Synthesis and characterization of a novel liquid-crystalline epoxy resin combining biphenyl and aromatic ester-type mesogenic units

A novel liquid-crystalline epoxy resin combining biphenyl and aromatic ester-type mesogenic units, diglycidyl ether of 4,4'-bis(4-hydroxybenzoyloxy)-3,3',5,5'-tetramethyl biphenyl, was synthesized. Its spectroscopic structure, thermal properties, and phase structures were investigated with NMR, differential scanning calorimetry (DSC), and polarized light microscopy (PLM), respectively. The curing agent, diaminodiphenylsulfone, was chosen to investigate the curing behavior by means of DSC and PLM during isothermal and nonisothermal processes. Only one exothermal peak appeared in the isothermal DSC curves. Birefringence was also observed during the curing processes and preserved after postcuring. Compared with short rigid-rod and flexible epoxies, the cured liquid-crystalline epoxy resin that was obtained displayed special thermal stability according to thermogravimetric analysis because of its long rigid-rod mesogenic unit and bulky methyl groups. (c) 2007 Wiley Periodicals, Inc.