Pyrrole

A CA or CA:IBU membrane was immersed in an aqueous solution of 0.05 mol/L pyrrole (98%, Sigma-Aldrich, Stainheim, Germany) for 10 min to allow pyrrole impregnation. After this period, an oxidising solution of iron (III) chloride hexahydrate (FeCl₃·6H₂O, purity 99%, Chem-Lab NV, Zedelgem, Belgium)—in a mass ratio of 2:1 (FeCl₃:pyrrole) [12 (link)]—was gently added. The pyrrole polymerisation was carried out for 90 min, and after that time, the membranes were carefully removed from the solution and washed with ultrapure water (Elix^® purification system, Merck Millipore) and ethanol (Honeywell Riedel-de Haën, Seelze, Germany, 99.5%) to extract the by-products and unreacted residues. Finally, membranes were dried at room temperature. This functionalisation process is illustrated in Figure 1b.

Pyrrole (Sigma-Aldrich) was purified by passing it through aluminum oxide (Sigma-Aldrich) column before use. The polymerizing solution for PPy/pTS was prepared with 0.15 M Pyrrole and 0.1 M para-toluene sulfonate (pTS) (Sigma-Aldrich) in deionized (DI) water. For the preparation of PPy/PSS and PPy/Cl, the solutions of 0.1 M sodium polystyrene sulfonate (NaPSS) (Sigma-Aldrich) and 0.1 M sodium chloride (NaCl) (Sigma-Aldrich) were prepared with 0.15 M Pyrrole, respectively. A PPy film was electrodeposited galvanostatically on indium-tin oxide (ITO) coated glass electrodes or gold electrodes using the three-electrode system consisting of a VersaSTAT3 electrochemical working station (Princeton Applied Research, AMEMEK Scientific Instrument, Berwyn, USA). A platinum wire electrode was used as a counter electrode, and a saturated calomel electrode (SCE, CH Instrument, Inc., TX, USA) was used as a reference electrode. The current density of 1 mA/cm² was applied to the electrolyte solution. Charges of 50 mC/cm² or 100 mC/cm² were employed for the electrochemical PPy deposition. The polymerized PPy films were then carefully washed with DI water.

Reagents used in the polypyrrole nanosuspension synthesis consisted of pyrrole (≥99%, Aldrich, San Louis, MO, US), hydrochloric acid (37% purchased from Sigma Aldrich, San Louis, MO, US), ammonium persulfate (≥98%, Fluka, Bucharest, Romania), poly (sodium 4-styrenesulfonate) solution (Mw 70,000, 30% wt) and (Mw 200,000, 30% wt) purchased from Sigma Aldrich (San Louis, MO, US).
For the synthesis of PPy:PSS, pyrrole monomer (0.053 mmol) was introduced dropwise in 40 mL of HCl 0.03 M. The solution was stirred vigorously for 1 h and then concentration 3 × 10⁻⁴ mMol of PSS solution was added dropwise. After 1 h, 5 mL of a 6 × 10⁻³ M ammonium persulfate solution was added to the mixture as oxidizing agent to start pyrrole polymerization for 12 h at room temperature. After this time, a characteristic black coloured suspension was obtained.