CALCULATION OF VAPOR PRESSURES FROM MODEL FRAGRANCE EMULSIONS DURING EVAPORATION

The vapor pressure data from previous publications of a model fragrance emulsion system consisting of water, an aromatic fragrance phenethyl alcohol, an aliphatic one limonene, and a nonionic surfactant Laureth 4, were used to calculate the variation in vapor pressures of both fragrances and water during free evaporation. The evaporation path in a three-dimensional four-component phase diagram was estimated from the vapor pressures.

The results showed as expected that the high note fragrance compound evaporates first followed by water and the low note one. Unexpectedly, it was found that vapor pressure of low note fragrance, phenethyl alcohol, is significantly increased during evaporation.     

ASSOCIATION STRUCTURES OF MIXED BLOCK COPOLYMERS OF DIFFERENT POLAR CHAIN LENGTH

The amphiphilic association structures in the system water-phenethyl alcohol and two triblock copolymers (L101: EO_4.5PO₅₉EO_4.5 and F108: EO_132.5PO₅₀EO_132.5) (EO=ethylene oxide, PO=propylene oxide) were investigated by optical observation, measurements of surface tension, quasi-elastic light scattering and electric conductance. The results showed a most drastic influence of small amounts of the long polar chain block copolymer on the phase regions in the system water-phenethyl alcohol - (EO)₅(PO)₅₆(EO)₅ with 0.1% of the long polar chain compound added to the short chain one giving a most pronounced change in the phase regions.     

A structural study of the mesophases of two oxyethylene alkyl ether-decane-water systems,a comparison between technical grade C12EO〈7〉 and pure C12EO6

As part of a study polyoxyethylene alkyl ethers (C _m EO _n ), water and decane, the phase diagram and the structures of the mesophases of pure C₁₂EO₆ and technical grade C₁₂EO₇ were compared. The constructed phase diagrams of the two systems show a great resemblance except for one difference: the viscous isotropic phase is only present in the C₁₂EO₆ phase diagram.The swelling behavior of the lamellar and hexagonal phases was studied with smallangle x-ray scattering. Both the lamellar and hexagonal phases showed an ideal swelling behavior and no differences between the lamellar and hexagonal phases of the two systems were detected.With freeze-fracture electron microscopy the hexagonal and lamellar phases were visualized. No differences in the textures of the lamellar phases were found, however, the micrographs of the hexagonal phases of the two systems clearly showed different textures. While in the hexagonal phase of the C₁₂EO₆ system only infinite long rods were visualized, short interrupted rods were found in the hexagonal phase of the C₁₂EO₇ system.     

Evaporation from Three Single‐Compound Phases in Equilibrium

The evaporation paths in a system of three single‐compound phases in equilibrium were calculated using a phase diagram approach assuming the evaporation rate proportional to the compound's vapor pressure and molecular weight. The variation with time of the weight of the individual phases was linear, while the weight fraction was not. The approach allowed a simple calculation of the fraction of remaining compounds after one of them was exhausted during the evaporation and a convenient graphical illustration of the importance of the relative vapor pressures.     

Phase Behavior of Poly(Oxyethylene)–Poly(Oxypropylene)–Poly(Oxyethylene) Block Copolymer in Water and Water–C12EO5 Systems

Abstract

The binary phase diagram of a triblock copolymer poly(oxyethylene) (PEO) poly(oxypropylene) (PPO) poly(oxyethylene) (PEO), (PEO)₃₇(PPO)₅₈(PEO)₃₇ or P105 in water and the ternary system of P105, water, and pentaoxyethylene dodecyl ether (C₁₂EO₅) has been studied to understand the miscibility of a small amphiphile, C₁₂EO₅ and a copolymer, as well as the mixing effect on the formed liquid crystalline structures. Phase diagrams, small angle x‐ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize these systems. The phase diagram of the binary system is presented together with the characteristic parameters for founded phases, namely, cubic, hexagonal, and lamellar phases. In the ternary system it was found that the small amphiphile and the block copolymer, despite having very different chain lengths are essentially miscible forming single phases. A large amount of C₁₂EO₅ can be solubilized in the P105 aggregates whereas P105 is most difficult to dissolve in the C₁₂EO₅ aggregates because of the difference in the molecular size. The copolymer is practically insoluble in the lamellar phase of C₁₂EO₅ due to the packing constraint. Hence, two lamellar phases coexist in a surfactant‐rich region, at W _s  = 0.66, where W _s is the weight fraction of the total amphiphile in the system. This indicates that the thickness of the lipophilic part of the C₁₂EO₅ lamellar phase is too small to allocate the large lipophilic chain of the P105 triblock copolymer.     

1.3-DITHIOL-2-THION-4.5-DITHIOLAT AUS SCHWEFELKOHLENSTOFF UND ALKALIMETALL

Abstract

Die Reaktion von Schwefelkohlenstoff mit Natrium oder Kalium führt zur Bildung äquimolarer Mengen von 1.3-Dithiol-2-thion-4.5-dithiolat (1) und Trithiocarbonat. Durch Zugabe von ZnCl₂ und NEt₄Br läßt sich (1) stabilisieren. Der entstehende Zink-Komplex ermöglicht die Herstellung von 4.5-Bis(benzoylthio)-1.3-dithiol-2-thion (10), woraus durch Umsetzung mit Basen (1) in quantitativer Ausbeute wieder entsteht. Die Alkylierung von (1) führt zu 4.5-Bis(alkylthio)-1.3-dithiol-2-thionen. (1) is ein neuer, schwefelreicher 1.2-Dithiolat-Ligand. Die Kristallstruktur des Bis-Chelates von (1) mit Ni(II) als (n-Bu₄N)₂-Salz bestätigt die für (1) angenommene Struktur.

The reaction of carbon disulfide with sodium or potassium in dimethyl formamide yields 1,3-dithiole-2-thione-4,5-dithiolate (1) and trithiocarbonate in equimolar amounts. (1) was stabilized by addition of ZnCl₂ and NEt₄Br. The resulting zinc complex enables the isolation of 4,5-bis(benzoylthio)-1,3-dithiole-2-thione (10). (1) can be recovered from (10) by bases with quantitative yield. (1) represents a new multi-sulfur 1,2-dithiolate ligand. The crystal and molecular structure of the bis-complex of (1) with Ni(II) ((n-Bu₄N)₂-salt) confirms the structure of (1).     

A specialized apparatus for the study of liquid crystals at high pressures

Abstract

A pressure system specially designed for the study of liquid crystal materials at high pressures up to 4kbar is presented. The pressure system is based on a hydrostatic screw injector and uses either oil or gas as the pressure transmitting medium. The type of measurements which can be performed with the instrument include polarized microscopy, optical spectroscopy, electrooptic and electrical measurements. The different measurements performed place specific constraints on the design of the apparatus and the pressure cells, and details are given. A preliminary study of the smectic A modification of the twist grain boundary phase (TGB_A) at high pressures is presented. The pressure versus temperature phase diagram shows (i) a negative gradient of the TGB_A/isotropic phase boundary line and (ii) that the TGB_A phase does not exist at pressures above about 250 bar. Following Lubensky's analogy between the TGB_A phase and type II superconductors, the disappearance of the TGB_A phase at high pressure may imply that the Landau-Ginsburg parameter K decreases with pressure.     

High-Yield Synthesis of Gold Microplates Using Amphiphilic Block Copolymers: Are Lyotropic Liquid Crystals Required?

Summary : High-yield synthesis of gold microplates is achieved through autoreduction of hydrogen tetrachloroaureate (III) hydrate (HAuCl₄ · 3H₂O) in aqueous solutions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (Pluronic L64, EO₁₃PO₃₀EO₁₃) at ambient conditions, in the absence of added energy, reductant, or other surfactants. The formation by the amphiphilic block copolymer of lyotropic liquid crystals (e.g., ordered cylindrical/hexagonal or lamellar phases) is not required for templating the formation of such microplates.     

Synthesis of 6-Substituted/Unsubstituted- 7,9-diaryl-1,2,4,8-tetraazaspiro[4.5]- decan-3-thiones

Abstract

Some 2,6-diarylpiperidin-4-one thiosemicarbazones (1a–8a), obtained from the corresponding 2,6-diarylpiperidin-4-ones (1–8) on oxidative cyclization with H₂O₂ at 0°C provide 7,9-diaryl-1,2,4,8-tetraaza spiro[4.5]decan-3-thiones (1b–8b) in excellent yields. The structures of these compounds have been established on the basis of their elemental, analytical and spectral data.     

Mass spectrometric studies of the vapour phase in the (Pu + O) system

Vapour pressure measurements at high temperatures have been performed on plutonium oxide samples using a Knudsen cell coupled with a mass spectrometer. Different experimental conditions were applied for the derivation of the solid–gas phase relations for three composition in the Pu–O phase diagram: the (Pu₂O₃–PuO_2?x) two-phase domain, the congruent vapourisation composition and near stoichiometric PuO_2.00. The partial pressures of the gaseous species PuO₂, PuO, and Pu were assessed from ionisation efficiency curves recorded at constant temperature. The vapour pressure results for different phase fields were discussed together with all the available literature data.     

Fabrication of ZnO Nanorods in Colloidal Systems Formed by PEO‐PPO‐PEO Block Copolymers

One‐dimensional (1‐D) ZnO nanorods with various sizes were synthesized in colloidal systems formed by PEO‐PPO‐PEO block copolymers. The experimental results revealed that the growth of ZnO nanorods was dependent on the molecular structure of polyether. It was known that L64 (EO₁₃PO₃₀EO₁₃) and F68 (EO₈₀PO₃₀EO₈₀) had the same size PPO block but different content of PEO. We concluded that the size of the ZnO products obtained in F68 was larger due to its longer PEO chain.     

CONTINUOUS ABSORPTION OF TOLUENE VAPOR BY MICELLAR SOLUTIONS AND THE RESULTING MICROEMULSIONS

ABSTRACT

Microemulsions consisting of AOT-H₂O-toluene-hexyl carbitol (HC) or butyl carbitol (BC) were investigated in relation to the relative vapor pressure of toluene (P/P_o). The microemulsions generally revealed high (P/P_o). The relatively lower (P/P_o) was only obtained from those containing 10% and 15% AOT at higher levels of HC and BC respectively. From the linear plot of (P/P_o) against the volume fraction of toluene, the transition from micellar solution to microemulsion was evident. This transition phenomenon was also observed in the continuous absorption of toluene vapor. It was concluded chat the microemulsions studied were not efficient in scrubbing toluene vapor, but they were much more effective than their respective micellar solutions.     

The surface pressure effect of pentaoxyethylene and maltoside surfactant head groups

From experimental surface tension data for water solutions of dodecyl-β-maltoside, C₁₂M, and dodecyl-penta-(ethylene oxide), C₁₂EO₅, in the range below the CMC, the corresponding head group surface pressure functions vs. packing density were derived. These functions were compared with theoretical expressions based on some different models of the mixed head group/water film. Tentatively, we concluded that the two-dimensional hard fluid approach provides a convenient starting-point in order to account for the observed surface pressures of both the maltoside and EO head groups.     

Characteristic features of the evaporation of liquids

Abstract

The evaporation rate variation of liquids (water, ethanol) is studied versus their vapour pressure. From measurements of liquid-vapour interface displacement versus time, the state change whose rate is v_o at initial time-is seen to slow down before reaching a constant rate v₁ under stationary working conditions. The difference between both rates increases as pressure decreases. In addition, whereas the v_o(P) curves are monotonous and increasing from saturation vapour pressure to vacuum, the v₁(P) curves have a typical shape, characterised by two extremums.

From the simultaneous measurement of temperature to assess the endothermic character of state change, it is shown that the previous observations may be related to the occurrence of a thermal flow at interface level.

The new profile of the v₁(P) curves can neither be predicted nor explained from conventional expressions of evaporations rate. The present paper shows that a thermodynamic interface model involving coupling of mass and heat flows allows the features detected to be accounted for with out any ambiguity.     

High pressure differential thermal analysis of nematic compounds with different molecular shapes

Abstract

By means of high pressure differential thermal analysis we measured the pressure/temperature phase diagrams of several nematic compounds with different molecular structures. Using pressures up to about 500 M Pa we found strongly nonlinear clearing curves. This behaviour is interpreted as changes from ‘weak’ intermolecular potentials to ‘hard’ potentials, or using thermodynarmic arguments, strong pressure dependence of the volume discontinuity at the clearing transitions.     

Multivariate Association of Graph-Theoretic Variables and Physicochemical Properties

Abstract

We used canonical correlation analysis to examine the multivariate association between two distinct data sets commonly measured or calculated for approximately 600 chemicals: (1) measured or calculated values of select physieochemical properties (i.e., K _ow, boiling point, heat of vaporization, molecular weight, water solubility, molecular volume, hydrogen bonding potential, and vapor pressure) and (2) calculated algorithmically-derived variables (i.e., topological and neighborhood indices derived from graph theory). Canonical correlation analysis identified eight highly significant associations between linear combinations of graph-theoretic variables and linear combinations of physicochemical properties. The set of graph theoretic variables was significantly related to all physieochemical properties, explaining 55% to 99% of the variation in these properties.     

On the Degree to which the Contact Angle is Affected by the Adsorption onto a Solid Surface of Vapor Molecules Originating from the Liquid Drop

ABSTRACT

From surface tensions of liquids and Lifshitz-van der Waals (LW) and Lewis acid-base (AB) surface tension components and the AB electron-acceptor γ⁺ and electron-donor γ^˙ parameters determined by contact angle (θ) measurements (using the Young-Dupré equation for polar systems), the interfacial work of salvation (W_st) between various contact angle liquids (L) and a moderately polar solid (S), such as polymethylmethacrylate (PMMA) could be determined. From these W_SL -values the maximum values of the equilibrium association constant, K_a, are obtained for the adsorption of molecules of liquids, L, onto a solid substratum, S. From the K_a-values and the vapor pressures of the various liquids, the maximum number of liquid molecules adsorbed from the gaseous phase onto the solid surface can be determined, at 20^°C and 76cm Hg ambient atmospheric pressure. This yields the maximum value for the fraction, ?, of the surface area of the solid that will be covered by molecules of the liquid, L, emanating from the liquid drop, via the gaseous state. From these ?-values, using Cassie's approach, the maximum amount, Δθ, can be determined by which the observed contact angle is lower than the ideal contact angle, as a consequence of the coverage of the solid substratum by adsorbed molecules originating from the contact angle liquid.

For most of the contact angle liquids used, the maximum deviation, Δθ, is well under 1^°; for water on PMMA it is about 1½^°.     

Aggregation Behavior of Pluronic-L64 in Presence of Sodium Dodecyl Sulphate in Water

The effect of sodium dodecyl sulfate (SDS) on the micellization and aggregation behavior of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO₁₃ PO₃₀ EO₁₃) have been investigated by various techniques like, cloud point, viscosity, isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), fluorescence spectroscopy, room temperature phosphorescence (RTP), and small angle neutron scattering (SANS). Addition of SDS in L64 solutions shows mark alteration of different properties. We observed synergistic interaction between SDS and Pluronic L64. The changes in the critical micelle concentration (CMC), critical micelle temperature (CMT), cloud point (CP), micelle size, and shape has been correlated and reported in terms of structure dynamics and mechanics. The ITC titrations have been used to explore the different stages of binding and interactions of SDS with L64. The enthalpies of aggregation for copolymer-SDS aggregates binding, organizational change of bound aggregates, and the threshold concentrations of SDS in the presence of copolymer were estimated directly from ITC titration curves. The effect of temperature on enthalpy values has been reported in terms of different aggregation state. Fluorescence and RTP for L64 were used to investigate the change in micellar environment on the addition of SDS at different temperature. Appearance and shifting of SANS peaks have been used to monitor the size and inter micellar interaction on addition of SDS in L64 solution. Cloud point and viscosity elaborate the penetration of SDS molecule in L64 micelle and hence changing the micellar architect.     

Hexafluoropropylene Oxide–Alcohol: A Convenient System for Silica Dissolution

Abstract

A new method of silica dissolution is described. It involves the formation of a stable SiF₄ · n ROH complex (1, 1a) just from SiO₂ and anhydrous alcoholic HF generated in situ from commercially available hexafluoropropene oxide. Alcoholic SiF₄ complexes can be easily converted to different organosilicon compounds of the type SiF₄L₂ and (LH)₂SiF₆ [L = 1,10-phenantroline (2a), 2,2′-dipyridyl (2b), Me₂SO (2c), pyridine (2d), triethanolamine (3a)]. Different silica-containing compounds can be used in this strategy—silicagel, sand, alumosilicates, and even rice husk.

GRAPHICAL ABSTRACT     

The Homogeneity Range of Crystalline Tris(8-hydroxyquinoline)gallium

An experimental procedure has been developed for constructing p _i –T diagrams (partial vapor pressure of the ligand-forming component–temperature) for luminescent metal complexes with symmetric organic ligands. The partial 8-hydroxyquinoline vapor pressure–temperature diagram has been constructed for tris(8-hydroxyquinoline)gallium electrophosphor (Gaq₃) in the temperature range 300–617 K at 8-hydroxyquinoline vapor pressures 10^–3–10⁴ Pa, where the homogeneity ranges of different Gaq₃ polymorphs have been determined. Structure-sensitive properties of crystalline materials can be tailored by changing synthesis conditions within the homogeneity range of a phase.