Living cationic polymerization of vinyl ethers by electrophile/lewis acid initiating systems. XII. Phosphoric and phosphinic acids/zinc chloride initiating systems for isobutyl vinyl ether

Phosphoric and phosphinic acid derivatives (R¹R²PO₂H; R¹, R² = OPh, OPh; OnBu, OnBu; Ph, Ph; Ph, H) in conjunction with zinc chloride (ZnCl₂) led to living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene below 0°C. The number-average molecular weights (M?_n) of the polymers (M?_n > 2 × 10⁴) were directly proportional to monomer conversion and in excellent agreement with the calculated values assuming that one polymer chain forms per R¹R²PO₂H molecule. Throughout the reaction, the molecular weight distributions (MWDs) stayed narrow (M?_w/M?_n ? 1.1). A dibasic acid, PhOP (O) (OH)₂, coupled with ZnCl₂, also induced living cationic polymerization of IBVE where one molecule of the acid generated two living polymer chains. The polymerization by (PhO)₂PO₂H/ZnCl₂ and its model reactions were directly analyzed by ³¹P and ¹H-NMR spectroscopy. The analysis showed that the acid initially forms the adduct [CH₃CH(OiBu)OP(O)(OPh)₂], the phosphate linkage of which is in turn activated by ZnCl₂ so as to initiate living propagation. The finding thus indicates that (PhO)₂PO₂H indeed acts as an initiator in the living polymerization. The NMR analysis also suggested that an exchange reaction occurs between the phosphate group at the polymer terminal and the chlorine in ZnCl₂. The occurrence of living IBVE polymerization with these various R¹R²PO₂H/ZnCl₂ systems shows that phosphoric and phosphinic acids are another general class of protonic acids which are effective initiators for the living cationic polymerization assisted by Lewis acids. © 1993 John Wiley & Sons, Inc.     

Investigation of luminescence and photoelectrochemical properties of rare-earth metal-doped anode oxide films on aluminum

A study is made of the luminescence of rare-earth-metal (REM)-doped anode oxide films (AOF) grown on aluminu. It is shown that REMs introduced into an AOF in the course of its formation exert a considerable influence on the position of the maximum half-width and the intensity of the luminescence spectrum of the matrix, i.e., Al₂O₃. Photoelectrochemical properties of AOF (Eu) are investigated. A dependence of the AOF photopotential on the conditions of its formation is shown. Belarusian State University of Information Science and Radioelectronics, 6, P. Brovka St., Minsk, 220600, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 593–596, July–August, 1998.     

Theoretical Study on the Kinetics of Electron Transfer for Bond—breaking Reaction

ＩｎｔｒｏｄｕｃｔｉｏｎＦｒｅｅｒａｄｉｃａｌｆｏｒｍａｔｉｏｎｆｒｏｍｈａｌｏｇｅｎａｔｅｄｈｙｄｒｏｃａｒｂｏｎｓｈａｓｒｅｃｅｉｖｅｄｃｏｎｓｉｄｅｒａｂｌｅａｔｔｅｎｔｉｏｎｂｅｃａｕｓｅｏｆｉｔｓｓｃｉｅｎｔｉｆ ｉｃａｎｄｅｎｖｉｒｏｎｍｅｎｔａｌｒｅｌｅｖａｎｃｅ .1 6 Ｔｈｉｓｒｅａｃｔｉｏｎｓｅｅｍｓｔｏｐｌａｙａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｖａｒｉｏｕｓｐｒｏｃｅｓｓｅｓ .Ｂｏｎｄ ｂｒｅａｋ ｉｎｇｒｅａｃｔｉｏｎｉｓａｐｏｗｅｒｆｕｌｓｙｎｔｈｅｔｉｃｔｏｏｌｔｏｐｒｏｖ…     

Synthesis and Crystal Structur of (4,4′-H_2bipy)[CdBr_4]·H_2O

The title compound (4,4′-H2bipy)[CdBr4]·H2O 1 has been synthesized via hydrothermal reaction and characterized by X-ray diffraction. The crystal belongs to monoclinic,space group P21/c with a=8.260(3),b=23.926(7),c=9.774(2),β=106.777(9)o,C10H12Br4CdN2O,Mr=608.26,V=1849.4(9)3,Z=4,Dc=2.185 g/cm3,S=1.005,μ(MoKα) =9.814 mm–1,F(000)=1128,R=0.0646 and wR=0.0989. The crystal structure analysis of 1 reveals that the title compound features an isolated structure,based on discrete 4,4′-H2bipy moieties and lattice water molecules which are linked by hydrogen bonds together with tetra-hedral cadmium atoms terminally coordinated by four bromine atoms.     

Luminescent properties of AIIB2IIIC4VI compounds

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 3, pp. 145–151, May–June, 1995.     

Scattering loss in Nd-doped silica based optical fibers

Rare-earth doped fibers suffer from relatively high attenuation in comparison to conventional communication fibers. In order to improve the properties of such fibers, understanding of the mechanisms involved in scattering effects is of great importance. The effect of Nd-doping, Al-codoping and of the drawing temperature on the scattering effect was investigated for several different optical fibers. To this end a measuring setup was realized which allows absolute measurements of the scattering coefficient at different positions along a fiber. Also separation of total attenuation and scattering effects is possible. The presented results indicate scattering effects as primary source for increased attenuation compared with undoped fibers.     

Die Kristallstrukturen der Monohydrate von Lithiumchlorid und Lithiumbromid

Crystal Structure of the Monohydrates of Lithium Chloride and Lithium Bromide Using single crystal analysis and powder diffraction data the crystal structures of the monohydrates of lithium chloride and lithium bromide were solved. Both compounds crystallise isotypic in the space group Cmcm (LiCl·H₂O: single crystal analysis; T = 100 K; a = 758, 35(2); b = 768, 07(2); c = 762, 35(2) pm; Z = 8; 1179 unique reflections; R₁ = 0, 0196. LiBr·H₂O: Rietveld‐refinement; T = 220 K; a = 806, 15(1); b = 799, 44(1) und c = 794, 61(1) pm; Z = 8; 157 unique reflections; R_p = 0, 0922; R_wp = 0, 0979; R_exp = 0, 0657). The structure derives from the perowskite structure according to the formula X(H₂O)Li□₂ (X = Cl, Br). The orientation of the water molecules is linked clearly to the distribution of the lithium cations and vice versa. The high level ionic conductivity in the cubic high temperature phase of LiBr·H₂O is related to the initial rotation of the water molecules during the phase transformation. This motion favours the lithium ion hopping and the melting of the lithium substructure respectively.     

Electron diffraction data as a constraint in the determination of force field of thallous halide dimers

Electron diffraction data have been used as a constraint in the determination of force field for Tl₂F₂ having planar rhombic structure. The L-F approximation method, recently given by us, has also been applied to evaluate force constants for thallous halide dimers,e.g. T1₂F₂ and T1₂Cl₂. The results have been compared with the available experimental data in order to check the validity of the present work. It is concluded that non-bond experimental mean amplitudeU ₁..._Tl for Tl₂F₂ is capable of fixing the force field and L-F approximation gives reasonably good force fields for the two thallous halide dimers now under study.     

Organic halide-alcohol interactions: Observation by means of the glass transition

The glass-transition temperature (T _g) in binary mixtures of the primary alkanols with CBr ₄ and CHBr ₃ has been measured as a function of composition. The results are compared with earlier studies on alkanol solutions of organic chlorides. The initial molar slope (IMS) of theT _g vs. composition curve at the pure alkanol indicates formation of a 1:1 halide-alkanol complex stabilized by a specific halogen-oxygen interaction. The IMS values decrease in the order CBr ₄ >CHBr ₃ >CCl ₄ >CHCl ₃ >CH ₂ Cl ₂ , reflecting decreasing stability of the complex.     

Optical transitions of Eu3+ ions in EuCl3 solutions

The optical absorption spectra of EuCl₃ in aqueous and acidic solutions were measured in the visible anduv regions of the spectrum. The concentration as well as the temperature of the solutions were varied to establish an accurate free-ion energy level scheme of Eu³⁺. The energy levels were assigned on the basis of a correlation between the calculated and the experimentally observed transition energies and associated band intensities.