Effect of the Dopant Ion

Since the size of the dopant ion can be varied considerably, it is expected that the extent and speed of actuation will be very dependent on dopant ion size. The effect of dopant ion on actuation has been most commonly investigated by altering the composition of the test 

The extent of anion vs cation movement in the PPy.pTS was also found to depend on the electrolyte used. Monovalent cations (Na , K ) were found to be incorporated into the polymer during reduction to a greater degree than divalent cations (Mg +, Ca +) [33]. Okamoto et al. [35] also reported that in the cation derived movement of PPy.pTS benders in different aqueous solutions, there were significant differences in the extent and speed of actuation that was related to the size of the cation in solution. They found that the actuator moved more slowly with larger cations and that, over a certain cation size, neither the oxidation / reduction current nor bending was observed. 

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Bipolaron transport offers a reasonable explanation for spinless transport in PA and PPP. The model is not specific to PA, in that it does not require a degenerate ground state. Our model for charge transport via bipolarons in PPP is applicable to the broad range of conducting polymer systems. It should be emphasized, however, that we have made no explicit consideration of the effect of the dopant ion array on the transport process. 

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