Thermal properties and cure kinetics of a liquid crystalline epoxy resin with biphenyl-aromatic ester mesogen

A liquid crystalline epoxy resin diglycidyl ether of 3,3′,5,5′-tetramethylbiphenyl-4,4′-diyl bis(4-hydroxybenzoate) (DGE-TMBPBHB) was synthesized and its thermal properties were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Thermal history markedly affected liquid crystalline (LC) phase behaviors. The peak values of the isotropized temperature (Ti), crystallized temperature (Tc) and enthalpy change (ΔHi) caused by the transition from the LC phase to the isotropic state of DGE-TMBPBHB decreased slightly during repetitive heat–cool cycles. Two liquid crystalline thermosets were prepared based on the epoxy monomer with two different curing agents, 4,4′-diaminodiphenyl methane (DDM) and 4,4′-diaminodiphenyl sulfone (DDS), respectively. Cure kinetics of mixtures of DGE-TMBPBHB/DDM and DGE-TMBPBHB/DDS were investigated by DSC under nonisothermal processes.