Hydration characterization of N-vinylcaprolactam polymers by absorption millimeter-wave measurements

Water molecules in the polymer hydration shell known as bound water lose their mobility in comparison with unperturbed water. This effect was quantified by absorption measurements in the millimeter-wave range of microwaves (1–10 mm, 30–300 GHz). Hydration measurements were performed for poly(N-vinylcaprolactam) (PNVCL) and copolymers of N-vinylcaprolactam (NVCL) and N-vinylimidazol (NVIA). The association of hydrophobic groups in PNVCL upon coil-to-globule transition was found to cause a decrease in the relative hydration number, which is the relative amount of bound water per solute molecule as measured by microwave method at 31 GHz. Millimeter-wave hydration measurements were confirmed by the determinations of specific heat capacity (c _p) with differential scanning calorimetry. Hydration determinations of NVCL/NVIA copolymers revealed that they associate via hydrophobic clustering with a decrease in hydration of hydrophobic groups.     

Chromatographic and spectroscopic studies on the chiral recognition of sulfated β-cyclodextrin as chiral mobile phase additive: Enantiomeric separation of a chiral amine

A fast enantiomeric separation of a chiral aromatic amine was achieved, using ultra high pressure liquid chromatography and highly sulfated beta-cyclodextrin (S-β-CD) as a chiral additive in the mobile phase. The stationary phase consisted of a core–shell support with a particle size of 2.7 μm. Under these conditions the base-line separation was obtained within 2.5 min. The influence of the concentration of the additive, along with the thermodynamics of the separation, was studied. Vibrational circular dichroism (VCD) spectroscopy was applied to assess the absolute configuration of the two enantiomeric analytes, as well as the interaction of these enantiomers with the S-β-CD. The VCD results revealed that S-β-CD undergoes a temperature-induced conformational change. Further, VCD experiments indicate that the interactions of the two enantiomers with the S-β-CD occur through an inclusion of the aromatic part of the analyte, as well as through electrostatic interaction between the protonated amine and the sulfate groups located at the narrow part of the S-β-CD. Molecular mechanics calculations performed according to the VCD results are consistent with experimental data, providing further evidence of these interactions.     

Nanostructured catalysts for direct electrooxidation of dimethyl ether based on Bi- and trimetallic Pt–Ru and Pt–Ru–Pd alloys prepared from coordination compounds

Bi- and trimetallic platinum–ruthenium and platinum–ruthenium–palladium catalysts with specified atomic ratios Pt: Ru = 1: 1 and Pt: Ru: Pd = 1: 1: 0.1, respectively, were synthesized from the coordination compounds of the metals deposited on highly dispersed carbon black. The catalysts were characterized by powder X-ray diffraction, electron dispersive analysis, and transmission electron microscopy. According to voltammetry data, the highest activity in the dimethyl ether (DME) electrooxidation is exhibited by the catalyst Pt_0.43Ru_0.47Pd_0.1/C; hence, it may be considered as a promising anode material for direct DME fuel cells.     

Study of viscous liquids by spin micro- and macroprobe methods at 2-mm wave band EPR

The possibility of combined application of spin microprobe and macroprobe methods at 2-mm wave band EPR in determining the viscosity of a model system is demonstrated. Such an approach widens the range of dynamic viscosity EPR measurement in condensed systems and gives one the possibility to study separately various dynamic processes in a matrix.     

Viscoelastic properties of ϰ-carrageenan gels

Summary A study has been made of the creep behaviour of -carrageenan in the region of linear viscoelasticity in the temperature interval 9–50 °°C and concentration range 1.0–2.5%. It is shown that the rate of the elementary relaxation processes is independent of the concentration of -carrageenan. The following three temperature intervals where -carrageenan gels exist have been established: (1) the temperature interval corresponding to the stable helix conformation of the macromolecules; (2) the temperature interval of macromoleculer unwinding; (3) the high-temperature interval where the gel three-dimensional network is formed by the unwound macromolecules. The break-down enthalpy of the gel junction zones is 36, 234 and 36 KJ/mole, respectively.     

Electrochemical fluoroalkylation of ethylene

Conclusions The anodic trifluoromemylation of ethylene, vinylidene fluoride, and dimeoiyl maleate was effected, and the role played by the head to head doubling of the olefins in forming the dimeric products was shown.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2825–2827, December, 1977.     

Novel cationic amphiphilic derivatives from vernonia oil: synthesis and self-aggregation into bilayer vesicles, nanoparticles, and DNA complexants

Self-assembling nanostructures were prepared from novel cationic amphiphilic compounds synthesized from vernonia oil, a natural epoxydized triglyceride. The presence of a 12,13-epoxy group on the C18 unsaturated fatty acid, vernolic acid, which is the main constituent of vernonia oil, permitted the synthesis of novel amphiphilic derivatives with a hydrogen-bonding hydroxyl and a cationic headgroup moiety on adjacent carbon atoms. The amphiphiles were prepared in a two-stage synthesis that comprised opening of the epoxy groups with a haloacetic acid, followed by quaternization of the halo group with a tertiary amine containing a C12 aliphatic chain. Intact vernonia oil as the starting material gave a triple-headed cationic amphiphile, containing three vernolic acid derived moieties connected through a glycerol backbone. A single-headed amphiphile with two alkyl chains and a single quaternary ammonium headgroup was synthesized from the methyl ester of vernolic acid as the starting material. The triple-headed derivative could form nonencapsulating structures. Cholesterol was required in the formulation (1:1) to make spherical vesicles that could encapsulate a water-soluble marker. The single-headed derivative, however, formed spherical encapsulating vesicles without cholesterol. TEM, NMR, and FT-IR were used to characterize the vesicles, and molecular structure vs morphology relationships were postulated on the basis of these data. The triple-headed amphiphile also formed a DNA complex that was highly resistant to hydrolysis by DNase. This amphiphile-DNA complex was used as vector for gene transfer in cell culture demonstrating efficient DNA transfection.     

Preparation of Fine Alumina Powders by Hydrolysis of Aluminum Isopropylate

Preparation of fine alumina powder by hydrolysis of aluminum isopropylate was studied.