Materials Literature
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The melting behavior of poly(butylene terephthalate) crystallized isothermally for various times was examined using differential scanning calorimetry. After short crystallization times, the DSC analysis gave two melting peaks, but after longer times, the analysis gave three peaks. The latter triplet of DSC peaks can b…
Linearly polarized (LP) UV photoreaction of a photo-crosslinkable side-chain liquid-crystalline polymer (SLCP) containing photoreactive cinnamoyl and biphenyl mesogenic groups (1) was studied. The optical anisotropy of the polymer film was induced by the LP-UV photoreaction and was investigated by the temperature-cont…
Functionalized cyclopentadithiophenes 2 and 3 were synthesized and polymerized by anodic coupling, in acetonitrile solution, in the presence of 0.1 M tetraethylammonium perchlorate as supporting electrolyte. The former carries a 16-crown-5-ether ring coplanar to the bithiophene moiety, while a perpendicular 15-crown-5…
Poly(styrene-co-maleic anhydride)/silica hybrid material has been successfully prepared from styrene–maleic anhydride copolymer and tetraethoxysilane (TEOS) in the presence of a coupling agent (3-aminopropyl)triethoxysilane (APTES) by an in situ sol–gel process. It was observed that the gel time of sol–gel solution wa…
A main chain hydrogen-bonded liquid crystalline polymer was formed by melt mixing two complementary components, A and B, which in their individual states do not exhibit liquid crystallinity. The structure of the polymer and the thermal stability of its mesophase were studied using synchrotron radiation SAXS/WAXS/DSC a…
With the aim of studying next-neighbor magnetic interactions in polymeric metallocenes the paramagnetic decamethylbimetallocenes (M'M') have been chosen as most simple model compounds. They have been synthesized for vanadium, cobalt, and nickel (to yield V'V', Co'Co', and Ni'Ni', respectively) by starting from dilithi…
Four new &mgr;-CO(3)(2-) copper(II) complexes with different coordination modes for the carbonato bridge have been obtained by fixation of atmospheric CO(2): {(&mgr;(3)-CO(3))[Cu(3)(ClO(4))(3)(Et(3)dien)(3)]}(ClO(4)) (1), Et(3)dien = N,N',N"-triethylbis(2-aminoethane)amine; {(&mgr;-CO(3))[Cu(2)(H(2)O)(Et(4)dien)(2)]}(…
The influence of different types of low and atmospheric pressure plasma on poly(ethylene terephthalate) (PET) has been studied in terms of changes in molar mass and molar mass distribution. Apart from a variation of plasma gases (oxygen, helium) different types of plasma (microwave, radio frequency, corona discharge)…
Tetraheptylammonium salts of various transition-metal-substituted heteropolyanions with alpha-Keggin ([XW(11)O(39)M](n)()(-)), alpha-Wells-Dawson ([P(2)W(17)O(61)M](m)(-)), and Weakley and Finke structures ([P(2)W(18)O(68)Co(4)](10)(-)) were investigated with respect to their reactivity with CO(2) in nonpolar solvents…
The precipitation polymerization of commercial divinylbenzene in acetonitrile containing up to 40 vol. % toluene or other cosolvents is shown to produce novel porous monodisperse poly(divinylbenzene) microspheres. These microspheres have diameters between 4 and 7 μm, total pore volumes of up to 0.52 cm3/g, and surface…
We advance the novel hypothesis that water in the presence of finite localized strain within fault gouges may lead to the phase transformation of stable minerals into metastable polymorphs of higher free energy density. Under increasing strain, the transformed minerals eventually become unstable, as shown from an appl…
If the amylose fraction of starch is degraded by glucosyltransferases, one or several turns of the amylose helix are hydrolyzed off and their ends are joined together, thereby producing cyclic oligosaccharides called cyclodextrins (CDs) or cycloamyloses (CAs).
Conditions are described under which the nonphysiological substrate mercuric bromide (HgBr2) is rapidly turned over, both by the wild type (CCCC) and by an active site double mutant (CCAA) of mercuric reductase in which the C-terminal cysteines 557' and 558' are replaced by alanine and only the redox-active pair Cys13…
A disordered loop (loop 52-72, residues 52-72) in crystal structures of fructose-1,6-bisphosphatase (FBPase) has been implicated in regulatory and catalytic phenomena by studies in directed mutation. A crystal structure of FBPase in a complex with three zinc cations and the products fructose 6-phosphate (F6P) and phos…
Ultraviolet irradiation of formamide in solid argon forms hydrogen-bonded, carbon- and oxygen-attached complexes NH 3 −CO and NH 3 −OC. Computationally, the carbon-attached complex is 1.2 kJ mol -1 more stable than the oxygen-attached complex. However, a thermal equilibrium of the two structures is found experimentall…
UDP-galactose 4-epimerase catalyzes the interconversion of UDP-galactose and UDP-glucose during normal galactose metabolism. Within recent years the enzyme from Escherichia coli has been studied extensively by both biochemical and X-ray crystallographic techniques. One of several key features in the catalytic mechanis…
In a previous contribution ( J. Phys. Chem. 1994, 98, 4125) we reported EXAFS data collected at ADONE on a high quality Ti−silicalite (TS-1) sample (Ti = 1.47 wt %) dehydrated in a carefully controlled atmosphere at 400 K. The importance of that paper was to definitively clarify that Titanium atoms occupy silicon subs…
The seeded and unseeded precipitation of calcium carbonate from supersaturated aqueous solutions was investigated in a closed system under conditions of constant supersaturation (supersaturation 1.88−3.39) at 25 °C and at pH 9.0 and 10.0. The analysis of our results based on expressions for the supersaturation depende…
Solubilities of four heavy n -alkanes (tricosane, pentacosane, hexacosane, and octacosane) in a solvent containing seven atoms of carbon (heptane, methylcyclohexane, and toluene) are determined by simple thermal analysis. It is shown that the nature of the solvent has no major influence on the solubility and that, in…
2-Oxo-hept-4-ene-1,7-dioate hydratase from Escherichia coli C converts 2-oxo-hept-4-ene-1,7-dioate to 2-oxo-4-hydroxy-hepta-1,7-dioate by the addition of water using magnesium as a cofactor. The enzyme is one of a set of inducible enzymes, known collectively as the homoprotocatechuate meta-fission pathway. The entire…