Enhanced intrinsic thermal conductivity of liquid crystalline polyester through monomer structure optimization in main chains

Abstract

In order to investigate the influence of intermolecular interactions on polymer crystallization, a series of liquid crystal polyesters with high thermal conductivity (B-LCPs) were synthesized. These were synthesized using biphenyl diols and various dicarboxylic acids as raw materials, employing a “one pot” melt polycondensation method. The λ value of B-LCP4 reaches 0.462 W (m K)⁻¹, marking an enhancement of 135.8% in comparison to that of B-LCP3, which is 2.3 times greater than that of traditional thermoplastics. The diffraction peak of B-LCP4 at 2θ = 27.4° indicates the formation of a π–π stacking structure and crystallinity around 58%. B-LCP4 exhibited significant melting peaks and weak cold crystallization during the second heating scan, which indicates the crystal phase becomes more integrated and regular. Furthermore, the T_5%, T_max and residual carbon at 800 °C of B-LCP4 were 387.7 °C, 422.2 °C and 15.4%, respectively. The augmented thermal stability of B-LCP4 is ascribed to the delocalization of π-electrons along the backbone, which facilitates a planar conformation. The findings indicate that the π–π stacking interaction can enhance the crystallinity of polymers, subsequently improving their thermal conductivity.