Reaction kinetics of liquid crystalline epoxy cured with aromatic diamine: Its synthesis and mechanical and electrical characteristics

The effect of the molar ratio of diglycidyl ether of 4,4 ' -biphenyl (DGEBP) to p-phenylene diamine (PDA) on the cure reaction rate was studied by the Kissinger and isoconversional equations. The cure mechanism was studied by FTIR analysis and the liquid crystalline phase structure was analyzed by wide angle X-ray diffraction (WAXD). With an increasing molar ratio of DGEBP/PDA, the preexponential factor was increased by the increasing collision probability between epoxide groups and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of rigid rodlike mesogen and the high crosslink density, which hindered the diffusion of functional groups. The activation energies obtained from the Kissinger equation were in good agreement with average values obtained from the isoconversional equation. The WAXD pattern showed a smectic layer structure with a layer thickness of 15.3 Angstrom and an intermolecular distance of 4.3 Angstrom. (C) 2001 John Wiley & Sons, Inc.