Saline-Responsive and Hydrogen Bond Gating Effects in Self-Healing Polyaniline

Stimuli-responsive microcapsules that can release encapsulated small molecules under external environmental stimuli have been extensively employed in delivering small molecules to targeted sites. Here, salt-activated hydrogen bonding chemistry was exploited to develop responsive release systems for self-healing (guest) molecules from capsular polyaniline (PANI) particles. Payloads were physically entrapped within PANI nanoparticles constructed by interface-templated polymerization, where responsive payload release was achieved by using salt-dependent (sodium chloride) gradients. We propose a coactivation mechanism for release of guest molecules attributed to hydrogen bonding and polymer osmotic expansion. The release mechanism relies on a salt activator with cleavage of saline-responsive noncovalent interactions within the mesoporous particles. The responsiveness and guest release are coactivated by changes in polymer shell permeability, expansion, and polymer shell hydrophobicity. Anion hydration and its concentration (degree of doping) play a pivotal role for the ion responsiveness. NaCl stimuli offer a versatile and simple method for triggering sustained release of self-healing materials which hold enormous potential for applications in enhanced anticorrosion protection in harsh salt-attacking environments.