Graphene oxide as a self-carbocatalyst to facilitate the ring-opening polymerization of glycidol for efficient polyglycerol grafting

Grafting carbon-based nanomaterials (CNMs) with polyglycerol (PG) improves their application potentials in biomedicine and electronics. Although "grafting from" method offers advantages over "grafting to" one in terms of operability and versatility, little is known about the reaction process of glycidol with the surface groups onto CNMs. By using graphene oxide (GO) as a multi-functional model material, we examined the reactivity of the surface groups on GO toward glycidol molecules via a set of model reactions. We reveal that carboxyl groups spontaneously react with the epoxide ring with no need of catalyst, while GO catalyzes the reactions of hydroxyl groups with the epoxide of glycidol. In addition, the hydroxyl group of glycidol can open the epoxide in the basal pane of GO. The subsequent polymerization of PG is supposed to propagate at the primary and/or the secondary hydroxyl groups, generating a ramified PG macromolecule with random branch-on-branch topology. In addition, ketones, benzyl esters and aromatic ethers are found not to react with glycidol even in the presence of GO, while the aldehydes are easily oxidized into carboxyl groups under ambient condition, behaving then as the carboxyl groups. Our findings pose the foundation for understanding the polymerization mechanism of PG on CNMs.