Authors: Mohamed J M Jafeen Mohamed A Careem Steen Skaarup
Publish Date: 2009/10/17
Volume: 16, Issue: 1, Pages: 1-6
Abstract
Polypyrrole films have been characterized by simultaneous cyclic voltammetry driven forcedisplacement measurements The aim was to clarify the role of cations in the electrolyte on the speed of response and on the strain of the film The strain as a function of actuation frequency was studied in alkali metal chloride aqueous electrolytes The intention was to test the hypothesis of the division of the inserted H2O molecules into categories a smaller number strongly bound to the cation corresponding to the inner solvation shell and a larger number entering the film after the insertion of the cations because of forces related to osmotic pressure difference The two processes have very different time constants The solvated H2O molecules are associated directly with the cations and are therefore inserted in a faster process whereas the second type enters the film much more slowly At higher frequencies the strain depends almost exclusively on insertion of strongly solvated cations and therefore depends on the hydration number of the cations Li+ hydration number ~54 gives more strain than Na+ ~44 and much more than Cs+ ~0 as predicted by the model
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