Haitian Zhang, Yongqiang Guo, Yizhi Zhao, Qiuyu Zhu, Mukun He, Hua Guo, Xuetao Shi, Kunpeng Ruan*, Jie Kong and Junwei Gu*. Liquid Crystal-Engineered Polydimethylsiloxane: Enhancing Intrinsic Thermal Conductivity through High Grafting Density of Mesogens. Angewandte Chemie International Edition, 2025, 10.1002/anie.202500173. 2023IF=16.1. （1区化学Top期刊）

https://doi.org/10.1002/anie.202500173

Abstract

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 (λ) increases to 0.56 W/(m·K), showing a 180.0% improvement over ordinary PDMS (0.20 W/(m·K)). The LC-PDMS also exhibits the low dielectric constant (ε, 2.69), low dielectric loss tangent (tanδ, 0.0027), high insulation performance (volume resistivity, 3.51×1013 Ω·cm), excellent thermal stability (heat resistance index, 217.8oC) and excellent hydrophobicity (water contact angle, 137.4o), fulfilling the comprehensive requirements of advanced thermal interface materials.

电子产品的高功率化和高集成化使其中电子元器件的热量积聚问题愈发严峻，进而对聚二甲基硅氧烷（PDMS）等热界面材料的本征导热性能提出了更高的要求。在大分子链上接枝液晶基元有利于PDMS本征导热性能的提升，但是PDMS主链稳定性过高，不易发生反应，导致液晶基元的接枝密度过低，本征导热性能提升有限。本文提出通过液晶环硅氧烷与八甲基环四硅氧烷开环共聚进而在PDMS上高效引入液晶基元、提升液晶基元接枝密度的新策略。首先通过非稳态分子动力学模拟（NEMD）研究液晶基元接枝密度与液晶聚二甲基硅氧烷（LC-PDMS）本征导热性能的内在联系，进而以模拟结果为导向，基于开环共聚法成功制备了本征高导热LC-PDMS。当LC-PDMS分子链上液晶基元接枝密度达到77.4%时，其本征导热系数（λ）高达0.56 W/(m·K)，较通用PDMS（0.20 W/(m·K)）提升了180.0%。该类本征高导热LC-PDMS还兼具低介电常数（ε，2.69）和介电损耗角正切值（tanδ，0.0027）、高绝缘性能（体积电阻率高达3.51×1013 Ω·cm）、优异热稳定性（耐热指数高达217.8℃）和出色疏水性（水的接触角高达137.4o），可满足高端热界面材料的综合性能需求。

论文亮点

1. 通过NEMD研究了液晶基元接枝密度与LC-PDMS本征导热性能的内在联系，进而以模拟结果为导向，基于开环共聚法成功制备了本征高导热LC-PDMS。

2. 当LC-PDMS分子链上液晶基元接枝密度达到77.4%时，其本征λ高达0.56 W/(m·K)，较通用PDMS（0.20 W/(m·K)）提升了180.0%。

3. LC-PDMS兼具低介电常数和介电损耗角正切值、高绝缘性能、优异热稳定性和出色疏水性，可满足高端热界面材料的综合性能需求。

第一作者：张海天邮件地址：zhtnpu@163.com

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