Enhancement of thermal conducting properties in epoxy thermoset systems using an aligned liquid-crystalline mesophase

Abstract

Liquid crystalline epoxy resins (LCERs) with high thermal conductivity (T/C) are an attractive solution that meet the thermal management requirements of electronic devices. The ordered microstructure derived from LCs can improve heat dissipation in the polymer network by reducing phonon scattering. Here a series of LCE systems named EB-n is successfully developed by connecting two biphenyl mesogens with several aliphatic spacers (n). The EB-n monomers with even spacers (n = 4, 6, 8) exhibit a wide nematic phase range between 160 °C and 230 °C, while EB-7 shows a weak mesophase only during heating, indicating that the spacer length controls the LC properties and molecular ordering. The curing reaction repairs the network using symmetric and asymmetric aromatic diamines capable of reacting in an aligned LC state. The resulting products exhibit high T/C with values ranging between 0.519 and 0.757 W m⁻¹ K⁻¹, which are about three times higher than those of conventional thermosets, and superior thermal and mechanical properties. Moreover, thermal infrared imaging demonstrates that their high T/C has an apparent effect on heat dissipation. These results suggest that the LCE system has many potential applications in the high-performance electric device industry.