Protonation-driven assembly of exfoliated boron nitride in bacterial cellulose for a green strategy on flexible, high-conductivity thermal films

Abstract

Cellulose-based thermally conductive composites are gaining attention as sustainable thermal management materials, but achieving high thermal performance while preserving mechanical integrity remains challenging. Herein, we present a facile, eco-friendly approach for fabricating high-performance bacterial cellulose (BC)/hexagonal boron nitride (h-BN) composite films. We employed 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (oBC) as a green dispersing medium for h-BN exfoliation in water and a highly crystalline matrix. A key innovation is the introduction of a protonation process, which induces interfibrillar cross-linking in the oBC matrix and enhances the dispersion stability of large-sized h-BN platelets (30 μm). This protonation strategy facilitated the preferential in-plane orientation of h-BN platelets within the oBC network. The synergistic effect of h-BN size, loading concentration, and protonation-induced orientation yielded films with exceptional in-plane thermal conductivity (35.15 W m⁻¹ K⁻¹). The protonated films demonstrate superior thermal performance and higher tensile strength (11.22 MPa). The thermal management capability of these films was demonstrated in light-emitting diode (LED) cooling applications, where they exhibited superior heat dissipation. This work provides a sustainable pathway for developing high-performance thermal interface materials through rational design of biopolymer-ceramic interfaces and strategic control of filler orientation, offering promising solutions for thermal management in next-generation flexible electronics and energy devices.