Graft copolymers prepared by ethoxylation of polyamide 12 and poly(ethylene-co-vinyl alcohol)

Graft copolymers consisting of polyamide 12 or poly(ethylene-co-vinyl alcohol) as backbone polymers and side chains of poly(ethylene oxide) have been synthesized. The amide and hydroxyl groups of the backbone polymers were used as initiation sites for the polymerization of ethylene oxide (EO). Potassium tert-butoxide was used for ionization of the active groups, and the polymerization of EO was carried out in dimethyl sulfoxide. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, ¹H-NMR, gel permeation chromatography, and FTIR. The size of the side chains varied between 300 and 1000 g/mol. Thermal properties were examined by DSC. The graft copolymers showed increasing crystallinity and increasing melt temperature with increasing molecular weight of the side chains. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 803–811, 1998     

Hexa­aqua­bis­(di­methyl sulfoxide)­yttrium(III) trichloride

The title compound, [Y(C₂H₆OS)₂(H₂O)₆]Cl₃, contains the cation [Y(H₂O)₆{(CH₃)₂SO}₂]³⁺ with a distorted square antiprismatic geometry of the eight coordinated O atoms. The six water mol­ecules are coordinated with an average Y—O distance of 2.38 (2) Å, ranging from 2.360 (3) to 2.404 (3) Å. Each water mol­ecule forms two hydrogen bonds to the chloride anions with O—Cl distances ranging from 3.068 (4) to 3.422 (4) Å. The two di­methyl­ sulfoxide ligands, situated in the cis position with the O—Y—O angle equal to 83.22 (11)°, have Y—O distances of 2.269 (3) and 2.278 (3) Å.     

Copoly(arylene ether nitrile) and copoly(arylene ether sulfone) ionomers with pendant sulfobenzoyl groups for proton conducting fuel cell membranes

Three series of fully aromatic ionomers with naphthalene moieties and pendant sulfobenzoyl side chains were prepared via K₂CO₃ mediated nucleophilic aromatic substitution reactions. The first series consisted of poly(arylene ether)s prepared by polycondensations of 2,6‐difluoro‐2′‐sulfobenzophenone (DFSBP) and 2,6‐dihydroxynaphthalene or 2,7‐dihydroxynaphthalene (2,7‐DHN). In the second series, copoly(arylene ether nitrile)s with different ion‐exchange capacities (IECs) were prepared by polycondensations of DFSBP, 2,6‐difluorobenzonitrile (DFBN), and 2,7‐DHN. In the third series, bis(4‐fluorophenyl)sulfone was used instead of DFBN to prepare copoly(arylene ether sulfone)s. Thus, all the ionomers had sulfonic acid units placed in stable positions close to the electron withdrawing ketone link of the side chains. Mechanically strong proton‐exchange membranes with IECs between 1.1 and 2.3 meq g⁻¹ were cast from dimethylsulfoxide solutions. High thermal stability was indicted by high degradation temperatures between 266 and 287 °C (1 °C min⁻¹ under air) and high glass transition temperatures between 245 and 306 °C, depending on the IEC. The copolymer membranes reached proton conductivities of 0.3 S cm⁻¹ under fully humidified conditions. At IECs above ∼1.6 meq g⁻¹, the copolymer membranes reached higher proton conductivities than Nafion^® in the range between −20 and 120 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Fully Aromatic Block Copolymers for Fuel Cell Membranes with Densely Sulfonated Nanophase Domains

Two multiblock copoly(arylene ether sulfone)s with similar block lengths and ion exchange capacities (IECs) were prepared by a coupling reaction between a non‐sulfonated precursor block and a highly sulfonated precursor block containing either fully disulfonated diarylsulfone or fully tetrasulfonated tetraaryldisulfone segments. The latter two precursor blocks were sulfonated via lithiation‐sulfination reactions whereby the sulfonic acid groups were exclusively placed in ortho positions to the many sulfone bridges, giving these blocks IECs of 4.1 and 4.6 meq·g⁻¹, respectively. Copolymer membranes with IECs of 1.4 meq·g⁻¹ displayed well‐connected hydrophilic nanophase domains and had decomposition temperatures at, or above, 300 °C under air. The copolymer with the tetrasulfonated tetraaryldisulfone segments showed a proton conductivity of 0.13 S·cm⁻¹ at 80 °C under fully humidified conditions, and surpassed that of a perfluorosulfonic acid membrane (NRE212) by a factor of 5 at –20 °C over time.

     

Determination of vitamin B12 in infant formula and adult nutritionals by liquid chromatography/UV detection with immunoaffinity extraction: First Action 2011.08

At the "Standards Development and International Harmonization: AOAC INTERNATIONAL Mid-Year Meeting," on June 29, 2011, an Expert Review Panel agreed that the method "Determination of Vitamin B12 in Infant Formulas and Adult Nutritionals by Liquid Chromatography/UV Detection with Immunoaffinity Extraction" be adopted AOAC Official First Action status. The method is applicable for the determination of vitamin B12, which includes added cyanocobalamin and natural forms, making it applicable to both fortified and nonfortified products. Vitamin B12 is extracted from the sample in sodium acetate buffer in the presence of sodium cyanide (100 degrees C, 30 min). After purification and concentration with an immunoaffinity column, vitamin B12 is determined by LC with UV detection (361 nm). A single-laboratory validation study was conducted on a range of products, including milk- and soy-based infant formulas, cereals, cocoa beverages, health care products, and polyvitamin premixes. The method demonstrated linear response over a large range of concentrations, recovery rates of 100.8 +/- 7.5% (average +/- SD), repeatability RSD (RSDr) of 2.1%, and intermediate reproducibility (RSD(iR)) of 4.3%. LOD and LOQ values were 0.10 and 0.30 microg/100 g, respectively, and correlation with the reference microbiological assay was good (R2 = 0.9442). The results of the study were published in J. AOAC Int. 91, 786-793 (2008). The performance characteristics of the method met the standard method performance requirements set forth by the Stakeholder Panel on Infant Formula and Adult Nutritionals; thus, the method was determined to be appropriate for First Action status.     

Intramolecular Gas‐Phase Reactions of Synthetic Nonheme Oxoiron(IV) Ions: Proximity and Spin‐State Reactivity Rules

The intramolecular gas‐phase reactivity of four oxoiron(IV) complexes supported by tetradentate N₄ ligands ( L ) has been studied by means of tandem mass spectrometry measurements in which the gas‐phase ions [Fe^IV(O)( L )(OTf)]⁺ (OTf=trifluoromethanesulfonate) and [Fe^IV(O)( L )]²⁺ were isolated and then allowed to fragment by collision‐induced decay (CID). CID fragmentation of cations derived from oxoiron(IV) complexes of 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane (tmc) and N,N′‐bis(2‐pyridylmethyl)‐1,5‐diazacyclooctane ( L ⁸Py₂) afforded the same predominant products irrespective of whether they were hexacoordinate or pentacoordinate. These products resulted from the loss of water by dehydrogenation of ethylene or propylene linkers on the tetradentate ligand. In contrast, CID fragmentation of ions derived from oxoiron(IV) complexes of linear tetradentate ligands N,N′‐bis(2‐pyridylmethyl)‐1,2‐diaminoethane (bpmen) and N,N′‐bis(2‐pyridylmethyl)‐1,3‐diaminopropane (bpmpn) showed predominant oxidative N‐dealkylation for the hexacoordinate [Fe^IV(O)( L )(OTf)]⁺ cations and predominant dehydrogenation of the diaminoethane/propane backbone for the pentacoordinate [Fe^IV(O)( L )]²⁺ cations. DFT calculations on [Fe^IV(O)(bpmen)] ions showed that the experimentally observed preference for oxidative N‐dealkylation versus dehydrogenation of the diaminoethane linker for the hexa‐ and pentacoordinate ions, respectively, is dictated by the proximity of the target C? H bond to the oxoiron(IV) moiety and the reactive spin state. Therefore, there must be a difference in ligand topology between the two ions. More importantly, despite the constraints on the geometries of the TS that prohibit the usual upright σ trajectory and prevent optimal σ_CH–σ* overlap, all the reactions still proceed preferentially on the quintet (S=2) state surface, which increases the number of exchange interactions in the d block of iron and leads thereby to exchange enhanced reactivity (EER). As such, EER is responsible for the dominance of the S=2 reactions for both hexa‐ and pentacoordinate complexes.     

The Mendelsohn Triple Systems of Order 13

A triple cyclically contains the ordered pairs , , , and no others. A Mendelsohn triple system of order v, or , is a set V together with a collection of ordered triples of distinct elements from V, such that and each ordered pair with is cyclically contained in exactly λ ordered triples. By means of a computer search, we classify all Mendelsohn triple systems of order 13 with ; there are 6 855 400 653 equivalence classes of such systems.     

Computer search for small complete caps

A computer search method for finding small complete caps inPG(d,q) is considered. The problem is formulated as a combinatorial optimization problem to which record-to-record travel, a stochastic local search method, is applied. Several new complete caps are found and upper bounds on the number of points in the smallest complete caps inPG(d,q) are tabulated for small parameters.This research was supported by the Academy of Finland.