Bionanocomposites poly(ϵ-caprolactone)/organomodified Moroccan beidellite clay prepared by in situ ring opening polymerization: Characterizations and properties

In this study, a series of poly(?-caprolactone) (PCL)/clay bionanocomposites were prepared via in situ ring opening polymerization (ROP) of ?-caprolactone catalyzed by titanium butoxide. The natural Moroccan clay beidellite (BDT), used as nanocharge, was organomodified with cetyltrimethylammonium bromide, CTA, to obtain the organically modified 3CTA-BDT (3 = CTA/BDT equivalent feed ratio). Characteristics of the final nanocomposites are investigated by FTIR, SEC, XRD, SEM, TGA, DSC, optical tensiometry, thermal conductivity and water vapor sorption analysis. The intercalated/exfoliated morphologies, revealed by XRD and SEM analyses, confirm uniform dispersion of the nanoclay within the PCL matrix. Thermal stability of all the nanocomposites is improved by the addition of 3CTA-BDT clay compared to pure PCL polymer. The DSC data show that the addition of 3CTA-BDT particles promotes an increase in the disorder of the crystalline phase, which reduces the crystallinity degree. The hydrophobicity of Polymer/clay compatibility was analyzed by studying surface polarity degree of samples by contact angle measurements. Thermal conductivity and water vapor sorption was also discussed. The permeability (P), the sorption coefficient (S) and the diffusion coefficient (D), showed a significant decrease with increasing 3CTA-BDT loading.     

Ferrocene based chiral binuclear η6‐benzene‐Ru(II)‐phosphinite complexes: Synthesis,characterization and catalytic activity in asymmetric reduction of ketones

In the present study, a series of chiral C₂‐symmetric ferrocenyl based binuclear η⁶‐benzene‐Ru(II) complexes bearing diphenylphosphinite and diisopropylphosphinite moieties have been synthesised. The new binuclear η⁶‐benzene‐Ru(II)‐phosphinite complexes were characterised based on nuclear magnetic resonance (¹H, ¹³C, ³¹P–NMR), FT‐IR spectroscopy and elemental analysis. Then, these complexes have been screened as catalytic precursors in the transfer hydrogenation of acetophenone with 2‐propanol as both the hydrogen source and solvent in the presence of KOH. The corresponding optically active secondary alcohols were obtained in excellent conversion rates between 96 and 99% and moderate to good enantioselectivities (up to 78% ee). The complex 5 was the most efficient catalyst among the four new complexes investigated herein.     

On the mechanical and thermomechanical properties of low-density polyethylene/ethylene-α-octene copolymer blends

Blends of low-density polyethylene (LDPE) and ethylene-octene copolymer (EOC) were obtained. The effect of EOC content and absorbed radiation dose on the mechanical and thermomechanical properties of LDPE/EOC blends are investigated. Particular attention is given to a tensile stress-strain analysis and the “form-memory” effect of the blends. With growing LDPE content, the elastic modulus, the yield stress, and the thermorelaxation and residual stresses of the blends increase, but the ultimate elongation at break decreases, which is caused by the higher crystallinity of polyethylene. As a result of radiation-induced cross-linking, the elastic modulus, the yield stress (at a 1% strain), the ultimate yield strength, and the thermorelaxation and residual stresses increase, while the ultimate elongation at break and the melt flow-behavior index decrease, which is confirmed by the growing gel fraction in the blend. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 279–286, March–April, 2008.     

Catalytic effect of sodium chloride on limestone calcination and sulphation — electron microscopy and eds studies

Thermogravimetric studies on the influence of sodium chloride on the kinetics of limestone sulphation were supported by scanning electron microscopy and energy dispersive X-ray microanalysis.On the basis of morphological observations on calcined and sulphated limestone and elemental microanalysis in an electron microprobe it was found that NaCl affects the sintering, favouring the formation of more compact structures of rounded crystallites during sulphation. Chlorine is largely lost during sulphation. Capacity of the sorbents under both TG and FBC conditions depends strongly on when and how the NaCl is introduced.

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Zusammenfassung In Verbindung mit Scanning Elektronenmikroskopie und Röntgenmikroanalyse wurden thermogravimetrische Untersuchungen des Einflusses von Natriumchlorid auf die Kinetik der Sulfierung von Kalkstein durchgeführt.Auf der Grundlage von morphologischen Beobachtungen an kalziniertem und sulfiertem Kalkstein und durch Elementarmikroanalyse in einem Elektronenstrahlmikroanalysator wurde festgestellt, daß NaCl das Sintern beeinflußt. Infolgedessen wird bei der Sulfierung die Entstehung von abgerundeten Kristalliten begünstigt. Chlor wird während der Sulfierung größtenteils abgegeben. Die Kapazität der Sorptionsmittel hängt sowohl bei TG als auch bei FBC stark davon ab, wann und wie das NaCl eingebracht wurde.

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The authors wistl to thank Prof. E. M. Bulewicz of the Technical University of Cracow for helpful discussions and Mr. S. Sivonen of the University of Oulu for making available the facilities the SEM and EDS-X-ray microanalysis at the Institute of Electron Optics.     

An efficient approach to d-threo-3-hydroxyaspartic acid for the synthesis of novel l-threo-oxazolines as selective blockers of glutamate reversed uptake

An efficient, stereoselective synthetic strategy to d-threo-3-hydroxyaspartic acid was developed. Starting from l-(2S,3S)-N-benzoyl-3-hydroxyaspartic acid dimethyl ester by a Deoxo-fluor-catalyzed cyclization reaction, an inversion of configuration at the β-center (erythro isomer), was observed. A base-induced epimerization reaction led to the d-trans-isomer, which was hydrolyzed to give d-threo-3-hydroxyaspartic acid with excellent stereoselectivity and overall yield. Starting from d-threo-3-hydroxyaspartic acid, l-threo-oxazolines can be stereoselectively synthesized.     

Direct photochemical patterning and refunctionalization of supported phospholipid bilayers

A wet photolithographic route for micropatterning fluid phospholipid bilayers is demonstrated in which spatially directed illumination by short-wavelength ultraviolet radiation results in highly localized photochemical degradation of the exposed lipids. Using this method, we can directly engineer patterns of hydrophilic voids within a fluid membrane as well as isolated membrane corrals over large substrate areas. We show that the lipid-free regions can be refilled by the same or other lipids and lipid mixtures which establish contiguity with the existing membrane, thereby providing a synthetic means for manipulating membrane compositions, engineering metastable membrane microdomains, probing 2D lipid-lipid mixing, and designing membrane-embedded arrays of soluble proteins. Following this route, new constructs can be envisaged for high-throughput membrane proteomic, biosensor array, and spatially directed, aqueous-phase material synthesis.