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Kunpeng Ruan and Junwei Gu*. Ordered Alignment of Liquid Crystalline Graphene Fluoride for Significantly Enhancing Thermal Conductivities of Liquid Crystalline Polyimide Composite Films. Macromolecules, 2022, 10.1021/acs.macromol.2c00491. 2020IF=5.985.（1區化學Top期刊）

https://doi.org/10.1021/acs.macromol.2c00491

Abstract

Low thermal conductivity coefficient (λ) of polyimide (PI) films are limiting their application in high-power electronic equipments, and the disordered alignment of fillers discourage efficient improvement of λ for PI-based composite films. Herein, polyethylene glycol trimethylnonyl ether is used to perform liquid crystalline modification on graphene fluoride (LC-GeF) to achieve ordered alignment. Intrinsically thermally conductive liquid crystalline PI (LC-PI) matrix is utilized to fabricate thermally conductive LC-GeF/LC-PI composite films. In-plane λ (λ_∥) and through-plane λ (λ_⊥) of 15 wt% LC-GeF/LC-PI composite films reach 4.21 and 0.63 W/(m·K), 446.8% and 320.0% higher than λ_∥ (0.77 W/(m·K)) and λ_⊥ (0.15 W/(m·K)) of normal PI films, 99.5% and 96.9% higher than λ_∥ (2.11 W/(m·K)) and λ_⊥ (0.32 W/(m·K)) of LC-PI films, also higher than 15 wt% GeF/LC-PI composite films. Additionally, LC-GeF/LC-PI composite films possess more excellent insulating, mechanical and thermal properties than GeF/LC-PI composite films.

聚酰亞胺（PI）膜較低的本征導熱系數（λ）限制了其在高功率電子設備中的應用。常規PI基導熱復合膜中的導熱填料往往無序排列，阻礙了λ的高效提升。本文采用聚乙二醇三甲基壬基醚（TMN）對“溶劑插層-超聲剝離”法制備的氟化石墨烯（GeF）進行液晶化改性（LC-GeF），再與本征導熱液晶PI（LC-PI）基體復合制備LC-GeF/LC-PI導熱復合膜。當LC-GeF導熱填料的質量分數為15 wt%時，LC-GeF/LC-PI導熱復合膜室溫下的面內λ（λ_∥）和面間λ（λ_⊥）分別達到4.21 W/(m·K)和0.63 W/(m·K)，較普通PI膜的λ_∥（0.77 W/(m·K)）和λ_⊥（0.15 W/(m·K)）提升了446.8%和320.0%，較本征導熱LC-PI膜的λ_∥（2.11 W/(m·K)）和λ_⊥（0.32 W/(m·K)）提升了99.5%和96.9%，也高于相同填料用量下GeF/LC-PI導熱復合膜。此外，相同填料用量下，LC-GeF/LC-PI復合膜還具有較GeF/LC-PI復合膜更加優異的絕緣性能、力學性能和熱性能。

本文亮點

1. 利用非離子型表面活性劑TMN對GeF進行液晶化改性，基于TMN和GeF間氫鍵作用實現了LC-GeF導熱填料的微觀有序排列。

2. 當LC-GeF導熱填料的質量分數為15 wt%時，LC-GeF/LC-PI導熱復合膜室溫下的λ_∥和λ_⊥分別達到4.21 W/(m·K)和0.63 W/(m·K)，較普通PI膜的λ_∥（0.77 W/(m·K)）和λ_⊥（0.15 W/(m·K)）提升了446.8%和320.0%。

3. LC-GeF/LC-PI導熱復合膜具有優異的絕緣性能、力學性能和熱性能，15 wt% LC-GeF/LC-PI導熱復合膜的體積電阻率、楊氏模量、玻璃化轉變溫度和耐熱指數分別為7.9×10¹⁴ Ω·cm、2.4 GPa、349.2^oC和278.7^oC，明顯優于普通PI膜（1.4×10¹³ Ω·cm、1.4 GPa、332.8^oC和266.6^oC）。