The application of nanotechnology to thin film nanocomposites (TFN) is a new route to enhance membrane performance in water desalination. Here, the potential of polyhedral oligomeric silsesquioxane (POSS) as the nanofiller in polyamide (PA) reverse osmosis membranes was systematically investigated. Four POSS materials (P-8Phenyl, P-8NH(3)Cl, P-8NH(2) and P-1NH(2)) were introduced into the selective layer by physical blending or chemical fixation during standard interfacial polymerization. Water flux and NaCl rejection were measured with 2000 ppm NaCl solution under 15.5 bar pressure, and SEM and TEM images of membrane selective layers were obtained. Membranes prepared without POSS showed water flux of 20.0 +/- 0.5 L/m(2).h and salt rejection of 98.0 +/- 0.2%. TFN membranes prepared with 0.4% (w/v) P-8Phenyl in the organic phase showed a 65% increase in water flux compared to the pristine PA membrane while maintaining high salt rejection. The selective layer of this membrane maintained the typical ridge-and-valley structure of aromatic PA. Results with P-8NH(3)Cl and P-8NH(2) added to the organic phase were similar. TFN membranes prepared with monoamine P-1NH(2) in the organic phase had poor water flux of 3.2 L/m(2).h, a smooth and more hydrophobic surface, and a much thicker (similar to 400 nm) selective layer. One of the four POSS compounds studied. P-8NH(3)Cl, is sufficiently soluble in water for incorporation into the selective layer via the aqueous phase. Membranes were prepared with P-8NH(3)Cl in the aqueous phase at varying reaction Lime, loading, and additive (triethylamine) concentration. With these parameters optimized, water flux increased to 35.4 L/m(2).h. (C) 2014 Elsevier B.V. All rights reserved.