Liquid Crystalline Polyimide Films with High Intrinsic Thermal Conductivities and Robust Toughness

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.