Effect of homologous series of alkyl sulfate surfactants on the emulsion polymerization of styrene. I. Equal total concentrations

There is evidence in the literature that the rates of emulsion polymerization increase by a large factor as the alkyl chain length increases for a homologous series of surfactants. However, the area occupied by a surfactant molecule in a saturated monolayer at the polystryene/water interface is independent of chain length for alkyl sulfates so that, on the basis of Gardon's theory, equal rates of polymerization would be expected when equal concentrations of surfactants are used. There is a large increase in the number of polymer latex particles formed and in the rate of emulsion polymerization as the surfactant concentration is increased through the critical micelle concentration; this accounts for the large increases reported, because the lower members of the homologous series are below their critical micelle concentrations in most of the published studies. When a common concentration is chosen that is above the critical micelle concentration even for the lowest member of the series, only a relatively small increase in latex particle number and rate of emulsion polymerization with alkyl chain length of the surfactant is observed. This is attributable to an increase in the concentration of surfactant micelles. Good agreement with Gardon's theory is obtained when the concentration of micellar surfactant is used instead of the total surfactant concentration.     

Microstructure determination of poly-(1,3-pentadiene) by a combination of infrared, 60-MHz NMR, 300-MHz NMR,and X-ray diffraction spectroscopy

A quantitative procedure has been developed for characterizing the complete microstructure of polymers of 1,3-pentadiene, including the tacticity of any crystalline component. This can be accomplished by a combination of infrared spectroscopy, X-ray crystallinity, and 300-MHz NMR spectroscopy. A series of high structural purity polymers were synthesized with a series of previously unreported mixed microstructures. These samples were characterized by using the three techniques mentioned, including the previously unreported 300-MHz NMR data. With those results a 60-MHz NMR/IR method of spectroscopy was developed to determine the composition of poly(1,3-pentadiene)s in terms of percent cis-1,2-, cis-1,4-, trans-1,4-, and 3,4-pentadiene units.     

Die Anwendung des Derivatographen zur Gleichzeitigen Dilatometrischen und Differential-Thermischen Analyse von Gläsern

Simultaneous DTA and dilatometric measurements were made and the derivatives of the dilatometric curves were taken for three glasses by means of a derivatograph. Glass blocks were used as test pieces with a boring for the thermoelement. A maximum was observed in the rate of length change, which can be explained by overheating phenomena. A comparison with DTA curves of glass powders published by Yamamoto showed that the break points in the DTA curves of glass blocks do not coincide with the Tg points, but under identical conditions they can serve for the rapid characterization of the transformation range.     

An NQR study of the effects on the torsional oscillations of a molecular crystal due to uniaxial pressures

This work reports the experimental results of the uniaxial pressure dependence at various temperatures of the spin-lattice relaxation time, T₁, in paradichlorobenzene single crystals.The directionality of the pressure dependence, together the temperature dependence ot T₁ near room temperature, give us some information about the dependence of the molecular torsional frequencies and lifetimes of the oscillations ground levels with the intermolecular crystalline potential.     

Separation and identification of organic and organometallic compounds by use of a liquid chromatography-particle beam-glow discharge mass spectrometry combination

Evaluation of the particle beam glow discharge mass spectrometry (PB-GDMS) system as a detector for liquid chromatography (LC) is described for the analysis of polycyclic aromatic hydrocarbons, steroids, selenoamino acids, and alkyllead compounds. A particle beam interface is used to introduce analyte species from the LC into a glow discharge source for subsequent vaporization and ionization. Mass spectra display classic EI fragmentation patterns for the organic compounds, as well as elemental and molecular information for the organometallic compounds. Chromatographic separations display good temporal correlation between UV and PB-GDMS detection modes. Detection limits for Pb in lead nitrate, triethyllead, and triphenyllead fall in the sub-ppb (ng) range.     

Transuranic elements alpha-particle energy analysis using nuclear track in solids methodology

This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material, one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters. The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by²³⁹Pu,²⁴¹Am and²⁴⁴Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track diameter.     

Bivalent 3d-metal complexes of malonyl- and succinyldihydrazide based macrocyclic ligands. Synthesis and characterization

Summary The macrocycles 2,10-dimethyl-3,4,8,9,15-pentaazabicyclo-[9.3.1]-pentadeca-1 (15),2,9,11,13-penta-ene-5,7-dione (L) and 2,11-dimethyl-3,4,8,9,10,16-pentaazabicyclo[10.3.1]-hexadeca-1 (16),2,10,12,14-penta-ene-5,8-dione (L) were prepared and characterized by elemental, i.r. and mass spectral data. The macrocycles react with various metal(II) chlorides to yield complexes of the types [MLCl₂H₂O] (M = Mn, Co, Ni, Cu or Zn), [MLCl₂H₂O] (M = Mn, Ni, Cu or Zn) and [Co₃L₂Cl₄]Cl₂. The complexes were characterized by physico-chemical and spectroscopic methods.     

The role of surface oxides in formic acid oxidation on Au

Compared to Pt or Pd electrodes, Au is a poor catalyst for the direct anodic oxidation of HCOOH, but the formation of Au surface oxides in acidic solutions is accompanied by a fast oxidation of HCOOH. This fast reaction is not simply a secondary reaction of Au surface oxides since those oxides are kinetically stable in HCOOH solutions. They do oxidize HCOOH only via a slow and purely electrochemical process which occurs on free Au sites and is “driven” by oxide reduction. The fast HCOOH oxidation is due to a highly reactive intermediate which is able either to form stable Au oxides Au_nO_m or to react with HCOOH. Our results are consistent with the model that by the charge transfer step a reactive non-equilibrium {Au…O> species is formed which converts to stable equilibrium oxides Au_nO_m after migration and rearrangement steps. Pre-equilibrium <Au…O> oxidizes HCOOH and this oxidation is of lower order with respect to <Au…O> compared with the formation of Au_nO_m.     

Reactions of methyltris(triarylphosphine)cobalt : I. Formation of biaryls

Methyltris(triarylphosphine)cobalt (Ar₃P)₃CoCH₃, decomposes in solutions of THF, benzene or chlorobenzene to yield biaryls. Coupling to biaryls occurs at the ring carbon originally bonded to phosphorus. Mixed biaryls are obtained from crossover reactions of complexes bearing different triarylphosphine ligands and reactions of complexes with free triarylphosphines.     

Production of electronically excited NF by the reaction of fluorine atoms with HN3

Electronically excited NF in both the a¹Δ and b ¹Σ⁺ states hasbeen observed from the reaction of fluorine atoms with HN₃. The results suggest that fluorine atoms first abstract the hydrogen atom from HN₃, then react with the remaining N₃ to form NF^≠(a¹Δ). NF^*(b¹Σ⁺) is produced by a subsequent energy pooling reaction between NF^≠(a¹Δ) and vibrationally excited HF. The rate of the F + N₃ reaction is estimated to be ≈ 10¹² and ³ mole^?1 s^?1.