Efficient covalent functionalization of multi-walled carbon nanotubes in a flow reactor

Abstract

Multi-walled carbon nanotubes (MWCNTs), widely recognized for their excellent electrical, thermal, and mechanical properties, have gained significant attention across various fields. However, aggregation due to their high Van der Waals force limits their processability and applications. Surface functionalization can offer a solution to these limitations and broadens their potential uses. Nevertheless, the low reaction rates of covalent functionalization in conventional batch reactors, caused by MWCNT aggregation, remain a significant challenge to overcome. Moreover, controlling the degree of functionalization in batch reactors is difficult. In this work, we demonstrated covalent functionalization of MWCNT with 4-bromoaniline to produce MWCNT-PhBr with high, controllable degrees of functionalization, using a customized packed-bed flow reactor. The reaction was performed under various conditions, including the reactant injection sequence, reaction time (1–3 h), temperature (60–80 ℃), and concentration of reactant (0.42–1.72 M). The resulting degree of functionalization was controlled within the range of 1.81–5.70 wt%. Notably, the highest degree of functionalization obtained under the optimized flow conditions (5.70 wt% at 70 °C and 1.72 M) represents a 2.11-fold increase compared to that achieved under the optimized batch conditions (2.70 wt% at 60 °C and 0.86 M). These results suggest that the flow system is an efficient and reliable method for synthesizing functionalized MWCNTs with the desired functional group content.