Liquid Crystal-Engineered Polydimethylsiloxane: Enhancing Intrinsic Thermal Conductivity through High Grafting Density of Mesogens

HT Zhang and YQ Guo and YZ Zhao and QY Zhu and MK He and H Guo and XT Shi and KP Ruan and J Kong and JW Gu, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 64, e202500173 (2025).

DOI: 10.1002/anie.202500173

The increasing power and integration of electronic devices have intensified serious heat accumulation, driving the demand for higher intrinsic thermal conductivity in thermal interface materials, such as polydimethylsiloxane (PDMS). Grafting mesogens onto PDMS can enhance its intrinsic thermal conductivity. However, the high stability of the PDMS chain limits the grafting density of mesogens, restricting the improvement in thermal conductivity. This work proposes a new strategy to efficiently introduce mesogens onto PDMS through ring-opening copolymerization of liquid crystal cyclosiloxane and octamethylcyclotetrasiloxane, enhancing the grafting density. The relationship between the grafting density and intrinsic thermal conductivity of liquid crystal polydimethylsiloxane (LC-PDMS) is investigated by nonequilibrium molecular dynamics (NEMD) simulations. Based on the simulation results, LC-PDMS with enhanced intrinsic thermal conductivity is synthesized. When the grafting density of mesogens reaches 77.4 %, its intrinsic thermal conductivity coefficient (lambda) increases to 0.56 W/(m & sdot;K), showing a 180.0 % improvement over ordinary PDMS (0.20 W/(m & sdot;K)). The LC-PDMS also exhibits the low dielectric constant (& varepsilon;, 2.69), low dielectric loss tangent (tan delta, 0.0027), high insulation performance (volume resistivity, 3.51x1013 Omega & sdot;cm), excellent thermal stability (heat resistance index, 217.8 degrees C) and excellent hydrophobicity (water contact angle, 137.4 degrees), fulfilling the comprehensive requirements of advanced thermal interface materials.

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