Liquid Crystalline Polyimide Films with High Intrinsic Thermal Conductivities and Robust Toughness
Kunpeng Ruan, Yongqiang Guo, Junwei Gu
Abstract
Low intrinsic thermal conductivity coefficients (λ) of polyimide (PI) films limit their application in heat-prone flexible electronics. By optimizing the liquid crystal range to fit the curing temperature, novel kinds of intrinsically highly thermally conductive liquid crystalline PI (LC-PI) films are fabricated. When the molar ratio of 4,4′-diaminodiphenyl ether (ODA) to 1, 4-bis(4-aminophenoxy)benzene (TPE-Q) is 1:3 (sample no. IV), liquid crystal range of preLC-PIIV films is 272∼388 °C, including curing temperature of 350 °C. The LC-PIIV films cured in liquid crystal range retain liquid crystal texture to room temperature, and the in-plane λ (λ∥) and through-plane λ (λ⊥) at room temperature reach 2.11 W/(m·K) and 0.32 W/(m·K), respectively, significantly higher than λ∥ (0.77 W/(m·K)) and λ⊥ (0.15 W/(m·K)) of LC-PII films which are cured out of the liquid crystal range. Meanwhile, LC-PIIV films possess excellent mechanical and thermal properties, showing application prospects in high-heating flexible electronics.