Phototransformations of some 3-alkoxy-2-styrylchromones: type II cyclisations of 1,4- and 1,6-biradicals

3-Alkoxy-2-styrylchromones on photo-irradiation with UV-light transform into oxetanopyrananones, pyranopyrones, pyranopyrananones and pyranoalcohols. The products formed have been found to depend upon the structure of alkoxy group (methyl, benzyl and allyls). Alkoxychromones containing a heterocyclic ring (thiophene, furan) in place of phenyl in the styryl group produced only pyranoalcohols as the photoproducts. The photo-conversions have been rationalized through an initial H-abstraction by the CO group producing a 1,4-biradical. In allyloxy derivatives, cyclisations involve both 1,4- and 1,6-biradicals.     

Preparation and Characterization of Porous Titania by Modified Sol-Gel Method

Mesoporous titania, especially anatase, is attractive due to its potential applications. A novel method to control pore structure of titania, surfactant- or polymer modification, is proposed. The wet gels and gel films, prepared from Ti(O-nC₄H₉)₄ were dried at 90°C and annealed at 500°C after immersion in surfactant or polymer solutions, and mesoporous anatase was obtained. The pore size, pore volume and specific surface area of the surfactant-modified bulk gels, estimated from N₂ absorption-desorption curves, are more than twice larger than those of the gels without modification. The pore size of the surfactant-modified gel films, observed by SEM, are similar to that of the bulk gels. The pore size obviously depended on the size of micelles. The pore size of the gels modified with hydrophilic polymers hardly increased, but the pore volume and the specific surface area increased.     

Applications of nuclear methods in the automotive industry

Over the years nuclear methods have proved to be a valuable asset to industry in general and to the automotive industry in particular. This paper summarizes some of the most important recent contributions of nuclear technology to the development of vehicles having high quality and long-term durability. Radiotracer methods are used to measure engine oil consumption and the wear rates of inaccessible components. Radiographic and tomographic methods are used to image fluids and structures in engines and accessory components. Tracers are used to understand combustion chemistry and quantify fluid flow. Gauging methods are used for inspection and process control. Nuclear analytical methods are used routinely for materials characterization and problem solving. Although nuclear methods are usually considered as the means of last resort, they can often be applied more easily and quickly than conventional methods when those in industrial engineering and R&D are aware of their unique capabilities.     

Evaluation of Two-center One- and Two-electron Integrals over Slater Type Orbitals

A formulation previously presented by the authors for coulomb integrals was generalized to other two-center integrals, except exchange integral. Within this frame, molecular integrals were expressed in terms of some new functions closely related to the well-known incomplete gamma functions and these functions recursively evaluated. Special issues arising in the case of hybrid integrals were addressed, and the results were compared with the ones found in the literature.     

Synthesis and characterization of polymeric linseed oil grafted methyl methacrylate or styrene

Syntheses of wholly natural polymeric linseed oil (PLO) containing peroxide groups have been reported. Peroxidation, epoxidation and/or perepoxidation reactions of linseed oil, either under air or under oxygen flow at room temperature, resulted in polymeric peroxides, PLO-air and PLO-ofl, containing 1.3 and 3.5 wt.-% of peroxide, with molecular weights of 2 100 and 3 780 Da, respectively. PLO-air contained cross-linked film up to 46.1 wt.-% after a reaction time of 60 d, associated with a waxy, soluble part (PLO-air-s) that was isolated with chloroform extraction. PLO-ofl was obtained as a waxy, viscous liquid without any cross-linked part at the end of 24 d under visible irradiation and oxygen flow. Polymeric peroxides, PLO-air-s and PLO-ofl initiated the free radical polymerization of both methyl methacrylate (MMA) and styrene (S) to give PMMA-graft-PLO and PS-graft-PLO graft copolymers in high yields with Mw varying from 37 to 470 kDa. The polymers obtained were characterized by FT-IR, (1)H NMR, TGA, DSC and GPC techniques. Cross-linked polymers were also studied by means of swelling measurements. PMMA-graft-PLO graft copolymer film samples were also used in cell-culture studies. Fibroblast cells were well adhered and proliferated on the copolymer film surfaces, which is important in tissue engineering.     

Synthesis of block copolymers by the transformation of cationic polymerization into reversible atom transfer radical polymerization

Azo-containing polytetrahydrofuran (PTHF) obtained by cationic polymerization was used as a macroinitiator in the reverse atom transfer radical polymerization (RATRP) of styrene and methyl acrylate in conjunction with CuCl₂/2,2′-bipyridine as a catalyst. Diblock PTHF–polystyrene and PTHF–poly(methyl acrylate) were obtained after a two-step process. In the first step of the reaction, stable chlorine-end-capped PTHF was formed with the thermolysis of azo-linked PTHF at 65–70 °C in the presence of the catalyst. Heating the system at temperatures of 100–110 °C started the polymerization of the second monomer, which resulted in the formation of block copolymers. The decomposition behavior of the azo-linked PTHF and the structure of the block copolymers were determined by ¹H NMR and gel permeation chromatography (GPC). Kinetic studies and GPC analyses further confirmed the controlled/living nature of the RATRP initiated by the polymeric radicals. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2199–2208, 2002     

trans‐Bis­[O‐2,4‐di‐tert‐butyl­phenyl (4‐methoxy­phenyl)­di­thio­phosphonato‐κ2S,S′]­nickel(II)

In the the title compound, [Ni(C₂₁H₂₈O₂PS₂)₂], the Ni atom resides on an inversion centre and is coordinated in a square‐planar array by four S atoms, with Ni—S and P—S bond lengths of 2.2336 (12)/2.2351 (13) and 1.9910 (16)/2.0010 (17) Å, respectively. The two O‐2,4‐di‐tert‐butyl­phenyl and two 4‐methoxy­phenyl moieties adopt trans configurations about the central Ni atom.     

Synthesis and morphological characterization of poly(ϵ-caprolactone) and poly(2-methyloxazoline) substituted phenyl rings and phenylene oligomers

Poly(ϵ-caprolactone) (PCL) and poly(2-methyloxazoline) (POx) substituted phenyl rings (macromonomers) and the corresponding substituted polyphenylene oligomers have been synthesized in various chemical structures. Macromonomers were synthesized by ring opening polymerization. Poly(phenylene) oligomers were then synthesized by cross-coupling of the macromonomers in Ni-catalyzed polycondensation reactions. The macromonomers and oligomers have been characterized by ¹H-NMR, IR, GPC, and DSC. The effect of side chain chemistry and architecture on the resulting morphology in thin films has been investigated by atomic force micro-scopy and wide angle X-ray scattering. Polyphenylene oligomers showed layered morphologies in thin films. The orientation of the layers depended on the chemistry of the side chains and the backbone architecture. Linear oligomers containing statistically distributed segments having POx or PCL side chains showed layers perpendicular to the underlying substrate. Attachment of polystyrene end block to PCL chain together with the meta-connectivity of the backbone resulted in layers parallel to the substrate. Our results also indicate that substitution of polymeric chains to phenyl rings can induce ordered structures of macromonomers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2091–2104, 2007     

Improving the detection limit of silicon, magnesium and aluminum in neutron activation analysis of polymers using a TRIGA? reactor

The measurement of impurities, specifically; the combination of magnesium, silicon and aluminum, in polymers and in mixed additives is a common problem for industrial application of neutron activation analysis (NAA). Typically this problem can be addressed using XRF and ICP. However, in some cases, the available sample size, desired detection limit and the desired accuracy prohibit the use of XRF or ICP. Therefore under these requirements, as in the measurement of talc in milligram size polymer fibers, using NAA has become a niche for nuclear analytical applications. Other important advantages, apart from high precision and lower detection limit, are the non-destructive nature of the analysis and the minimal sample preparation necessary to carry out the measurement. Therefore, polymers such as polyethylene, polystyrene or poly-carbonate can be analyzed for these metals as organic solutions, beads, films, pellets or powders. This paper highlights some of the recent improvements made to the Dow NAA measurement facility to accomplish this task.