Multilayer ionic conductors

The substitution of the two-sided tape with a film of an ionic conductor gives (Fig. 24) a triple-layered muscle working in air.114 The tape now acts as a solid electrolyte. Nevertheless, the system only works if the relative humidity in air surpasses 60%. Under these conditions, movements and rates similar to those shown by a triple layer working in aqueous solution were obtained. This device was developed in cooperation with Dr. M. A. De Paoli from the Campinnas University (Campinnas, Brazil). At the moment several groups are developing actuators, muscles, and electrochemomechanical devices based on bilayer or multilayer structures.115-125... 

Polarizing the metal in acid above ca. 1.80 V results in the formation of a reddish brown oxide layer which on reduction yields a relatively active form of the finely divided metal, i.e., a type of gold black. The reactions involved were investigated using potential sweep techniques by Lohrengel and Schulze, who found that rapid growth in add required a potential in excess of 2.0 V a multilayer film was clearly formed under such conditions as two, and occasionally three, peaks were recorded on the cathodic sweep. These authors postulated that while the inner layer was both a poor electronic and ionic conductor, the reverse conditions prevailed for the thicker outer film, which they also suggested was rather compact in character. 

The reason for Nafion LB-film fabrication was the wish to obtain the highly ordered systems from perfluorinated ion exchange polymer with multilayered structure, where the ionic layers (conductors) would alternate with fluorocarbon polymer layers (insulators), and to investigate the properties of such films.74 This polymer contains a hydrophobic fluorocarbon polymeric chain and hydrophilic ionic groups, so it is sufficiently amphiphilic it has a comblike structure that makes it a suitable polymer for LB-film deposition. 

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