Constructing a BNNS/aramid nanofiber composite paper via thiol-ene click chemistry for improved thermal conductivity

Benefiting from its superior insulation and outstanding environmental adaptability, aramid nanofibers (ANFs) composite paper has attracted tremendous attention in the flexible electronics and electronic packaging field. However, the extremely low thermal conductivity of aramid nanofiber paper faced a serious challenge under the rapidly increasing heat dissipation demand. Herein, boron nitride nanosheets (BNNS) were introduced to ANFs paper via a controllable vacuum-assisted filtration, and hydrogen bonding and light-induced "thiol-ene" click chemistry were proposed to improve the interfacial combination. Specifically, BNNS was prepared via the microwave-assisted hydrothermal method with subsequent sulfhydryl functionalization (f-BNNS) and s-ANFs (grafted ANFs) were prepared by deprotonation of chopped aramid fibers and then treated with KH570 coupling agent. The results showed that the through-plane thermal conductivity (TC) of f-BNNS/s-ANFs composite paper reached 0.224 W/m K with 50 wt% f-BNNS loading, exhibiting an increase of 540% and 184%, respectively, compared with pure ANFs paper and BNNS/ANFs paper. The abundant hydrogen bonding and covalent bonding via "thiol-ene" click chemistry between f-BNNS and s-ANFs contributed to enhanced interface and interlayer bonding, and the continuous interconnected thermal conductive network constructed by f-BNNS was conducive to improving TC. Meanwhile, the composite paper held excellent mechanical properties and reliable electrical insulation.