Phase Structure and Thermal Conductivity of Liquid Crystalline Epoxy Resins Cured with the Binary Mixed Curing Agents

Abstract

Liquid crystalline (LC) epoxy resin containing rigid mesogenic units (DGETAM) was prepared by curing with the binary mixed curing agent with different chemical structures, m-phenylenediamine (m-PDA) and 4, 4’-bis (4-aminobenzoyloxy) dodecane (12BAB). We determined the optimal composition ratio in binary mixed curing agent in order to form highly ordered network structure during the crosslinking reaction. The analysis of LC phase structure reveals that the DGETAM/m-PDA/12BAB_20 mol% system forms larger size of LC domain structure with highly ordered smectic phase. In the laser flash method, the value of thermal conductivity in DGETAM/m-PDA/12BAB_20 mol% system(0.31 W/(m･K)) is slightly higher compared to those of the other systems(0.27－0.30 (W/(m･K))). However, the thermal conductive map which was drawn by the periodic heating radiation-temperature measuring method showed a clear distribution of thermal conductivity in the cured resin. These results suggest that the effective phonon conductivity may be suppressed by the presence of locally low thermal conductive regions in DGETAM/m-PDA/12BAB_20 mol% system.