Preparation of Boron Nitride Nanosheets via Deep Eutectic Solvent‐Assisted Exfoliation and Investigation on Thermal Conductivity of Their UV ‐Curable Composites

ABSTRACT The practical application of boron nitride nanosheets (BNNS) is hindered by the limitations of traditional organic solvents in hexagonal boron nitride (h‐BN) exfoliation, which exhibit high volatility, low efficiency, and toxicity. The intrinsic hydrophobicity and chemical inertness of h‐BN further complicate exfoliation. To address these challenges, this study developed deep eutectic solvents (DES) as green and efficient alternatives. Four DES systems were synthesized with a 1:3 molar ratio, combining tetrabutylammonium chloride (TBAC) as a hydrogen bond acceptor (HBA) with four butanediol isomers (1,2‐butanediol, 1,3‐butanediol, 1,4‐butanediol, and 2,3‐butanediol) as hydrogen bond donors (HBD). h‐BN was exfoliated via ultrasonic treatment, and characterizations were used to explore the correlation between DES properties and exfoliation efficiency. Results showed DES with weaker hydrogen bond basicity and higher hydrogen bond strength enhanced h‐BN exfoliation efficiency. The TBAC/1,4‐butanediol system achieved the highest exfoliation efficiency (33.6%), yielding BNNS with a thickness of 3–5 nm and lateral dimensions of 1–2 μm. The BNNS were incorporated into a photosensitive silicone resin matrix polydimethylsiloxane (PDMS) to fabricate PDMS/BNNS composites through UV curing. At 20 wt% BNNS loading, the composite exhibited an in‐plane thermal conductivity of 6.221 W/(m K), and reduced the surface temperature of an LED lamp by 5.9°C, indicating its potential as a thermal interface material for heat dissipation in electronic devices.