Hydrogen‐Bond‐Mediated Surface Functionalization of Boron Nitride Micro‐Lamellae toward High Thermal Conductive Papers

Abstract

Wide‐bandgap, layered hexagonal boron nitride (h‐BN) possesses excellent electrical insulation and ultrahigh thermal conductivity simultaneously, offering a perfect candidate for the growing demands of heating dissipations in modern chip industries and power electronics. Hybrids of h‐BN with polymers fulfill the thermal management materials (TMMs) requirement of flexibility, while the composite poses severe challenges in the interfacial bonding and excess thermal resistance. To date, the practical bonding between h‐BN intrinsic surfaces and polymer matrices remains elusive. This work reports on the effective alignment of h‐BN micro‐lamellae by introducing nitrogen‐atoms‐containing polymers as inter‐lamellae bridging mediums. Based on theoretical calculations the hydrogen bonding between polymer chains and the BN surface is revealed by differential charge densities mapping. It is shown experimentally that the neuron‐like polymer bundles strongly bonding surfaces of two neighboring h‐BN platelets as direct, microscopic evidence of the structure models. An extra alignment of h‐BN induced by this strong interfacial interaction leads to a higher degree of h‐BN stacking order, boosting the thermal conduction by eight times. These results reveal one unprecedented method to non‐covalently functionalize the h‐BN surface and expand the TMMs family in the dimension of the filler size, paving the way for exploring the larger‐sized ceramic TMMs.

Thermal Conductivity Enhancement of Polymeric Composites Using Hexagonal Boron Nitride: Design Strategies and Challenges

“…Different from covalent functionalization, non-covalent functionalization oftentimes occurs on the entire surface of h-BN instead of just the edges [ 141 ]. A common approach involves leveraging the spontaneous polymerization process of organic molecules to coat the h-BN surface with other organic molecules that exhibit excellent affinity, enhancing their affinity with the polymer matrix.…”

“…They chose polyhexamethylene guanidine (PHMG) as a bridging agent to bridge h-BN and PVA through hydrogen bonding. As a result, the TC of the composites fabricated with functionalized h-BN as a filler was increased by eight times compared with the composites constructed with non-functionalized h-BN [ 141 ]. Wang et al designed non-covalently functionalized h-BN with cationic polymer polyacrylamide (CPAM) by taking advantage of the negative charge caused by the electronegativity differences between B and N when h-BN is dissolved into water [ 77 ].…”

“…This implies that these functional groups readily bond with B, facilitating the functionalization of h-BN ( Figure 12 b) [ 125 ]. Yu et al employed the DFT method to calculate the variation in the adsorption energy of methylguanidine on h-BN for different orientations and determined that methylguanidine can establish robust adsorption through N-H...N structure with h-BN through differential charge density ( Figure 12 c) [ 141 ]. Unlike DFT, molecular dynamics methods are more effective in simulating the interaction between functionalized fillers and the polymer matrix.…”

“…( c ) Differential charge–density diagram of guanidine adsorbed by h-BN. The yellow and blue regions indicate where the charge density increases and decreases, respectively [ 141 ]. This is an open access article distributed under the terms of the Creative Commons CC BY license.…”

Probing the Optoelectronic Properties and Energy Conversion of Boron Nitride Quantum Dots: Impact of Oxygen Doping and Chemical Functionalization

“…This innovative surface functionalization aims to improve thermal conductivity in papers, potentially benefiting thermally conductive materials. [ 27 ] Torres‐Castillo et al explored a novel approach to functionalize boron nitride nanotubes (BNNTs) through photoinitiated chemical vapor deposition. [ 28 ] L’Hermitte et al experimentally studied how various surface functionalization techniques affect BN's ability to adsorb moisture and other sorption properties.…”