A series of aromatic diepoxides consisting of rigid ester unit with different lengths of flexible alkoxy side groups (R = H, OCH3, OC3H7, and OC8H17) were synthesized, and their thermal and cure behavior with aromatic diamine were investigated by using a DSC. The values of melting temperatures for the epoxy monomers ranged from 65 to 221degreesC depending upon the length of side groups. Cure kinetics of an epoxy/4,4'-diaminodiphenylmethane (DDM) system with two different side groups (R = OC3H7 and OC8H17) forming homogeneous mixture was examined using a multi-temperature scan method, developed by Ozawa and Kissinger, in order to determine the activation energy (E) and the frequency factor (A). The epoxy monomer having longer side group showed smaller E and larger A, indicating that the introduction of the long flexible side group could accelerate the cure reaction of rod-like epoxy.