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

Low intrinsic thermal conductivity coefficients (lambda) 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 similar to 388 degrees C, including curing temperature of 350 degrees C. The LC-PIIV films cured in liquid crystal range retain liquid crystal texture to room temperature, and the in-plane lambda(lambda(parallel to)) and through-plane lambda (lambda(perpendicular to)) at room temperature reach 2.11 W/(m.K) and 0.32 W/(m.K), respectively, significantly higher than lambda(parallel to) (0.77 W/(m.K)) and lambda(perpendicular to) (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.