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We present experimental measurements and theoretical predictions of ion transport in agar gels during reversible electroporation (ECT) for conditions typical to many clinical studies found in the literature, revealing the presence of pH fronts emerging from both electrodes. These results suggest that pH fronts are immediate and substantial. Since they might give rise to tissue necrosis, an unwanted condition in clinical applications of ECT as well as in irreversible electroporation (IRE) and in electrogenetherapy (EGT), it is important to quantify their extent and evolution. Here, a tracking technique is used to follow the space-time evolution of these pH fronts. It is found that they scale in time as , characteristic of a predominantly diffusive process. Comparing ECT pH fronts with those arising in electrotherapy (EChT), another treatment applying constant electric fields whose main goal is tissue necrosis, a striking result is observed: anodic acidification is larger in ECT than in EChT, suggesting that tissue necrosis could also be greater. Ways to minimize these adverse effects in ECT are suggested.

We present experimental results and a theoretical macroscopic model on the effects of viscosity in thin-layer electrochemical growth. The viscosity was changed through glycerol additions; simultaneous use was made of optical and schlieren techniques for tracking concentration and convective fronts, while pH indicators were used for migratory fronts. The theoretical model describes diffusive, migratory, and convective ion transport in a fluid subject to an electric field. The equations are written in terms of dimensionless quantities, in particular, the Migration, Peclet, Poisson, Reynolds, and electrical Grashof numbers, which are found to depend on viscosity. Experiments reveal that with increasing viscosity, convection decreases, concentration profiles are less pronounced, while electric resistance and voltage increase. Concentration and convective fronts slow down with viscosity, but their time scaling follows the same law as for solutions without glycerol, only differing by a constant. Moreover, under constant electrical current, an increase in viscosity yields slower deposit front velocities, a more uniform deposit with smaller separation between branches, i.e., a change in morphology from more separated compact trees to a more dense, fractal-like structure. © 2001 The Electrochemical Society. All rights reserved.

The quasi-equilibrium electrochemomechanical behavior of relatively thick polyaniline films in sulfuric acid is investigated through experimental measurements and theoretical modeling. The leucoemeraldine (LE)-emeraldine (EM) conversion, or redox switching, is studied. The dependence of film volume and electrochemical charge is determined as a function of applied potential. It is observed that the film volume follows the charge, showing an expansion during the second half of the LE-EM oxidation. The model postulates the existence of a stable intermediate, protoemeraldine (PE), with a formal potential distribution for the PE-EM reaction. The volume change is modeled statistically considering contributions from mixing, polymer deformation, and electrostatic charge. The model shows very good agreement with the experiments, indicating that, in the conditions studied, the deformation contribution dominates the volume changes as a result of the conformational modifications undergone by the polymer in the PE-EM oxidation.

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Composites of cobalt ferrite nanoparticles in a polypyrrole (PPy) matrix have been synthesized in acid media and characterized by X‐ray diffraction studies, scanning and transmission electron microscopy observation, thermogravimetric analysis, conductivity, and infrared spectroscopy measurements. Two types of composites were prepared: one including dodecylbenzenesulphonic acid as a particle protector and another one without protection. The magnetic behavior was studied through DC magnetization measurements; hysteresis loops were observed, showing ferromagnetic behavior for particles and composites. Materials with particle protection showed magnetic parameters independent of the PPy/ferrite ratio; in the absence of protector, both the coercivity and remanence ratio decreased as the PPy/ferrite ratio increased. These results are attributed to conducting polymer effects on the ferrite particles, affecting the magnetic anisotropy. On the other hand, composites with low PPy/ferrite ratio showed positive magnetoresistance of up to 20% at room temperature, indicating an effect of the magnetic particles on polymer conduction. POLYM. COMPOS., 39:4617–4627, 2018. © 2017 Society of Plastics Engineers