Ammonium peroxydisulfate

Aniline hydrochloride (p.a., Penta, Czech
Republic), ammonium peroxydisulfate (p.a., Lach-Ner, Czech Republic),
terephthalic acid (>98% purity, Alfa Aesar, Germany), 2-aminoterephthalic
acid (99% purity, Alfa Aesar, Germany), zirconium tetrachloride (>99.5%
purity, Sigma-Aldrich, Germany), and Nafion 117 solution (∼5%
in a mixture of lower aliphatic alcohols and water, Sigma-Aldrich)
were used as received.

p-Phenylenediamine dihydrochloride (≥98%) was purchased from Sigma-Aldrich (Buchs, Switzerland), ammonium peroxydisulfate from Lach:Ner (Neratovice, Czech Republic) and montmorillonite (Cloisite-Na⁺) from Southern Clay Products (Gonzales, TX, USA). All chemicals were used as received without any further purification.
In a typical process, 3.62 g of p-phenylenediamine dihydrochloride (PDA) was dissolved in 50 mL of deionized water. Various amounts of MMT (0 g, 2 g, 5 g, 10 g, 15 g, 25 g, 35 g and 50 g, respectively) were added into the PDA solution, and the mixture was sonicated for 5 h. The amount of 5.71 g of ammonium peroxydisulfate was dissolved in 50 mL deionized water and added to the PDA/MMT dispersion under magnetic stirring. The total concentration of monomer and oxidant in each polymerization mixture was 0.2 M and 0.25 M, respectively. After 1 h of intense stirring, the mixture was left undisturbed to polymerize for 24 h. The obtained precipitates were filtered and washed with deionized water and ethanol to remove by-products. The final products, poly(p-phenylenediamine)/montmorillonite (PPDA/MMT) composites with different amounts of MMT, were labeled as PPDA-X, where X accounts for the amount of MMT added to the reaction mixture.