The use of conducting polymers as coating layers for the protection of surfaces against corrosion represents an important topic for investigation, as reported in the literature. In this work, polypyrrole/Fe3O4 nanoparticles (Fe3O4_NPs/PPy) hybrid nanocomposites (HN) were incorporated as anticorrosive additives in an epoxy paint to protect SAE 1010 carbon steel from corrosion. The HN particles were obtained by chemical polymerization of pyrrole in an aqueous solution in the presence of Fe3O4_NPs and were characterized by infrared absorption spectrophotometry, dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM). The electrochemical impedance spectroscopy (EIS) was used in the analysis of the electrochemical response of the coated surface with and without HN. DLS data showed that the Fe3O4_NPs and Fe3O4_NPs/PPy obtained in solution present average diameters of (19.7 ± 9.6) nm and (63.5 ± 27.7) nm, respectively. TEM images showed Fe3O4_NPs with smaller sizes (10 nm - 30 nm), and that the HN had diameters smaller than 100 nm, consisting of Fe3O4 cores coated with polypyrrole. EIS measurements have shown that the addition of HN to the epoxy paint could improve the efficiency of the anticorrosive coating when compared to the original epoxy paint prepared without any corrosion inhibitor.

The production of conductive and organic devices from a 3D printer represents a promising strategy for several areas. In particular, the synthesis of polypyrrole-coated acrylonitrile butadiene styrene (ABS) composites can be considered an important step to produce conductive supports for 3D printing. Herein, it is reported the production of ABS samples through the additive manufacturing process (3D printing) accordingly to the Fused Deposition Modeling (FDM) method. The hydrophilic behavior was controlled by the surface treatment using air plasma for the following step of coating with polypyrrole (PPy) via an in situ polymerization, using two different oxidants: ferric chloride (FeCl3.6H2O) and ammonium persulfate (APS). The chemical, optical, surface, and electrical properties of these materials were characterized through Fourier Transform infrared spectroscopy (FTIR), contact angle measurements, cyclic voltammetry, Scanning Electron Microscopy (SEM), 4-probe electrical measurement, and mechanical tensile testing. The ABS/PPy (FeCl3) composite exhibited a low electrical contact resistance and better performance for applications that require electrodes with a good conductance level.

Dielectric characterization has been applied as a convenient tool for evaluation of transport and polarization mechanisms in soft materials. In this work, we have explored the study of charge transport mechanisms in alginate hydrogel containing neomycin-loaded liposomes. For comparison, drug release kinetic was evaluated by using UV-Vis spectrophotometry and electrical impedance spectroscopy (EIS) at different external direct current (DC) polarization (100 mV and 1 V). The charge transfer resistance (Rct) was proportional to DC electrical stimulation and inversely to the amount of released neomycin. Optical and electrical measurements confirmed the dependence of neomycin release under influence of electrical potentials. The kinetic profile of these systems was described by zero-order model. In addition, the Korsmeyer-Peppas model also suggested a diffusion mechanism based on super case II transport (non-Fickian). These results encouraged the use of EIS as a “dark" spectroscopy technique, since EIS is effective for studies of release kinetics controlled by DC external electrical excitation.

The development of organic devices based on conducting polymers for biofilm detection requires the combination of superior electrical response and high surface area for biofilm incorporation. Polypyrrole is a potential candidate for application in biofilm detection and control due to its characteristic superior electrical response and strong interaction with bacteria, which enables the use of the bioelectric effect in resulting devices. In this study, chemically synthesized polypyrrole was applied as a support for biofilm growth of S. aureus. Modifications in the electrical response of the polymeric template were explored to identify general mechanisms established during the deposition of the biofilm.

Large scale preparation of hybrid electrical actuators represents an important step for the production of low cost devices. Interfacial polymerization of polypyrrole in the presence of multi-walled carbon nanotubes represents a simple technique in which strong interaction between components is established, providing composite materials with potential applications as actuators due to the synergistic interaction between the individual components, i.e., fast response of carbon nanotubes, high strain of polypyrrole, and diversity in the available geometry of resulting samples.

Compósitos de poli(álcool vinílico)/dióxido de titânio preparados pela técnica de eletrofiação são potenciais candidatos para aplicações nas quais grande absorbância na região do ultra-violeta e transparência na região do visível são requeridas. A incorporação de semicondutor nas fibras pode ser inferida pela redução da impedância elétrica das fibras fabricadas por eletrofiação, como consequência do aumento na densidade de grãos de semicondutor dispersos nas fibras poliméricas. As propriedades térmicas do compósito polímero/semicondutor são dominadas pela resposta do PVA sendo a influência do dióxido de titânio detectada no espectro de absorção de luz pela maximização da absorbância na faixa de 240 nm a 400 nm. Os resultados indicam que o compósito de PVA/TiO2 pode ser convenientemente aplicado como curativo com proteção adicional contra efeitos de radiação ultravioleta (UVA e UVB) na pele humana. Uma aplicação adicional para o compósito PVA/TiO2 foi abordada com o estudo dos processos fotocatalíticos na degradação da rodamina B.

Electrospun composites of polyvinyl alcohol/titanium dioxide are potential candidates for applications that require high level of absorbance in the UV and transparency in the visible region. The incorporation of semiconductor particles in the core of fibers can be inferred from the reduction in the electrical impedance of electrospun fibers, as a consequence of the increased density of semiconductor granules along the fiber. The thermal properties of PVA dominate in the complete response of the composite while the influence from titanium dioxide is noted with an increased absorption from 240 nm to 400 nm. The results indicate that the PVA/TiO2 composites can be applied as wound dressing with additional protection against effects of ultraviolet radiation (UVA and UVB) on human skin. An additional application studied here was based on the use of PVA/TiO2 nanocomposites as active agent in photodegrading rhodamine B.

Neste trabalho, compósitos híbridos metal/polímero (nanopartículas de ouro/polipirrol) foram sintetizados a partir da polimerização química do pirrol sobre a superfície de nanopartículas metálicas estabilizados por um agente surfactante (dodecil sulfato de sódio). A posterior solubilização do compósito em álcool polivinílico permitiu a obtenção de uma matriz orgânica auto-sustentável, flexível, com boa resistência mecânica e aplicável na detecção de compostos voláteis (com especial atenção ao metanol). Nessa direção, foram otimizadas as condições de preparação do compósito, no sentido de promover a detecção e quantificação do metanol em misturas com etanol, com o intuito de aplicar o dispositivo no reconhecimento de resquícios de metanol em bebidas alcoólicas. Dos sistemas analisados, a sensibilidade dos dispositivos se mostrou diretamente proporcional à constante dielétrica do volátil utilizado, indicando que interações físicas ocorrem na matriz na presença de voláteis.

In this study, hybrid composites of gold nanoparticles and polypyrrole (AuNPs-PPy) were manufactured by chemical polymerization of the pyrrole monomer on the surface of metal nanoparticles, which were then incorporated in a poly(vinyl alcohol) (PVA) matrix to be exploited in sensing technologies for detecting methanol. The preparation conditions were optimized to maximize sensitivity, allowing for the determination of relative concentrations of methanol molecules in binary mixtures of methanol/ethanol. This was carried out using the electrical response of the sensor, which depends on the dielectric constant of the volatile organic compounds.