Adsorption and polymerization of aniline on a carboxylic group-modified fibrous substrate

A carboxylic group-modified poly(acrylonitrile) fiber (CPAN) was prepared and used as a substrate for aniline adsorption and polyaniline (PANI) deposition in this study. Results from batch adsorption tests showed that grafting of carboxylic group could substantially improve the adsorption capacity of CPAN for aniline monomer at optimal pH 3.0–6.0; however, in strong acidic solutions, both the raw poly(acrylonitrile) fiber (PAN) and the as-synthesized CPAN had no obvious adsorption for aniline. Results from in-situ polymerization tests showed that both PAN and CPAN could obviously accelerate the polymerization of aniline, as indicated from evolution of solution temperature and UV–vis spectra. However, as shown by SEM photographs, the deposited PANI was more uniform on CPAN as compared with PAN. Besides, the produced PANI/CPAN composite showed higher PANI content and conductivity than the PANI/PAN composite. The proposed mechanism was that the intermediate products of aniline polymerization were apt to adsorb on both the PAN and CPAN surfaces, and thus substantially accelerated the polymerization rates. Due to the relatively strong site-to-site electrostatic interaction and hydrogen bonding, higher content of PANI was deposited on the CPAN surface and the distribution was more uniform as compared with PAN.