Studies of structures of poly-ε-caprolactam/montmorillonite nanocomposite: Part 1. Tests of compression moulded specimens

A poly-ε-caprolactam (PA6) taken as a reference and its nanocomposite (PNC) containing 1.6 wt.% of montmorillonite were examined. The specimens as discs were prepared by compression moulding at 235 °C and 70 MPa. Using the novel version of TMA, in the PA6 and PNC specimens, within the temperature range from −100 to 250 °C, a semi-crystalline structure with anisotropy of distribution of the more ordered (crystalline?) portion was found in the surface layer up to 0.5 mm thick. The amorphous regions have differed in a state of order (different transition temperatures) and related compactness. The free volume fraction in amorphous regions determined in machine direction (normal to the surface) is increased when in transverse direction is reduced; simultaneously molecular weights of polymer chains between junctions were increased by incorporation of the nanofiller.     

Polymer/montmorillonite nanocomposites with improved thermal properties: Part I. Factors influencing thermal stability and mechanisms of thermal stability improvement

The results of recent research indicate that the introduction of layered silicate - montmorillonite - into polymer matrix results in increase of thermal stability of a number of polymer nanocomposites. Due to characteristic structure of layers in polymer matrix and nanoscopic dimensions of filler particles, several effects have been observed that can explain the changes in thermal properties. The level of surface activity may be directly influenced by the mechanical interfacial adhesion or thermal stability of organic compound used to modify montmorillonite. Thus, increasing the thermal stability of montmorillonite and resultant nanocomposites is one of the key points in the successful technical application of polymer-clay nanocomposites on the industrial scale. Basing on most recent research, this work presents a detailed examination of factors influencing thermal stability, including the role of chemical constitution of organic modifier, composition and structure of nanocomposites, and mechanisms of improvement of thermal stability in polymer/montmorillonite nanocomposites.     

Making equation of state models predictive: Part 2: An improved PCP-SAFT equation of state

We use the PCP-SAFT equation of state, which is of the Van der Waals type and has a sound physical basis, to predict mixture properties, such as vapor–liquid and liquid–liquid equilibria, as well as excess enthalpies. We use molecular properties, such as dipole moment, quadrupole moment, polarizability and dispersion interaction coefficients, that have been determined quantum mechanically in Part I of this publication and adjust the remaining three pure compound parameters to pure compound data. We finally present a new combination rule for the dispersion energy parameter ? that is based on the quantum mechanically determined data. The predictions based on quantum mechanically determined pure compound properties along with the new combination rule show an improved performance compared to the original PCP-SAFT combination rule.     

Analysis of polyethoxylated surfactants in microemulsion-oil-water systems: Part II

Commercial ethoxylated surfactants are always a mixture of oligomers with different ethylene oxide number (EON). The different oligomers were separated by high performance liquid chromatography (HPLC) on an amino column using a mixture of polar and nonpolar mobile phases. Surfactant oil-water-systems were studied according to the unidimensional scan technique. The surfactant content in the oil, microemulsion and water phases was determined by UV spectroscopy and HPLC. The partitioning of the surfactant oligomers in the oil and water phases of a Winsor III system was determined. The effect of different salts on the surfactant partitioning is discussed.     

Fluoroalkene chemistry: Part 2. Reactions of thiols with some toxic 1,2-dichlorinated polyfluorocycloalkenes

1,2-Dichlorotetrafluorocyclobutene, 1,2-dichlorohexafluorocyclopentene and 1,2-dichlorooctafluorocyclohexene were treated with an equimolar amount of benzenethiol, 2-methoxybenzenethiol, 3-methoxybenzenethiol and 4-methoxybenzenethiol in acetonitrile with potassium carbonate. Each combination of fluoroalkene and thiol gave a mixture of mono and bis vinyl substitution products whose proportions depended on the ring size of the fluorocycloalkene and the size and electronic characteristics of the thiol. Treatment of 1,2-dichlorotetrafluorocyclobutene with one or two molar equivalents of N-acetylcysteine isopropyl ester in acetonitrile with potassium carbonate produced the mono and bis vinyl substitution products accordingly. The results support the contention that the high inhalation toxicity of the fluorocycloalkenes is due to reaction with two molar equivalents of biological thiols in the lung.     

Polyhalogenated heterocyclic compounds: Part 52. [1] Macrocycles from 3,5-dichloro-2,4,6-trifluoropyridine

Model studies show that displacement of fluorine, rather than chlorine, occurs upon reaction of 3,5-dichloro-2,4,6-trifluoropyridine with sodium methoxide and phenoxide. Subsequent hydro-dechlorination can be achieved by reaction with lithium aluminium hydride whereas reaction of sodium in iso-propanol leads to formation of the tri-iso-propoxy pyridine derivative, via nucleophilic substitution of the methoxy group, rather than the dechlorinated products. Macrocycles can be synthesised by reactions of appropriate difunctional oxygen nucleophiles with 3,5-dichloro-2,4,6-trifluoropyridine, one of which was characterised by X-ray crystallography.     

Approaches to separation interfaces: Electrostatic interaction and local structures of ions at zwitterionic interface

The interaction and separation of ions with zwitterionic layers are reviewed principally based on a series of the author's work. An electrostatic model has allowed us to discuss the chromatographic retention of ions on the zwitterionic stationary phase, and has revealed the ionic interaction occurring at the zwitterionic interface. Similar consideration is applicable to the ionic partition into zwitterionic micelles having the spherical dimension. In the electrostatic models, ion association and solvation changes of ions have been assumed to explain the selectivity in ion recognition. Both assumptions are applicable to polarizable large ions, whereas the former cannot account for the results obtained for small and well-hydrated ions (Cl⁻ and Br⁻). A special X-ray absorption finestructure (XAFS) measurement, which allows selective access to ions interacting with surface monolayers, has been developed, and applied to ions attracted by a zwitterionic monolayer. The X-ray absorption spectra suggest that Zn²⁺ attracted by the zwitterionic monolayer is still hydrated. In contrast, the direct interaction of Br⁻ has been confirmed, indicating that the electrostatic model involving either ion association or the solvation change of an ion does not properly explain the observed phenomena but both effects should be taken into consideration.