Saline-enabled self-healing of polyelectrolyte multilayer films

Abstract

Self-healing materials have the ability of repairing or recovering themselves after suffering damages. However, few synthetic self-healing materials can keep their self-healing abilities under physiological conditions. In this work, polyurethane (PU)/carboxymethyl cellulose (CMC) multilayer films were assembled on glass slides with/without poly(diallyldimethylammonium chloride) (PDDA) precoated through the layer-by-layer technique. It was found that (CMC/PU)_n films assembled on glass slides with precoated PDDA can autonomically repair cuts of several tens of micrometers wide when contacted with normal saline. The mechanism of healing was studied using optical microscopy and SEM. Furthermore, a simple method was proposed, by combining dispersion experiments and a Student's t-test, to confirm that the damaged films healed completely. The results suggested that the healing ability of certain films could be largely enhanced by introducing a third polyelectrolyte with relative high stiffness as the innermost layer. The results provided a new design route to fabricate new coating materials with self-healing ability.