Influence of organic modifiers on morphology and crystallization of poly(ϵ‐caprolactone)/synthetic clay intercalated nanocomposites

ε‐caprolactone was polymerized in the presence of neat montmorillonite or organomontmorillonites to obtain a variety of poly(ε‐caprolactone) (PCL)‐based systems loaded with 10 wt % of the silicates. The materials were thoroughly investigated by different X‐ray scattering techniques to determine factors affecting structure of the systems. For one of the nanocomposites it was found that varying the temperature in the range corresponding to crystallization of PCL causes reversible changes in the interlayer distance of the organoclay. Extensive experimental and literature studies on this phenomenon provided clues indicating that this effect might be a result of two‐dimensional ordering of PCL chains inside the galleries of the silicate. Small angle X‐ray scattering and wide angle X‐ray scattering investigation of filaments oriented above melting point of PCL revealed that polymer lamellae were oriented perpendicularly to particles of unmodified silicate, while in PCL/organoclay systems they were found parallel to clay tactoids. Calorimetric and microscopic studies shown that clay particles are effective nucleating agents. In the nanocomposites, PCL crystallized 20‐fold faster than in the neat polymer. The crystallization rate in nanocomposites was also significantly higher than in microcomposite. Further research provided an insight how the presence of the filler affects crystalline fraction and spherulitic structure of the polymer matrix in the investigated systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2350–2367, 2007     

TEM investigations on PECVD-titanium carbide layers

TiC_x-PECVD-layers were characterized by TEM. EDX analysis and electron diffraction. TiC_x-layers deposited using benzene showed a columnar structure, at which the column size decreases with rising excess carbon content. TiC_x-layers deposited using n-heptane presented a lamellar structure, at which the lamellar thickness diminishes with an increasing excess carbon content. In dependence on the layer thickness a periodic progress of the element contents was observed, at which a maximum for Ti and Cl correlates with a minimum for C. It was found that the incorporated chlorine is bonded to titanium. The lattice parameter depends on the chlorine content. Using TiCl₄/H₂/Ar-gas mixtures without any hydrocarbon, layers containing TiH₂ are formed.     

Über zwei Gitterpunktprobleme

Ohne Zusammenfassung ^k (s) = ((s)) ^k , und ebenso in allen analogen Fällen.     

Theory of mixed-polarization propagation in anisotropic cubic media

Polarization dynamics are considered in the presence of an anisotropic Kerr non-linearity in the most common semiconductor waveguide geometry. The equations of motion are formulated in terms of Stokes polarization parameters and their Hamiltonian form is derived. Stationary solutions and their stability are found for plane-wave propagation. It is found that the non-integrable problem of mixed-polarization spatial soliton dynamics can be largely explained in terms of the equivalent plane-wave solutions.     

Synthesis and capsule formation of upper rim substituted tetra-acrylamido calix[4]arenes

Upper rim substituted tetraiodo calix[4]arenes are coupled to a variety of acrylamides using the palladium catalysed Heck reaction. Tetra-acrylamido upper rim substituted calix[4]arenes are obtained in good yields with exceptionally high stereoselectivity, to produce the all-trans isomers. Tetra-acrylamido calix[4]arenes derived from secondary acrylamides are shown to dimerise via eight hydrogen bonds to form dimeric capsules, which are able to include small organic molecules.     

Nitropyrazoles

The double Vilsmeier formylation of theC-methyl group in pyrazole derivatives has been shown to occur when a nitro-group is in the adjacent position of the ring. A method for the synthesis ofC-(diformylmethyl)nitropyrazoles based on this reaction has been developed.For the previous communication, see Ref. 1; for Part 2, see Ref.2 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1273–1276, July, 1993.     

Determination of uranium after its selective extraction as phenylacetate

The method described is based on the extraction of uranium with a chloroform solution of phenylacetic acid from slightly acidic solution containing nitrilotriacetic acid, which masks all interfering metals. After stripping into very dilute hydrochloric acid, uranium is reduced with ascorbic acid and determined complexometrically. The method permits reliable determination of uranium in the presence of all quadri-, ter- and bivalent metals investigated, molybdenum(VI), tungsten(VI), and vanadium(V).