Polypyrrole swelling

The flow of an anodic current oxidizes the conducting polymer and the film swells. At the polypyrrole/tape interface, electrochemically stimulated conformational changes in the polymer promote an expansion that... 

Tanaka, A., W. Takashima, and K. Kaneto. 2004. Enhanced swelling behaviors of polypyrrole film doped with sulfonated polyaniline. Chem Lett 33 1470. 

The intercalation of dopants to conducting polymer chains leads to an increase in volume of up to 30 % [8], This property is used in actuators (polymer-based artificial muscles). Bilayer structure of polypyrrole-based anode and cathode is a simple model. At anode, p-doping of polymer occurs to swell, while the other side shrinks because of the expulsion of counterions. This volume changes promote a bend of the layers. The change of poles cancels the volume changes and gives rise to the movement in the opposite direction. 

The same electrochemical ion-exchange process makes the polymer change its volume so that polymer films shrink-swell following oxidation-reduction. This suggested their use as actuators and in fact poly(3-octylthiophene) [430] and polypyrrole [431-33] elec-trodeposited onto a gold-coated polyethylene strip makes it bend upon redox switching. 

Charting the conducting polymer synthesis conditions. A film of polypyrrole on the surface of the rubber is obtained by swelling the vulcanized rubber with pyrrole followed by immersion in a concentrated aqueous solution of FeCl3. The surface conductivity obtained was 10 Scm" . 

Xue and Tm [21] modified SPEEK membranes with chemically in situ polymerized polypyrrole (PPy). It was found that the solution uptake and the swelling ratio of the SPEEK/PPy decreased upon incorporation of PPy. At temperatures >60°C, the membrane in 10 vol% methanol began to lose its mechanical stabihty. XRD analysis showed that the structure was almost amorphous. The DSC and TGA measurements showed that the microstructure change of SPEEK/PPy membranes cannot be removed, even after drying the membranes. The incorporation of PPy into the SPEEK matrix decreased methanol permeation and proton conductivity. It was suggested that this is likely due to PPy particles blocking the methanol and protons. 

Figure 6. Bimorph consisting of polypyrrole ( ) and 3-hexylPT ( ). (a) in the dry state, (b) after swelling in chloroform.

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