A technique was developed for preparing poly(dimethylsiloxane) nanocomposites having unusually high transparencies as quantitatively judged by ultraviolet–visible spectroscopy. The method was the in situ generation of silica particles by a two‐step sol–gel procedure in which the required water of hydrolysis was simply absorbed from the air, and the catalyst was generated in situ from a tin salt. Electron microscopy showed that the phase‐separated silica domains were very small (30–50 nm in diameter) and well dispersed, as expected from the transparency of the composites. Stress‐strain measurements in tension indicated that the particles provide very good reinforcement. Ultra‐small‐angle X‐ray scattering data showed that the domain morphology depends strongly on catalyst, but weakly on loading level. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1897–1901, 2003

Polypropylene (PP) was prepared by metallocene catalysts so as to have a stereoblock structure, with isotactic sequences long enough to give crystallites functioning as crosslinks, but small enough in number to have the atactic chains predominate in a surrounding elastomeric matrix. The resulting thermoplastic elastomer was then blended with organically modified clays to document the conditions required to exfoliate the clay layers in a way to maximize the chances for good reinforcement. Some experiments included the use of modified PP as a compatibilizing agent or a commercial silica, for reference purposes. The clays were clearly superior to the silica, which was found to be ineffective for reinforcing this elastomer. The nanoclay fillers did provide improvements in modulus but not toughness, because of corresponding decreases in extensibility. Resistance to creep also remained a problem, presumably due to the clay layers interfering with the growth of the crystallites needed to form a robust network structure. Copyright © 2004 Society of Chemical Industry

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Magnetic nanoparticles were created in or around the sulfonated (s) polystyrene domains in a poly[styrene-b-(ethylene-co-butylene)-b-styrene)] block copolymer (BCP) using an in situ inorganic precipitation procedure. The sBCP was neutralized with a mixed iron/cobalt chloride electrolyte, and the doped samples were converted to their oxides by reaction with sodium hydroxide. Transmission electron microscopy indicated the presence of nanoparticles having diameters of 20-50 nm. Metal oxide particle structures were studied using wide angle X-ray diffraction, which revealed that they were inverse spinel cobalt iron oxide crystals. Thermogravimetric analysis provided the weight percent of the inorganic component and nanocomposite thermal decomposition profile. Modulated differential scanning calorimetry studies suggested that the inorganic inclusions were selectively grown in the polystyrene hard block phase. These nanocomposites were shown, using alternating gradient magnetometry, to be ferrimagnetic at room temperature.

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