Ordered Arrangements (ordered + arrangement)

Distribution by Scientific Domains

Selected Abstracts

ChemInform Abstract: Crystal Structure of Metastable ,-CeZrO4 Phase Possessing an Ordered Arrangement of Ce and Zr Ions.

CHEMINFORM, Issue 15 2001
Haruo Kishimoto
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Interaction of non-ionic hydrogels with weak aromatic acids

Krisztina László
Abstract Measurements are reported of the swelling behaviour at 20°C of poly (N isopropylacrylamide) (PNIPA) gels in aqueous solutions of two weak aromatic acids, phenol and resorcinol. For solute concentrations below 45 mmol/l the uptake of these solutions is similar. Due to selective solvation phenol exhibits an excess equilibrium concentration inside the gel of 5% over that in the surrounding bath, while for resorcinol, the excess is found to be 12%. At 50 mmol/l solute concentration, both systems display a volume transition accompanied by expulsion of the solvent. The solubility limits in water of these aromatic compounds, which are significantly different from each other (870 mmol/l and 9080 mmol/l respectively), are far above this critical concentration. In the collapsed condition the expelled liquid spreads on the surface of the phenol treated gel, while an ordered arrangement of separate droplets is generated in the case of resorcinol. In the latter case an acute contact angle was observed. It is also shown by acid-base titration that the PNIPA/water system may exhibit a slight ion exchanging character. [source]

New Polymeric Materials with Interferential Optical Properties

Leďla Ghannam
Abstract Nature provides a wide pallet of colors but also a wide number of fascinating optical phenomena such as nacre or interferential effects, which can be observed in insect wings and shellfish. The origin of such effects is attributed to the presence of highly ordered arrangements in Nature's materials. The aim of this paper is to focus some new approaches and advances for creating interferential optical phenomena as observed in nature by tuning or modeling the polymer architectures or organization. A relatively simple method is described to prepare organic/inorganic hybrid pigments constituted of mica platelets and adsorbed polymer layers. It is shown that the color of mica is changed upon polymer adsorption, and when one of the copolymer sequences includes a dye, its color is influenced by the chemical properties of the mica surface. Moreover, a new facile route is presented to obtain highly ordered surfaces using ionomer macromolecular designs synthesized in one step by controlled radical polymerization. The preparation of films with very regular pore size and spatial organization is successfully realized by using ionomer solutions. An original property of these films with an iridescent color obtained by light diffraction as a result of the optical interferences of sunlight with the periodic honeycomb structures is presented. All these new materials based on polymeric controlled structures can reproduce nature by creating an optical interferential and iridescent material, which offers new fascinating applications as original bio-mimetic materials on inorganic surfaces. [source]

Synthesis of Oligo(thienylfuran)s with Thiophene Rings at Both Ends and Their Structural, Electronic, and Field-Effect Properties

Yasuo Miyata Dr.
Abstract Oligo(thienylfuran)s with thiophene rings at both ends (SOSOSOS, DE-SOSOS, DH-SOSOS, DE-SOSOSOS, and DH-SOSOSOS; S and O denote thiophene and furan rings, respectively, DE and DH denote diethyl- and dihexyl-substituted, respectively) were newly synthesized by repetitive Stille coupling reactions. The UV/Vis maximum absorptions of the oligomers, SO, SOSO, SOSOS, SOSOSO, and SOSOSOS, exhibited a clear bathochromic shift with increasing number of heterocycles. The value of the oxidation peak potential (Epa1) determined by cyclic voltammetry decreased with an increase in the number of heterocycles by 0.06,0.08,V per heterocycle. The crystal-packing structures of DE-SOSOS and DH-SOSOS determined by X-ray crystallography have a herringbone motif and are denser than the reported structures of pentacene and ,-sexithiophene. The morphologies of thin films prepared by vacuum deposition and spin coating were investigated by atomic force microscopy and X-ray diffraction. Among these films, those of DE-SOSOS and DH-SOSOS exhibited highly ordered arrangements. The devices based on vacuum-deposited and spin-coated films of DE-SOSOS and DH-SOSOS displayed the highest FET mobilities of 10,2,10,3,cm2,V,1,s,1 among the oligomers reported in this study. [source]