2008 NOV 24 - (VerticalNews.com) -- According to a study from Athens, Greece, "In this work, yielding and post yielding effects are analyzed using the idea of the inhomogeneous distribution of strain in polymers under deformation. This idea is directly connected with the free volume concept, as created in the polymeric bulk during the frozen in process, and or the density fluctuations combined with other type defects."

  "A simple strain density distribution function is assumed, following experimental results available from techniques such as positron annihilation lifetime spectroscopy (PALS). Hereafter, a functional form of the rate of plastic deformation is extracted, which will be combined with a given kinematic formulation. The proposed analysis is tested with experimental data of polystyrene (PS) and PS/SiO2 nanocomposites. The incorporation of nanosized fillers into the polymeric bulk, strongly affects the free volume distribution and/or the distribution of defects related with density fluctuations. This fact is reflected in the model parameter values, and their variation in respect to the different material types," wrote G. Spathis and colleagues, National Technical University ...read more

  2008 NOV 24 - (VerticalNews.com) -- "Twelve novel poly(allylamine) (PAA)-based, comb-shaped amphiphilic polymers have been developed. Hydrophobic groups of cetyl, palmitoyl and cholesteryl were randomly grafted to PAA and quaternisation was carried out on some modified polymers," scientists in Scotland report.

  "Polymers were characterised using H-1 NMR, elemental analysis and differential scanning calorimetry. All polymers formed nano self-assemblies in the aqueous solution with a positive zeta potential and were able to encapsulate a hydrophobic agent, methyl orange, in the core. The critical aggregation concentration (CAC) and the microviscosity were found to be dependent on the polymer hydrophobicity. Being the most hydrophobic polymer, cholesteryl-grafted PAA had the lowest CAC (0.02 mg mL(-1)) and the highest microviscosity. They appeared to form dense nanoparticles and were transformed into novel nanostructures in the presence of free cholesterol. Palmitoyl-grafted polymers formed nanoparticles while cetyl-grafted polymers formed polymeric micelles," wrote C.J. Thompson and colleagues, Robert Gordon University ...read more

  2008 NOV 24 - (VerticalNews.com) -- According to recent research from Ningbo, People's Republic of China, "A sol-gel method has been proposed to prepare uniform TiO2 nanoparticles whose average size is about 30 nm. The prepared nanometer TiO2 particles are modified by acetamide via different self-assembled processes."

  "X-ray diffraction analyses, scanning electron microscopy, and Fourier transform infrared spectrometry are used to determine the structure of the nanoparticles. The results indicate that the different synthesis processes do not change the morphology of the TiO2/acetamide nanoparticles; nevertheless, they affect the interaction between amide and acetamide. The electrorheological (ER) activity is studied by shear stress under DC electric field. The acetamide-modified TiO2 ER fluid shows notable ER activity with shear stress about 45 kPa (at 5 kV/mm), which outclasses the shear stress (2 kPa) of unmodified TiO2 ER fluid. It is also found that the ER effect is very sensitive to the interaction of molecules on TiO2 particles," wrote Y.C. Cheng and colleagues ...read more