With the aim of selecting a precursor of a polyhedral oligomeric silsesquioxane (POSS) reacted with aromatic diamines for its incorporation into an epoxy network, to generate an organic-inorganic hybrid material containing POSS, a polyhedral oligomeric silsesquioxane (glycidylisobutyl-POSS) was reacted with the diamines 4,4'-methylenebis(2,6-diethylaniline) (MDEA), 4,4'-diaminediphenylmethane (DDM), and 4,4'-(1,3-phenylenediisopropylidene)bisandine (BSA), at 160degreesC and different times, in a proportion rich in amines. The distribution of species in the reaction was followed by gel permeation chromatography (GPC). From the experimental data obtained the selected precursor was POSS/BSA reacted at 160degreesC for 20 or 30 min, to ensure that all the POSS was reacted, that there was a maximum of the monosubstituted amines, and that there was no degradation. (C) 2004 Wiley Periodicals, Inc.