Improved synthesis of oligomeric phthalonitriles and studies designed for low temperature cure

An improved synthetic method has been developed for oligomeric aromatic ether ketone‐based phthalonitrile (PN) resins. A new curing additive was studied that lowers the cure temperature of the PN resin to around 150 °C and compared to the traditional high‐temperature aromatic diamine. Mechanical and thermo‐oxidative analyses of polymeric samples from both systems were determined and compared under various curing conditions. The PN polymer exhibited low water absorption regardless of the chosen cure system. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1662–1668     

Stabilization of the bis(diphenylphosphino) methanide ion by bridging dirhenium octacarbonyl: [Li(THF)4 ]IRe2(CO)8(Ph2PCHPPh2)]

The anion of [Li(THF)₄][Re₂(CO)₈(Ph₂PCHPPh₂)] (1) is formed cleanly by treatment of Re₂(CO)₈(Ph₂PCH₂PPh₂) with LiAlH₄ in tetrahydrofuran (54% yield). Anion 1 is remarkably stable toward all organic electrophiles examined. Whereas protons are added and removed reversibly, 1 is stable to treatment with MeI, Me₃SiCl, Me₃SiCH₂Cl or Ph₂PCl, even under forcing conditions. This behavior sharply contrasts the high reactivity of other mononuclear (Ph₂PCHPPh₂)ML_x complexes.     

Local duality constraints on scalar gluonium

We study O⁺⁺ (gg) channel in the framework of the Gauss-Weierstrass QCD sum rules. The results of this analysis definitely support the existence of a scalar gluonium bound state. Concerning the parameters of such a state, the case of a light and very narrow glueball turns out to be strongly favoured over that of a heavy and broad resonance.     

Determination of quark and gluon vacuum condensates from τ-lepton decay data

The values of the gluon and four-quark vacuum condensates are estimated using recent experimental data on the semileptonic τ-lepton decays τ→v_τ+nπ, which determine the vector and axialvector hadronic spectral functions. An optimal estimate is achieved through a systematic combined use Finite Energy, Laplace and Gaussian transform QCD sum rules. As a byproduct, the values of the dimensiond=8 vacuum condensates in the vector and axial-vector channels are also estimated.     

Uptake of hydrophobic amino acids and sodium chloride by a strong cation exchanger: Application to desalting and separation by preparative liquid chromatography

Summary The uptake of sodium chloride, leucine and phenylalanine by a strong cation-exchange resin in the sodium form have been compared. Sodium chloride was excluded from the resin, as indicated by its parabolic upwards curved isotherm, and the corresponding desorption edge was sharpened (constant pattern). Isotherms for both amino acids constructed from a single elution experiment displayed slightly downwards curvature; the corresponding desorption edges spread in contrast to the breakthrough ones. The affinities of both amino acids for the resin were higher (from 15 to 40 %) in the presence of 1 M sodium chloride, indicating that hydrophobic interactions played a significant role in the mechanism of sorption. As expected from the isotherms, a mixture of 1 M sodium chloride, leucine and phenylalanine was separated with satisfactory recovery of both amino acids for a column loading of 10 % of the bed volume. Real mother liquors have also been separated under the same conditions.     

Gelled emulsions with a high water content

The structure of a gel containing 99% water, 0.5% of a nonionic surfactant and 0.5% of a hydrocarbon was investigated by analysis of its equilibrium phases and their state of dispersion by liquid helium freeze fracture electron microscopy.The gel consisted of aqueous droplets of micron size separated by a thin membrane of a lamellar liquid crystal and a W/O microemulsion with droplets varying between 200 and 1000 Å in diameter.