High thermal conductivity and excellent mechanical properties of liquid crystal co‐polyester based on hydron bond

Abstract

AbstractHigh thermal conductivity liquid crystal polymer has become a hot topic in electronic device research. Herein, we introduce a series of thermotropic liquid crystals synthesized by diphenyl diol, m‐phthalic acid, and 5‐hydroxyisophthalic acid. The intermolecular forces are tuned by adjusting the ratio (0, 20%, 40%, 60%, 80%, 100%) of monomers containing hydrogen bond donors in copolymers. The formation and dissociation of hydrogen bonds are analyzed from the red shift and blue shift of infrared spectra at variable temperatures. The thermal conductivity is increased to 0.31 Wm−1 k−1. Meanwhile, its mechanical properties and thermal stability have improved significantly. A sharp increment of 2120% in tensile strength was observed, the maximum tensile strength is 17.39 MPa. While Young's modulus increased from 0.26 to 1.224 GPa. The increase in intermolecular forces is the main reason for this result. Moreover,X‐raysingle‐crystal diffraction, polarizing microscope, differential scanning calorimetry, and thermogravimetric analysis (TGA) were also analyzed to further explore the thermal conduction mechanism. The formation of hydrogen bonds makes the linear polymer chain segments undergo reversible cross‐linking, which affects their crystallization behavior and provides more thermal conduction pathways. By controlling the number of hydrogen bond donors to control the cross‐linking density, the thermal conductivity and mechanical properties can be greatly improved.