Soy protein as a sustainable surfactant to functionalize boron nitride nanosheets and its application for preparing thermally conductive biobased composites

To enhance interfacial performance of thermal conductive polymer composites, low-cost and abundant plant derived soy protein isolate (SPI) was used in this study to produce surface functionalized boron nitride nanosheets (BNNS), where SPI acts as a green surfactant to disperse and exfoliate BNNS during the process. Then, biobased tannic acid-coated cellulose nanofiber (TA@CNF) motifs were synthesized to serve as a template to anchor SPI-functionalized BNNS (SPI-BNNS), wherein the TA@CNF provided versatile active surfaces to induce the formation of the interconnected network structure. The TA@CNF assembly with SPI-BNNS could easily form high thermal conductive pathways in the composite films, and the resultant films containing only 1.0 wt% of SPI-BNNS showed significantly enhanced in-plane thermal conductivity (TC) of 6.88 W m(-1) K-1, which was three times higher than that of pure TA@CNF film. Moreover, the composite films exhibited remarkable improvement in tensile strength and toughness. We attributed the simultaneously increased TC and mechanical properties to construction of the interconnected network and covalent/hydrogen bonds regulated between SPI-BNNS and TA@CNF. This research is of practical importance to value-added and high-efficiency utilization of plant resources in the future.