Synthesis and characterization of a POSS-maleimide precursor for hybrid nanocomposites

Epoxy polyhedral oligomeric silsesquioxane (POSS)-based hybrid nanocomposites were prepared by in situ polymerization of a homogeneous blend of the diglycidylether of bisphenol-A and 4,4'-diaminodiphenylmethane (DDM) in the presence of octa(maleimidophenyl) silsesquioxane. The reaction of a maleimido-functionalized POSS cube with the epoxy resin was studied by Fourier transform infrared analysis and the formation of nanocomposites was confirmed by wide-angle X-ray diffraction and scanning electron microscopy. Dynamic mechanical analysis studies indicated that the crosslinking structures of the nanocomposite networks were predominantly formed between the terminalmaleimide double bonds and the amino groups of DDMthrough a Michael addition reaction to form an aspartimide. The values of the glass transition temperatures (T-g) decreased with increasing POSS-maleimide content and this was likely to be due to the inclusion of POSS cages into the system and the consequent increase in free volume. The dynamic thermal stability of the cured polymers was increased by increasing the POSS content in the hybrid epoxy matrices as evidenced from thermogravimetric analysis data.