Conductive polymers are versatile materials that can be applied in many different technology fields, especially green energy. They have several advantages, such as easy synthesis, low density, and cost. However, its electric conduction property is also related to material aging with great loss of their characteristics, limiting their applicability. The in-depth study of electrochemical aging can provide useful information for new strategies to overcome this problem. Thus, this work describes the use of factorial design to evaluate the influence of some synthesis variables on the aging of poly(3-hexylthiophene): electrolyte and monomer concentration and water in the synthesis of non-aqueous solution. For this, the properties of the films were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The accelerated electrochemical aging was performed by applying a potential higher than the superoxidation potential for 20 min steps. It was possible to identify two extreme cases, the conventionally synthesized polymer aged more, while the polymer obtained with the three altered parameters suffered fewer aging effects. It was possible to identify a range of different aging pathways among these. The mechanical stress caused by the several oxidation/reduction cycles of the material aligned to the increasing loss of polymer properties, potentiates aging.

Ionomeric Polymer-Metal Composites (IPMCs) are sandwich-like materials based in a polymeric membrane covered on both sides by metallic electrodes. Its operation mechanism consists of hydrated ions migration in response to an external electrical field generated between the electrodes, leading to a spatially nonuniform mass accumulation which causes the device to bend. Its performance as an actuator depends mainly on the environment's relative humidity and electrical stimuli. Consequently, IPMCs present variations in the electromechanical properties exhibiting nonlinearities and time-varying behaviors, limiting the major applications. For this reason, this paper investigated a PI controller performance to overcome these drawbacks and effectively control a Nafion-based IPMC-Li+ exposed to different relative humidities and electrical stimulis. The PI control system uses a camera with a machine vision application as a feedback sensor. Support instrumentation was developed to control the relative humidity, apply an electrical stimulus, and measure the electromechanical response. The pattern recognition algorithm implemented in the controller is efficient, with accuracy above 95%, making the feedback sensor reliable. Therefore, the PI controller was effective, stable, and capable of controlling and characterizing IPMC devices when relative humidity was above 60% at a low-frequency displacement and avoided the undesired back-relaxation phenomenon.

Abstract Ionomeric Polymer-Metal Composites (IPMC) are smart materials whose electromechanical behavior depends on the electrical stimulus intensity, membrane hydration level, and ionic migration. This paper investigates the effects of the voltage, relative humidity, and counterion type (Li+ and K+) on a Nafion-based IPMC performance. Instrumentation capable of applying an electrical stimulus and measuring the electromechanical response was developed. The ionic conductivity was obtained using Electrochemical Impedance Spectroscopy. Complementary SEM analyses were performed before and after actuation cycles. The IPMC performance improved when the electrical stimulus was 5.00 V, RH = 90%, and Li+ was used. The IPMC-Li sample is an excellent candidate to be used as an actuator since it exhibited fast actuation movement, considerable displacement, and no evident back-relaxation. However, its mechanical performance decreased over time because of a progressive increase in platinum electrode crack density and dehydration. The video analysis technique is an efficient, effective, and low-cost technique.