PANI–graphite films results in a current amplification of 1.3–10.2 times in the concentration range of 10⁻⁴–10⁻² M, compared to conventional PANI, which clearly demonstrates the advantage of incorporating exfoliated graphites in the PANI films. The materials reported in this paper were systematically characterized with cyclic voltammetry, FTIR, Raman and X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction and electrical conductivity measurements.

Electrically conductive composite nanofibers were fabricated using poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) and cellulose nanofibrils (CNFs) via the electrospinning technique. Poly(ethylene oxide) (PEO) was used to assist the electrospinning process, and poly(ethylene glycol) diglycidyl ether was used to induce chemical cross-linking, enabling stability of the formed fibrous mats in water. The experimental parameters regarding the electrospinning polymer dispersion and electrospinning process were carefully studied to achieve a reproducible method to obtain bead-free nanofibrous mats with high stability after water contact, with an electrical conductivity of 13 ± 5 S m^–1, thus making them suitable for bioelectrochemical applications. The morphology of the electrospun nanofibers was characterized by scanning electron microscopy, and the C/S ratio was determined with energy dispersive X-ray analysis. Cyclic voltammetric studies showed that the PEDOT–PSS/CNF/PEO composite fibers exhibited high electroactivity and high stability in water for at least two months. By infrared spectroscopy, the slightly modified fiber morphology after water contact was demonstrated to be due to dissolution of some part of the PEO in the fiber structure. The biocompatibility of the PEDOT–PSS/CNF/PEO composite fibers when used as an electroconductive substrate to immobilize microalgae and cyanobacteria in a photosynthetic bioelectrochemical cell was also demonstrated.