Heteropolyacid/saponite-like clay complexes and their blends in amphiphilic SEBS

A synthetic saponite-like clay, Sumecton SA (SSA), was self-assembled with 12-phosphotungstic acid (PTA) heteropolyacid for the preparation of new hybrid nanocomposites for proton exchange membranes. Thermogravimetric analysis (TGA) and Fourier transformed diffuse reflectance spectroscopy (DRIFT) measurements indicate the formation of robust PTA-SSA complexes. The Keggin structure of PTA is preserved within the complexes and is thermally stable up to 450 degrees C. The amount of PTA incorporated into the clay depends on the PTA-SSA weight ratio used for the complex preparation. PTA incorporation achieved is approximately 2-3 times the PTA content of most reported literature. However, higher PTA incorporation is accompanied by a significant loss of structural clay integrity. Low PTA-SSA weight ratios tend to preserve clay structure, but do not preclude its general amorphization generated by the PTA acidic treatment. PTA-SSA complexes present a low degree of order. Inorganic complexes were blended by melt extrusion with chemically-modified styrene/ethylene-co-butylene/styrene block copolymer (SEBS). Poly(oxyethylene/oxypropylene)-grafted-SEBS is more efficient than maleic anhydride-grafted-SEBS at dispersing PTA-SSA complexes. For both nanocomposite systems, nanoparticles' size varies between 30 and 300 nm. (C) 2009 Elsevier Ltd. All rights reserved.