Electrochemically Prepared Polypyrroles from Aqueous Solutions

Abstract

ABSTRACT:Polypyrrole (PPy) films generated electrochemically from aqueous solutions have been found to have also good electrical conductivity. PPy films with the counter anions TsO-, so;, and NO; showed compact structure with apparent densities close to their flotation densities. The oxidative stability of PPy films has been compared by the value of the oxidation peak Epa around l.OV (vs. SCE) in the cyclovoltammogram. Prolonged electrolysis at +0.8V led to oxidative degradation. The temperature dependence of the conductivity followed the variable range hopping equation. However voltage shorted compaction (VSC) conductivity measurements might show pronounced differences at low temperatures for some of these films. No significant frequency dependence of the conductivity was found up to 35 GHz. In the IR spectra of electrochemically reduced PPy film by transmission the v (N-H) and sp 2 v (C-H) absorption bands were observed with no sp 3 v (C-H) bands. On grinding the reduced film with KBr to make powder compact the sp 3 v (C-H) absorption bands appeared indicating a mobile proton on theN-atom of the pyrrole ring. Definite evidence from IR spectra for the de-intercalation of the counter anion of the conducting PPy film during electrochemical reduction and chemical compensation has been obtained. 2 Recently it was found that pyrrole could be electrochemically polymerized and intercalated in aqueous solution with various types of counter anions to give PPy films of good conductivity, including detergent anions as n-alkyl sulfates, sulfonates, 3 alkyl aryl sulfonates, 4 tosylate anion, 4 and polymeric anions as polyvinyl sulfate and polystyrene sulfonate, 5 polymethacrylate, and sulfonated polyvinyl alcohol 6 as the counter anion. In our laboratory we found that with SO;', N03, and TsO-as the counter anions we can get compact conducting PPy films containing less than 20% void volume, other counter anions gave films of 70-85% void. 7 • 8 In this paper results of our recent investigation 9 on these dense conducting PPy films are summarized including morphology, oxidative stability, metallic conduction, chain structure, deintercalation and re-intercalation of the counter anions. A brief account for the molecular composites containing PPy is also given. MORPHOLOGY AND DENSITYConducting PPy films with Cl04, BF4, and PF6 as the counter anion show a morphology of hollow bowls of 20-30 11m diameter and consequently have very low apparent density 157

Templateless electrogeneration of polypyrrole nanostructures: impact of the anionic composition and pH of the monomer solution

“…Li has shown that the Py polymerization rate is directly proportional to the anion concentration of the monomer solution (for [A -] < 1 M). 23 For electrochemical PPy synthesis, various parameters such as the applied potential or the anodic current, 24 the concentration of monomer, 25 the nature of the supporting electrolyte, 26 and the nature of the working electrode 27 have an influence on the growth kinetics and the final structure of the polymer. 28,29 Polypyrrole nanostructures have been obtained using pyrrole solution containing either monohydrogenophosphate 28 or mixing of monohydrogenophosphate and dihydrogenophosphate (phosphate buffer solution (PBS)) [30][31][32][33][34][35] or carbonate.…”

Conducting polymer coatings in electrochemical technology Part 2 – Application areas

“…72 The reversible redox chemistry of these polymers indicates that these materials may be used as thin flexible and robust electrodes in rechargeable storage batteries. [73][74][75][76] An advantage of using electroactive polymers rather than metals is that the charging and discharging reactions (redox doping and undoping) create charged carriers along the conjugated backbones and there is no deposition or dissolution of the electrode material.…”

Electrochemical materials science: calculation vs. experiment as predictive tools in tailoring intrinsically conducting polythiophenes

“…In addition to these effects, which act at molecular level, bulk conductivity values are also dominated by electron transfer between grain boundaries and variations in morphology [30,31]. Thus, the bulk conductivity of a conjugated polymer may be described by Eq.…”