Quasi-equilibrium volume changes of polyaniline films upon redox switching. Formal potential distribution and configurational modeling.
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.
Lizarraga
Leonardo
L
Instituto de Química Física de los Materiales, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C. Universitaria, Pabellon II, C1428EHA Buenos Aires, Argentina.
Andrade
Estela M
EM
Florit
María I
MI
Molina
Fernando V
FV
D000814:Aniline Compounds / Q000737:chemistry*; D004563:Electrochemistry; D008567:Membranes, Artificial; D008956:Models, Chemical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry
D000814:Aniline Compounds; D008567:Membranes, Artificial; D011108:Polymers; D013464:Sulfuric Acids; C416807:polyaniline; C033158:sulfuric acid