Thermal Conductivity Improvement of Polymer Films by Catechin-Modified Boron Nitride Nanotubes

Boron nitride nanotubes (BNNTs)/polyvinyl formal (PVF) composite films containing high BNNT fractions (up to 10 wt %) are fabricated. After nanotube surface modification with epicatechin gallate molecules—“catechin” (the major component of a Japanese “green” tea)—the efficient improvement of PVF thermal conductivity is achieved (∼160% at only 1 wt % BNNT loading fraction). Catechin molecules, having numerous aromatic rings, effectively interact with the nanotube surfaces via π−π bonding in such a way that catechin species mediate between BNNTs and a polymer improving the heat transfer between the matrix and fillers. Finally, the polyvinyl alcohol (PVA) polymeric composites with drastically improved thermal conductivity (∼270%, even at a BNNT fraction as low as 3 wt %) are fabricated using the analogous catechin-modification route.