Novel Triaromatic Ester Mesogenic Liquid Crystalline Epoxy Resin Containing Both Methyl Substituent and Ethoxy Flexible Spacer: Synthesis and Curing

Abstract

A novel triaromatic ester liquid crystalline epoxy resin (LCER) that contains both a methyl substituent and an ethoxy flexible spacer, p‐methylphenylene di{4‐[(2,3‐epoxypropoxy)ethoxy]benzoate} (MPEPEB), has been synthesized. The mesotropic property has been investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (POM). MPEPEB shows a lower melting temperature at 78.7 °C and a broad nematic mesophase temperature range of about 55 °C. Meanwhile MPEPEB shows a mesophase to −50 °C upon cooling. The curing behavior of MPEPEB with 2,6‐diamino‐3,5‐diethyltoluene (DAE) has been investigated by means of DSC and POM during isothermal and dynamic processes. Although there is little difference between the activation energies obtained from the kinetic data, a marked difference is found between the isothermal and dynamic investigation. The curing reaction in the isothermal investigation roughly obeys n‐th order kinetics, while two exothermal peaks appear in the dynamic DSC curves of MPEPEB/DAE. A comparison of the isothermal and dynamic data shows that the curing rate is not a unique function of temperature and curing degree. The cured networks have lower glass temperatures and show a mesophase at room temperature which disappears at about 86–88 °C.magnified image

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