Phosphate enhanced self-healing property of phenylborate-based hydrogel at neutral environment

Self-healing hydrogels based on phenylboronate ester bonds are of huge interest in polymer science. However, most of these hydrogels only heal themselves at pH above their pKa (mostly > 8.0), which reduces their potential application in physiologic environments. Here, we showed that a small amount of phosphate produced stable hydrogels, able to support their self-healing at neutral pH. The hydrogel was formed by poly (3-acryloxymethylphenylboronic acid- co -N, N-dimethyl acrylamide) and poly (D-gluconamidoethyl methacrylate- co -N, N-dimethyl acrylamide) in phosphate buffer. Self-healing was observed at pH = 7.0. Intermolecular interactions between phenylboronic acid and phosphate were suggested by rheology, DSC determination and QTAIM calculations. The study represents a new mechanism to promote phenylboronate-based hydrogel formation and self-healing at neutral environment and, more importantly, provides considerable insight into their application in physiologic conditions including sensors and tissue engineering.