Hybrid materials based on a new polyhedral oligomeric silsesquioxane, octa(2,3-epoxypropyl)silsesquioxane (OE) with diamines of 4,4'-methylenedianiline (DDM) and 5-trifluoromethyl-1,3-phenylenediamine (FPA) were prepared and characterized. OE was synthesized from cage-structured octaallylsilsesquioxane (OA) with m-chloroperbenzoicacid. The FTIR studies suggested that the N-H bond in diamines was not completely reacted with epoxy group due to steric hindrance and also extensive hydrogen bonding existed in the hybrid materials. The retention of the cage structure in the prepared hybrid materials was suggested by the FTIR and Si-29 NMR studies. The OE/FPA hybrid materials had superior thermal/mechanical characteristics than the OE/DDM due to the higher rigidity of the FPA than that of DDM or the silicon-fluorine interaction enhancing crosslinking reaction or hydrogen bonding. The prepared OE/FPA had a T-g of 170 degrees C, which was higher than diglycidyl ether of bisphenyl A (DGEBA)/DDM at the same stoichiometric ratio. It also had excellent thermal, mechanical, and dielectric characteristics with high storage modulus of 1.8 GPa (30 degrees C) and 0.3 GPa (250 degrees C), low coefficient of thermal expansion of 86 mu m/m degrees C, and dielectric constant of 2.19. Thus, it can be high performance materials with potential applications for electronic packaging. (c) 2005 Elsevier Ltd. All rights reserved.