A facile strategy of constructing pH-sensitive mesoporous silica nanoreservoirs and application in stimuli-responsive epoxy coatings

Abstract

To prepare stimuli-responsive inhibitor-loaded mesoporous silica nanoreservoirs (MSNs), a facile strategy is proposed to construct the pH-sensitive stoppers. The positively charged Zn(OH)2 colloids can readily adsorb and deposit on the surface of the negatively charged MSNs to stop the self-release of the stored benzotriazoles (BTA). Due to the decomposition of Zn(OH)2 stoppers in weakly acidic solution, the on-command release of BTA from the MSN-BTA@Zn(OH)2 nanoreservoirs is achieved in the pH range from 8.0 to 2.0. The high pH sensitivity of the nanoreservoirs is confirmed. The cumulative release of BTA at pH 7.0 is over 80 % within 15 min in comparison with the release below 50 % at pH 8.0. Furthermore, the addition of the pH-sensitive nanoreservoirs to epoxy coatings enhances the corrosion resistance of the coatings and the well on-command releasing in 3.5 % NaCl solution is achieved. Apart from the released BTA, the Zn2+ ions from the dissolution of Zn(OH)2 stoppers could also play an important role in suppressing the corrosion of mild steel substrate in the scratched area.