Boosting thermal conductivity of boron nitride incorporated polymer composites via hydrogen bonding engineering.

Enhancing the thermal conductivity of polymer-based composites is critical for effective thermal management in power electronics. A common strategy involves incorporating high-thermal-conductivity fillers such as graphene and boron nitride nanosheets (BNNS). However, practical enhancements often fall short of theoretical predictions due to interfacial thermal resistance (R_Kapitza). Here, we address this challenge by engineering the hydrogen bond density (HBD) at the filler-matrix interface. By grafting 3,4-dihydroxyphenylalanine (DOPA) onto polyvinyl alcohol (PVA), we synthesized PVA-DX matrices (X = 0, 8, 12, 17, 24) with tunable HBDs. Incorporation of BNNS into these matrices revealed that higher interfacial HBD significantly reduces R_Kapitza, thereby enhancing the composite's thermal conductivity (κ_c). We achieved an exceptionally low R_Kapitza of 0.60 × 10^-8 m² K W^-1, corresponding to a filler effectiveness (κ_c/∅_f) of 120 W m^-1 K^-1. Notably, at a BNNS loading of 70 vol%, increasing the interfacial HBD to 2.14 mmol cm^-3 achieves a κ_c of 51.01 W m^-1 K^-1, which is 1.45 times higher than the 35.29 W m^-1 K^-1 attained at an HBD of 0.5 mmol cm^-3. This study underscores the critical role of interfacial hydrogen bonding in optimizing thermal transport and provides a robust framework for designing high-performance polymer composites for advanced thermal management applications.