A series of novel novolac epoxy resins containing naphthalene moiety with different molecular weights were synthesized via condensation of bisphenol A and 1-naphthaldehyde, followed by epoxidation with epichlorohydrin. The chemical structure of the naphthalene epoxy thus obtained was characterized using FTIR, H-1 NMR spectra and GPC analyses. The naphthalene epoxy was cured with 4,4'-diaminodiphenyl sulfone (DDS) and the cured products were characterized with thermogravimetric analysis, dynamic mechanical analysis, and X-ray diffraction. Compared with the diglycidyl ether of bisphenol A (DGEBA), the cured naphthalene epoxy resin showed remarkably higher glass transition temperatures (T(g)s), enhanced thermal stability and better moisture resistance. When the molar ratio of 1-naphthaldehyde to bisphenol A was 0.67, the optimal thermal resistance was observed. (C) 2007 Elsevier Ltd. All rights reserved.