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区化学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.
聚酰亚胺（PI）膜较低的本征导热系数（λ）限制了其在高功率电子设备中的应用。常规PI基导热复合膜中的导热填料往往无序排列，阻碍了λ的高效提升。本文采用聚乙二醇三甲基壬基醚（TMN）对“溶剂插层-超声剥离”法制备的氟化石墨烯（GeF）进行液晶化改性（LC-GeF），再与本征导热液晶PI（LC-PI）基体复合制备LC-GeF/LC-PI导热复合膜。当LC-GeF导热填料的质量分数为15 wt%时，LC-GeF/LC-PI导热复合膜室温下的面内λ（λ∥）和面间λ（λ⊥）分别达到4.21 W/(m·K)和0.63 W/(m·K)，较普通PI膜的λ∥（0.77 W/(m·K)）和λ⊥（0.15 W/(m·K)）提升了446.8%和320.0%，较本征导热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导热复合膜。此外，相同填料用量下，LC-GeF/LC-PI复合膜还具有较GeF/LC-PI复合膜更加优异的绝缘性能、力学性能和热性能。
本文亮点
1. 利用非离子型表面活性剂TMN对GeF进行液晶化改性，基于TMN和GeF间氢键作用实现了LC-GeF导热填料的微观有序排列。
2. 当LC-GeF导热填料的质量分数为15 wt%时，LC-GeF/LC-PI导热复合膜室温下的λ∥和λ⊥分别达到4.21 W/(m·K)和0.63 W/(m·K)，较普通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导热复合膜具有优异的绝缘性能、力学性能和热性能，15 wt% LC-GeF/LC-PI导热复合膜的体积电阻率、杨氏模量、玻璃化转变温度和耐热指数分别为7.9×1014 Ω·cm、2.4 GPa、349.2oC和278.7oC，明显优于普通PI膜（1.4×1013 Ω·cm、1.4 GPa、332.8oC和266.6oC）。