The control epoxy resin, CE (i.e., without modified), containing naphthalene group was synthesized directly from 1,6-dihydroxynaphthalene with epichlorohydrin and a stoichiometric of NaOH. The MDI (4,4'-diphenylmethane diisocyanate)-modified epoxy resins, ME, were prepared from the direct process, MDI with CE. Subsequently, they were cured from various composition of ME/CE with 4,4'-diaminodiphenylsulfone (DDS) and tetramethyl bisphenol F dicyanate (TBFD) in equal equivalent, respectively. In addition, the cure reaction was studied through a cross-reference between in situ Fourier transform infrared and DSC (differential scanning calorimeter) dynamic scanning. The kinetic model gives a good description of curing paths. The modified epoxy systems had higher activation energy than that of control epoxy resin. The epoxy resins with 10 wt % ME-modified was found to obtain appropriate result in combination with optimum properties and content (e.g., thermal stability, glass-transition temperature, coefficient of thermal expansion, moisture absorption, dielectric constant, and modulus etc.), which may be attributed to the naphthalene, oxazolidinone structure, and crosslink density contributed to optimal state in polymer matrices. Furthermore, the intermolecular interaction hydrogen bonding of, interpenetrating polymer networks. (c) 2006 Wiley Periodicals, Inc.