Hydroxyl and Amino Bifunctionalized Boron Nitride Nanosheets for High-Strength and Thermoconductive Composite Films

Boron nitride nanosheets (BNNSs) have attracted more and more attention in the field of thermal management due to their excellent thermal and electrical properties. However, the low dispersity and low production yield are still a great baffle for its application. Herein, high-performance hydroxyl and amino bifunctionalized BNNSs (HA-BNNSs) were successfully prepared by the citric acid-assisted ball milling one-step method. Based on the additional friction provided by citric acid during ball milling, the aspect ratio of HA-BNNSs was up to 499 and the production yield was as high as 89.7%. Simultaneously, arising from the high functionalization rate, the HA-BNNSs show excellent dispersity in a variety of polar solvents, particularly in 50% aqueous ethanol solution. The dispersibility of HA-BNNSs was much improved to 39.8 mg/mL. Based on the good dispersibility of HA-BNNSs and strong interface interactions between HA-BNNSs and the matrix, HA-BNNSs have been introduced to aramid nanofibers (ANFs) to fabricate layered HA-BNNSs/ANF composite films for thermal management applications. In comparison with the pure BNNSs/ANF, the HA-BNNSS/ANF composite exhibits improved mechanical strength (85.6–175.6 MPa) and better thermal conductivity (8–39.5 W/m·K) at a relatively low filler content (≤50%). In summary, benefiting from the bifunctional group, improved dispersibility, and high aspect ratio, the HA-BNNSs have great application potential in the fields of composite reinforcement, drug delivery, and photocatalysis.