The influencing factors on the macroporous formation in polymer films by water droplet templating

Regular micrometer-size porous polystyrene film is prepared by water droplet templating, i.e. breath figures are stabilized by the polymer in solution and thermocapillary flow arranges them into ordered packing. The influences of polystyrene molecular weight, solvent properties, and the relative humidity of atmosphere on the pattern formation and hole sizes are investigated. Two different kinds of hole packing fashion are also observed and their formation mechanisms are discussed.

Surface modification of single-walled carbon nanotubes with polyethylene via in situ Ziegler-Natta polymerization

Single-walled carbon nanotubes (SWNTs) were modified with polyethylene (PE) prepared by in situ Ziegler-Natta polymerization. Because of the catalyst pre-treated on the surface of the SWNTs, the ethylene was expected to polymerize there. Scanning electron microscopy images and solubility measurements showed that the surface of the SWNTs was covered with a PE layer, and a crosslink may have formed between the SWNTs and PE. When the SWNTs covered with a PE layer were mixed with commercialized PE by melt blending, the resulting composite had better mechanical properties than the composite from the SWNTs without a PE layer. The yield strength, the tensile strength and modulus, the strain at break, and the fracture energy of the modified-SWNT/PE composites were improved by 25, 15.2, 25.4, 21, and 38% in comparison with those of the raw-SWNT/PE composites.

Investigation of sandwiched gadolinium(III) complexes with tungstosilicates as potential MRI contrast agents

Two gadolinium-sandwiched complexes with tungstosilicates, K-13[Gd(SiW11O39)(2)] (Gd(SiW11)(2)) and K11H6[Gd2O3(SiW9O34)(2)] (Gd-3(SiW9)(2)), have been investigated by in vitro and in vivo experiments as potential contrast agents for magnetic resonance imaging (MRI). T-1-relaxivity of Gd(SiW11)(2)was 6.59 mM(-1) . s(-1) in aqueous solution and 6.85 mM(-1) . s(-1) in 0.725 mmol . L-1 bovine serum albumin solution at 25degreesC and 9.39 T, respectively. The corresponding T-1-relaxivity of Gd-3(SiW9)(2) was 12.6 and 19.3 mM(-1) . s(-1) per Gd, respectively. MRI for Sprague-Dawley rats showed longer and more remarkable enhancement in rat liver after i.v. injection of these two complexes: 39.4 +/- 3.9% and 57.4 +/- 11.6% within the first 30 min after injection, 31.2 +/- 2.6% and 39.9 +/- 7.6% in the next 60 min for Gd(SiW11)(2) and Gd-3(SiW9)(2) at doses of 0.081 and 0.084 mmol Gd/kg, respectively. Our preliminary in vitro and in vivo study indicates that Gd(SiW11)(2) and Gd-3(SiW9)(2) are favorable candidates for hepatic contrast agents for MRI. However, the two complexes exhibit higher acute toxicity and need to be modified and studied further before clinical use.