Blends of modified polypropylene (PP) with poly(R,S)‐β‐hydroxybutyrate (PHB) were prepared by casting polymer solutions, followed by compression molding into thin films. The modified polypropylene was obtained by oxidation with hydrogen peroxide. Oxidation of polypropylene produced new functional groups such as carbonyl and hydroxyl groups on the polymer chain, and a decrease in molecular weight and crystallinity of the polymers. Maximum crystallinity and mechanical properties of the polyblends were found with a PP/PHB ratio of 90/10 (w/w), and then decreased with increasing PHB content in the polyblends. Biodegradability of the polyblends was lower than that of bacterial and synthetic PHBs. Furthermore, an increase of PHB proportion in the polyblends resulted in highly non‐compatible polyblends. Hence only PHB and small parts of the polyblends were decomposed by microorganisms. Copyright © 2006 Society of Chemical Industry

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By first‐principles molecular dynamics, we have investigated the interaction of quartz (0001) surface with liquid water for two different fresh silica cleavages. The first type of cleavage is terminated by Si(O)2 and Si for two surfaces, respectively, whereas the second type cleavage has the same termination on both surfaces that consists of SiO. The water molecules were found to be decomposed and spontaneously form silanol group on both silica surfaces. After 4.0 ps, the chemical reactions were almost saturated. It was found that the silanol groups dominated on both surfaces. For the first type of cleavage, the final structure contains geminal, triple, and single silanols together with peroxy SiOOSi and SiOOH defects. For the second type of cleavage, the final structure contains geminal silanol, single silanol, and siloxane bridge. A small amount of unsaturated sites were also found on both surfaces. Further, we have shown that the newly formed rings at quartz surface range from four‐ to seven‐member ring for both surfaces. All the findings are in good consistent with the recent experimental observations and theoretical respects. © 2012 Wiley Periodicals, Inc.

The interfacial structure of heptane and toluene at oil-silica interfaces has previously been studied by sum frequency generation [Z. Yang et al., J. Phys. Chem. C. 113, 20355 (2009)]. It was found that the toluene molecule is almost perpendicular to the silica surface with a tilt angle of about 25°. Here, we have investigated the structural properties of toluene and heptane at oil-silica interfaces using molecular dynamics simulations for two different surfaces: the oxygen-bridging (hydrophobic) and hydroxyl-terminated (hydrophilic) surfaces of quartz (silica). Based on the density profile, it was found that both heptane and toluene oscillate on silica surfaces, with heptane showing more oscillation peaks. Furthermore, the toluene molecules of the first layer were found to have an asymmetric distribution of orientations, with more CH(3) groups pointed away from the silica surface than towards the silica surface. These findings are generally consistent with previous experiments, and reveal enhanced molecular structures of liquids at oil-silica interfaces.

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