Polymer Grafting of Boron Nitride Nanosheets via Reduction Chemistry and Their Reinforcement for Polymeric Composite

Covalent functionalization of hexagonal boron nitride nanosheets (BNNSs) is very challenging because of their surface inactivity. In this work, a simple reductive activation method is reported to covalently decorate BNNSs with polymers. BNNSs are initially negatively charged through effective reductive treatment and subsequently reacted with bromine‐terminated poly(methyl methacrylate) chains bearing different molecular weights to obtain a series of polymer‐grafted BNNSs, which greatly enhances their compatibility and dispersibility within acetone. With the increase of the molecular weight, grafting ratio and the density of grafted chains on BNNS surfaces show decreasing trends due to steric hinderance. Addition of functionalized BNNSs at a low filler content significantly improves reinforcement performance for polymer composites. The functionalization via the reduction treatment represents a novel and versatile route to anchor a range of functionalized species to manipulate surface chemistry toward the production of functional BNNSs for broad applications. Polymer‐modified boron nitride nanosheets (BNNSs) are synthesized by initial reductive treatment and subsequent reaction with bromine‐terminated poly(methyl methacrylate) chains. The functionalized BNNSs formed via BC bonding through this facile reductive activation method exhibit excellent dispersibility in acetone. The use of polymer‐modified BNNSs as a filler leads to remarkable mechanical reinforcement for polymeric composites.