Polyurethane networks modified with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane

OpePOSS was incorporated into polyurethane to make organic-inorganic hybrid composites and nano-composites containing up to 20 wt.-% POSS were prepared. The formation of the hybrid polyurethane networks is ascribed to two principal cross-linking reactions: i) the cross-linking 1 reaction between MOCA and the polyurethane prepolymer and ii) the inter-component reaction between the PU networks and OpePOSS. The latter was confirmed by model compound reactions. TEM indicates that the POSS was homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the nanocomposites displayed increased glass transition temperatures compared to the control polyurethane. In terms of TGA, the nanocomposites displayed improved thermal stability. Tensile tests indicate that the organic-inorganic hybrid networks were significantly reinforced with the inclusion of POSS. Contact angle measurements show that the organic-inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity as well as a reduction in the surface free energy. The improvement in surface properties was ascribed to the presence of the POSS moiety in place of the polar component of polyurethane. XPS shows enrichment with Si-containing moieties on the surfaces.