Microgravimetric study on the formation and redox behavior of poly(2-acrylamido-2-methyl-1-propanesulfonate)-doped thin polyaniline layers

A comparative study on the potentiostatic polymerization of polyaniline (PANI) in inorganic (sulfuric and perchloric) acid and mixed poly(2-acryalamido-2-methyl-1-propane-sulfonic) (PAMPSA)/inorganic acid solutions is carried out through combined electrochemical and microgravimetric techniques. It is established that polymerization in the presence of small amounts of PAMPSA in the mixed solutions results in immobilization of the polyanions in the PANI layers. The redox behavior of the PAMPSA-doped PANI layers, studied in acidic, neutral and slightly alkaline solutions shows that the electroactivity is preserved up to pH 9. PAMPSA seems to operate as a buffer, providing the necessary protons for the PANI layer in the range pH 7 to pH 9. Detailed microgravimetric measurements in buffer solutions with various cationic (Na⁺ and Cs⁺) and anionic (Cl⁻ and ClO₄⁻) species are used to elucidate the ionic transport occurring in the course of the PANI redox transition in neutral solutions. It is found that cations (different than protons) are involved in the early stage of oxidation whereas the participation of anionic species seems to be limited. Small mass fluxes and minor changes in the viscoelastic properties are observed during the redox transition in neutral and slightly alkaline solutions.     

Comparative study on the electrochemical synthesis of polyaniline in the presence of mono- and poly(2-acrylamido-2-methyl-1-propanesulfonic) acid

The electrochemical synthesis of polyaniline (PANI) layers was studied in mixed inorganic/organic acid solutions containing poly(2-acrylamido-2-methyl-1-propane-sulfonic) acid (PAMPSA) or the corresponding monomeric acid, AMPSA, under both potentiostatic and potentiodynamic conditions. Electrosynthesis in the presence of a small amount of PAMPSA in the mixed solutions resulted in accelerated polymerization in both growth modes whereas the AMPS anions slowed down the process. Scanning electron microscopic studies indicated a marked influence of the PAMPS and AMPS anions on the surface morphology of potentiostatically synthesized PANI. The electrochemical stability of PANI layers was studied by continuous potentiodynamic cycling. The PANI layers degradation behaviour was found to follow two different patterns depending on the mode of synthesis and not on the anions present in the polymerization solution.     

Alternatives toward proton conductive anhydrous membranes for fuel cells: Heterocyclic protogenic solvents comprising polymer electrolytes

Fuel cells are gaining increasing attention as a clean and promising technology for energy conversion. One of the key benefits of fuel cells compared to other methods is the direct energy conversion that enables the achievement of high efficiency. The electrolyte membrane is the most essential parts of a fuel cell unit, and consequently has been the subject of considerable research and development. Among the various types of proton conducting electrolytes examined for fuel cell applications, polymer electrolyte membranes (PEMs) are regarded as viable candidates since they enable operation of the cells at desirably low temperatures. This review describes recent progress in the design and development of high performance proton conducting PEMs, including the analysis of the design requirements and strategies for development of advanced PEMs for operation in anhydrous conditions. Some of the most widely used types of azole heterocycles are introduced and compared, particularly in terms of their performance characteristics in polyacids containing different functional groups. In addition, the latest research studies and progress in the field of azole-containing and azole-functionalized electrolyte systems are discussed and reviewed.