Polypyrrole oxidative doping

Not only do oxidatively doped polypyrrole films show significant environmental stability, but a number of these films can also be electrochemically prepared and switched in both organic and aqueous solvents [90]. While poly(N-methylpyrrole) was the only polymer of the series that exhibited a comparable electrochromic contrast in both solvents, N-benzyl (19a), N-tolyl (19b), and the parent polypyrrole showed a decrease in electrochromic contrast when comparing results obtained using organic and aqueous electrolytes. Polymers prepared using N-phenyl and N-benzoylpyrrole (20) showed no electrochromic switching in aqueous solutions. 

Song X, Gong H, Yin S et al (2014) Ultra-small iron oxide doped polypyrrole nanoparticles for in vivo multimodal imaging guided Photothermal therapy. Adv Fund Mater 24 1194—1201... 

Finally, the oxidation of D-glucose at Pt-based electrocatalysts incorporated in polypyrrole [55,56] or in polyaniline [57] was also considered. The first work [55] was carried out in Pt-doped polypyrrole films in a neutral medium (phosphate buffer) in view of biosensor applications. Then the use of Pt-Pd catalysts dispersed in PPy led to higher current densities of glucose oxidation than on pure metal dispersed in PPy. This may be related to the decrease of catalytic poisoning (by adsorbed CO as shown by infrared reflectance spectroscopy [58]), due to the presence of Pd. 

The first studies by UV-visible transmission spectroscopy were carried out using an optically transparent electrode (OTE) such as indium oxide [140,141]. Unfortunately an OTE does not allow the nature and the structure of the electrode material to be changed and these play a key role in electrocatalytic processes. Only reflectance spectroscopy is able to investigate in situ, various electrode materials [142], This was effectively checked for the first time with cobalt porphyrin-doped polypyrrole films using the electroreflectance technique [106,143]. This allowed the characterization of the redox properties of the modified PPy electrode and the determination of the redox potential of the Co"VCo" couple. The catalytic effect towards the ORR was also... 

CPVC, chlorinated poly(vinyl chloride) PVB, poly(vinyl butyral) PVdF, poly(vinyl difluoride) PMMA, poly(methyl methacrylate) PEO, poly(ethylene oxide) PPyCl, chloride-doped polypyrrole PPyTS, tosylate-doped polypyrrole PPO, poly(phenylene oxide) PP-N2, nitrogen plasma-treated polypropylene PP-NH3, ammonia plasma-treated polypropylene MC, microcalorimetry APS, aminopropyltriethoxysilane. 

High quality thin films of doped polypyrrole and doped polyaniline can be conveniently deposited during a few minutes at room temperature on glass and plastic substrates from dilute aqueous solutions of the respective monomer as it undergoes oxidative polymerization (5-5,75). We find that the deposition rate and the properties of the films are greatly dependent on the nature of the substrate surface, e.g., whether deposited on hydrophilic or hydrophobic surfaces. 

The need for high electronic conductivity has meant that work has focused on the use of the so called conducting polymers, exemplified by polypyrrole, polyaniline and polythiophene (Structures 1 to 3). These materials must be in their p-doped (partially oxidized) states (right hand side of eq. 1, for example) to exhibit sufficient electronic conductivity. Unfortunately, the p-doped polymers are cationic and will therefore tend to exclude the protons needed for the fuel cell reactions. To circumvent this problem, composites of conducting polymers with cation exchange polymers have been used. Thus p-doped polypyrrole / poly(styrene-4-sulphonate) (PSS), for example, exhibits both proton and electron conductivity (8). 

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