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區化學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.
電子產品的高功率化和高集成化使其中電子元器件的熱量積聚問題愈發嚴峻，進而對聚二甲基硅氧烷（PDMS）等熱界面材料的本征導熱性能提出了更高的要求。在大分子鏈上接枝液晶基元有利于PDMS本征導熱性能的提升，但是PDMS主鏈穩定性過高，不易發生反應，導致液晶基元的接枝密度過低，本征導熱性能提升有限。本文提出通過液晶環硅氧烷與八甲基環四硅氧烷開環共聚進而在PDMS上高效引入液晶基元、提升液晶基元接枝密度的新策略。首先通過非穩態分子動力學模擬（NEMD）研究液晶基元接枝密度與液晶聚二甲基硅氧烷（LC-PDMS）本征導熱性能的內在聯系，進而以模擬結果為導向，基于開環共聚法成功制備了本征高導熱LC-PDMS。當LC-PDMS分子鏈上液晶基元接枝密度達到77.4%時，其本征導熱系數（λ）高達0.56 W/(m·K)，較通用PDMS（0.20 W/(m·K)）提升了180.0%。該類本征高導熱LC-PDMS還兼具低介電常數（ε，2.69）和介電損耗角正切值（tanδ，0.0027）、高絕緣性能（體積電阻率高達3.51×1013 Ω·cm）、優異熱穩定性（耐熱指數高達217.8℃）和出色疏水性（水的接觸角高達137.4o），可滿足高端熱界面材料的綜合性能需求。
論文亮點
1. 通過NEMD研究了液晶基元接枝密度與LC-PDMS本征導熱性能的內在聯系，進而以模擬結果為導向，基于開環共聚法成功制備了本征高導熱LC-PDMS。
2. 當LC-PDMS分子鏈上液晶基元接枝密度達到77.4%時，其本征λ高達0.56 W/(m·K)，較通用PDMS（0.20 W/(m·K)）提升了180.0%。
3. LC-PDMS兼具低介電常數和介電損耗角正切值、高絕緣性能、優異熱穩定性和出色疏水性，可滿足高端熱界面材料的綜合性能需求。
第一作者：張海天郵件地址：zhtnpu@163.com
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