Surface Modification and Functionalization of Boron Nitride Nanotubes via Condensation with Saturated and Unsaturated Alcohols for High Performance Polymer Composites

Over the past decade, boron nitride nanotubes (BNNTs) have been researched extensively due to their desirable physical, thermal, and mechanical properties. However, a major challenge for BNNT utilization in applications is their poor processability and difficulty associated with their incorporation into materials and composites. The desire to incorporate BNNTs into relevant materials, specifically within the aerospace industry, calls for improving their processability. The successful grafting of reactive functionalities allows for improvements to the compatibility of BNNTs in polymer systems, allowing for the manufacturing of high performance BNNT–polymer composites. The research presented here addresses this concern, introducing a facile method for covalent surface functionalization of BNNTs with a diverse set of functional moieties allowing for homogeneous dispersibility in solvent. The grafted functionalities in this work are based on alkyl-, vinyl-, and propargyl-terminated alcohols covalently bound to BNNTs that were subjected to an oxidizing perchloric acid treatment. NMR spectroscopy, though not typically used for BNNT characterization, was successfully employed as a primary means to determine functionalization. Additional characterization methods including FTIR, SEM, TEM, and TGA also provide evidence of functionalization. Surface-functionalized materials were produced exhibiting up to 6 wt % functionality. Furthermore, visual analysis showed improved and stable dispersions lasting over 24 h, leading to potential benefits in processing for applications.