Concurrent alkylation and crosslinking of polyaniline for enhanced anticorrosive performance of waterborne alkyd coating

The uniform dispersion and long-term stability of hydrophobic polyaniline (PANI) in waterborne polymer matrix always remains a challenge. Here, PANI was chemically modified by 1,12-dibromododecane to prepare functionalized PANI (PANI-12Br(II)), and simultaneously achieve N-alkylation and chemical crosslinking of PANI chains. In addition, 1-bromododecane was utilized to modify PANI to prepare PANI-12Br(I) as a control. The degree of alkylation of PANI-12Br(II) was higher than that of PANI-12Br(I), as well as the content of N+ species in PANI-12Br(II). Also, the interaction between the PANI-12Br(II) chains decreased. The colloidal particle size decreased from 703.9 nm to 297.3 nm, and the dispersibility and long-term colloidal stability of PANI-12Br(II) in aqueous system were significantly improved. The water adsorption of as-prepared PANI-12Br(II)/WAR nanocomposite decreased from 18.37% to 4.27%, and the contact angle increased from 63.4° to 112.5°. Compared with WAR and PANI/WAR-0.5%, the coating resistance of PANI-12Br(II)/WAR-0.5% increased by 5 and 4 orders of magnitude, and the corrosion current density decreased by 3 and 2 orders of magnitude. The PANI-12Br(II)/WAR-0.5% displayed better long-term anticorrosive performance than PANI-12Br(I)/WAR-0.5%. The anticorrosive mechanisms were also put forward. The PANI-12Br(II) can be applied as a promising class of corrosion inhibitors in waterborne polymer matrices.