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、349.2oC和278.7oC，明顯優于普通PI膜（1.4×1013 Ω·cm、1.4 GPa、332.8oC和266.6oC）。