Crystal structure and spectroscopy of a most unusual Cu(II) coordination compound containing an infinite chain of lattice ligand interwoven with stacked sheets of neutral bis(2-aminopyrimidine-bridged) copper ions: X-ray structure of [Cu(ampym)2(H2O)2(CF3SO3)2](ampym)2(ampym)2

Reaction of Cu(II) triflate with an excess of 2-aminopyrimidine (ampym) in ethanol followed by slow crystallization results in a most unusual crystal lattice, which can be considered as consisting of two interpenetrating sublattices. The compound analyzes as [Cu(ampym)₂(H₂O)₂(CF₃SO₃)₂(ampym)₄]. Crystal data: Triclinic, P [`1]\overline 1 , a = 7.6179(5), b = 11.4311(14), c = 11.8373(13) Å, = 84.098(9), = 79.998(7), = 84.253(8)°, Vol = 1010.151(8) Å, Z = 1, D_calc = 1.592 g/cm³. One part of the lattice consists of the unprecendented linear chain of neutral ampym molecules; the chain is built up by Watson–Crick type bis-hydrogen bonds between imine N atoms and N-H groups of the NH₂. This ampym chain is apparently stabilized by the other part in the crystal lattice, which can best be described by starting from the centrosymmetric trans-Cu^II(ampym)₂(H₂O)₂ ion (Cu-N = 2.01 Å; Cu-O = 1.94 Å). This Cu ion is coordinated by two monodentate ampym ligands, two water molecules and two semi-coordinating triflate oxygen atoms. The Cu chromophore is held in position by hydrogen bonding towards a triflate ion (two times for symmetry reasons), and (again two times) a free ampym ligand. The triflate ion bridges a water hydrogen to a next-neighboring free ampym ligand. The noncoordinating ampym molecule has four bonding sites, of which two are used in H-bonding with the coordinated ligand, one with the triflate and the last one with the water hydrogen atom. The noncoordination ampym molecules in this sublattice finally form aromatic stacks with coordinated ampym and with itself in pairs (ring-ring distance 3.77-3.80 Å).     

Effect of catalyst partitioning in Co(II) mediated catalytic chain transfer miniemulsion polymerization of methyl methacrylate

The effect of catalyst partitioning over the organic and water phases in the catalytic chain transfer mediated miniemulsion polymerization was investigated and a mathematical model developed to describe the instantaneous degree of polymerization of the formed polymer. Experimental and predicted instantaneous degrees of polymerization prove to be in excellent agreement. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5839–5849, 2008     

Graft modification of starch nanoparticles with pH-responsive polymers via nitroxide-mediated polymerization

The grafting to approach and nitroxide-mediated polymerization (NMP) were used to graft modify starch nanoparticles (SNP) with pH-responsive polymers. SG1-capped poly(2-(dimethylamino)ethyl methacrylate-co-styrene), P(DMAEMA-co-S), and poly(2-(diethylamino)ethyl methacrylate-co-styrene), P(DEAEMA-co-S), with relatively low dispersity and high degree of livingness was synthesized in bulk via NMP using a commercial available alkoxyamine. These macroalkoxyamines were then grafted to vinyl benzyl-functionalized SNP (SNP-VBC) to obtain pH-responsive materials. The grafted SNP were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis confirming the successful synthesis of these new materials. Low grafting efficiencies (~6%) were observed for both SNP-grafted materials with pH-responsive polymers, as expected when using the grafting to approach. The pH-responsiveness of SNP-g-P(DMAEMA-co-S) and SNP-g-P(DEAEMA-co-S) was confirmed by measuring the ζ-potential at different pH values. At acidic conditions (pH 3–6) the grafted materials were protonated and exhibited positive ζ-potential, whereas at basic conditions (pH 10–13) the same grafted materials were deprotonated and exhibited negative ζ-potential.     

On the number of polynomials over GF(2) that factor into 2, 3 or 4 prime polynomials

In this paper a simple method is presented to derive formulas for the number of polynomials over GF(2) which factor into two, three, and four prime polynomials only. A table is given, summarizing the above numbers for polynomials of degree up to 127. Furthermore, the computed values are compared with an asymptotic approximation for these values.This work was supported in part by the National Swedish Board for Technical Development under grants 81-3323 and 83-4364 at the University of Lund.     

An experimental investigation on high-frequency vacuum arcinterruption at small gap length

An experimental study of high-frequency (126, 230 kHz) vacuum arc interruption behavior and the voltage escalation processes at a small gap length (⩽1 mm) for three contact materials (Cu, CuCr, and CuTeSe) is discussed. Two experimental methods have been used: current injection in a low-voltage circuit and in a 10-kV AC circuit. Experimental results of the high-frequency current interruption ability and the dielectric breakdown voltage are presented. Three kinds of breakdown are distinguished: the reignition voltage, the breakdown voltage, and the cold breakdown voltage. It has been found that the interruption ability is directly related to the reignition voltage     

High‐Silica Zeolite SSZ‐61 with Dumbbell‐Shaped Extra‐Large‐Pore Channels

The synthesis of the high‐silica zeolite SSZ‐61 using a particularly bulky polycyclic structure‐directing agent and the subsequent elucidation of its unusual framework structure with extra‐large dumbbell‐shaped pore openings are described. By using information derived from a variety of X‐ray powder diffraction and electron microscopy techniques, the complex framework structure, with 20 Si atoms in the asymmetric unit, could be determined and the full structure refined. The Si atoms at the waist of the dumbbell are only three‐connected and are bonded to terminal O atoms pointing into the channel. Unlike the six previously reported extra‐large‐pore zeolites, SSZ‐61 contains no heteroatoms in the framework and can be calcined easily. This, coupled with the possibility of inserting a catalytically active center in the channel between the terminal O atoms in place of H⁺, afford SSZ‐61 intriguing potential for catalytic applications.