Synthesis, Characterization, and Electrochemistry of Nanotubular Polypyrrole and Polypyrrole-Derived Carbon Nanotubes

Polypyrrole nanotubes (PPy-NTs) were prepared by the oxidation of pyrrole with iron(III) chloride in the presence of a structure-guiding agent, methyl orange. Upon carbonization of the salt form of PPy-NTs, the conducting nitrogen-containing nanotubular carbonaceous material (C-PPy-NT) was obtained. The morphology, structure, and physicochemical properties of PPy-NTs in salt and base form as well as C-PPy-NTs were investigated by transmission electron microscopy, Fourier transform infrared and Raman spectroscopies, conductivity measurements, elemental microanalysis, inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, and nitrogen physisorption. Results of the material characterization were linked to their electrochemical behavior. Specific capacitance of around 120 F g(-1) at low potential sweep rate of 5 mV s(-1) was observed for original PPy-NTs. However, when the potential sweep rate was increased to 100 mV s(-1), PPy-NT salt retained the value of specific capacitance, while the capacitance of PPy-NT base decreased by 70%. Upon carbonization of PPy-NT salt, the specific capacitance was doubled and capacitance fade measured in the interval 5-100 mV s(-1) was determined to be around 45%. It is proposed that the absolute value of specific capacitance is determined by specific surface area and surface functional groups, while the capacitance fade is determined by the conductivity of the electrode material. In this manner, a linear relationship between the percent of capacitance fade and the logarithm of the conductivity was revealed. C-PPy-NTs were also tested as an electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. High ORR activity was observed, characterized by the onset potential of -0.1 V versus saturated calomel electrode and the apparent number of electrons consumed per oxygen molecule higher than 3. Appreciable ORR activity can be linked with a high fraction of mesopores and the presence of surface functional groups, especially pyridinic and pyrrolic nitrogens, and also with a high degree of structural disorder

A new precursor for conducting polymer-based brush interfaces with electroactivity in aqueous solution

We present the synthesis of a novel conducting polymer (CP) incorporating both pyrrole and thiophene units in its monomer, which is also substituted with an initiator for grafting of sidechains by atom-transfer radical polymerisation (ATRP). The precursor monomer for the CP macroinitiator, 2-(2,5-di(pyrrol-2-yl)thiophen-3-yl)ethyl 2-bromopropanoate) (PyThon) is very readily electropolymerised at low monomer concentrations and low applied potentials. Density functional theory (DFT) predictions of ionisation potentials and spin-charge distribution for PyThon are in good agreement with these experimental results. We present also the grafting of sidechains from electropolymerised PolyPyThon (PPyThon) to yield surface-confined polymer brushes. Functionalisation with polystyrene (PS), poly(2,3,4,5,6-pentafluorostyrene) (PFS) and poly(ethylene glycol) methyl ether acrylate (PEGMEA) is demonstrated and confirmed by FT-IR and water contact angle measurements. These PPyThon-based molecular brushes are electroactive in both water and acetonitrile, and show evidence of changes in surface conformation related to the redox state of the CP. The growth of human fibroblasts on PPyThon films is also demonstrated, indicating good biocompatibility of the polymer. We conceive PPyThon-based molecular brushes as a substrate for electrical stimuli-responsive surfaces with application particularly in the biomedical field

Grafting from Poly(3,4-ethylenedioxythiophene): A Simple Route to Versatile Electrically Addressable Surfaces

We demonstrate a simple route to versatile electrically addressable conductive polymer graft copolymer systems. The monomer of poly­(3,4-ethylenedioxythiophene), one of the commercially most important conductive polymers, was modified by the addition of an ATRP-initiating site to grow brushes from. The modified monomer is easily accessible by a one-step synthesis from the commercially available 2,3-dihydrothieno­[3,4-<i>b</i>]­[1,4]­dioxin-2-yl)­methanol. The modified monomer is subsequently electropolymerized onto large area gold-coated electrodes and utilized as a backbone for grafting pH-responsive poly­(acrylic acid) brushes from

Synthesis, Characterization, and Electrochemistry of Nanotubular Polypyrrole and Polypyrrole-Derived Carbon Nanotubes

Polypyrrole nanotubes (PPy-NTs) were prepared by the oxidation of pyrrole with iron(III) chloride in the presence of a structure-guiding agent, methyl orange. Upon carbonization of the salt form of PPy-NTs, the conducting nitrogen-containing nanotubular carbonaceous material (C-PPy-NT) was obtained. The morphology, structure, and physicochemical properties of PPy-NTs in salt and base form as well as C-PPy-NTs were investigated by transmission electron microscopy, Fourier transform infrared and Raman spectroscopies, conductivity measurements, elemental microanalysis, inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, and nitrogen physisorption. Results of the material characterization were linked to their electrochemical behavior. Specific capacitance of around 120 F g(-1) at low potential sweep rate of 5 mV s(-1) was observed for original PPy-NTs. However, when the potential sweep rate was increased to 100 mV s(-1), PPy-NT salt retained the value of specific capacitance, while the capacitance of PPy-NT base decreased by 70%. Upon carbonization of PPy-NT salt, the specific capacitance was doubled and capacitance fade measured in the interval 5-100 mV s(-1) was determined to be around 45%. It is proposed that the absolute value of specific capacitance is determined by specific surface area and surface functional groups, while the capacitance fade is determined by the conductivity of the electrode material. In this manner, a linear relationship between the percent of capacitance fade and the logarithm of the conductivity was revealed. C-PPy-NTs were also tested as an electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. High ORR activity was observed, characterized by the onset potential of -0.1 V versus saturated calomel electrode and the apparent number of electrons consumed per oxygen molecule higher than 3. Appreciable ORR activity can be linked with a high fraction of mesopores and the presence of surface functional groups, especially pyridinic and pyrrolic nitrogens, and also with a high degree of structural disorder