The Synthesis of Cyclotriphosphazene Liquid Crystals

Generally,thermotropicliquidcrystalsareconstructedoforganiccomPoundsofanisotropicshaPe.Inthesearchfornewmoleculardesignsformesogensoforiginalshapes,onecanroughlyfollowtwodirections.Thefirstideaistovarythenumberofalkylchainsgraftedaroundagivencore.Thesecondideaofshapemodificationconsistsintheformationofclustersofafewidenticalmesogens,generallyatwin.Accordingtothesetwoideas,manynewkindsofliquidcrystalshavebeensysthesized.Hexakis(4-(4'-alkoxy)biphenoxy)cyclotriphosphazeneswerethemostinteresting…     

Photostability of Octyl‐P‐Methoxy Cinnamate in O/W Emulsions and in SLNs Vehicled in the Emulsions

The photochemical degradation of the sunscreen p‐octyl‐methoxy‐cinnamate (OMC) was studied in different media: Finsolv TN (a fluid ester), O/W emulsion and gel‐emulsion. OMC photolysis was performed using an UVB lamp and the degradation kinetic was studied in presence of various initial concentration of the active. The study was performed comparing the naked to the SLNs form of the active and the experiments were monitored with HPLC/UV‐VIS apparatus. Results suggest that lower is the concentration of the UVB sunscreen in the formulations more pronounced is its photodegradation rate. In all the cases the inglobation of OMC into SLNs leads to an over additive UV‐blocking effect.     

W/O/W Multiple Emulsions Obtained by One‐Step Emulsification Method and Evaluation of the Involved Variables

The effects of some composition variables on the development of multiple emulsions by one‐step method were evaluated and their morphology characterized. The formulations that remained stable during the period of the test were submitted to centrifugation and thermal stress tests. The stability and the morphology of multiple droplets were affected not only by the type and concentration of the surfactants employed, but also by the water/oil ratios used. The results suggest that the formation of multiple droplets could involve a combination of transitional and catastrophic phase inversions. The results provide improved knowledge about the one‐step emulsification method, a simplified process to prepare multiple emulsions when compared to the two‐steps method.     

Factors Affecting the Droplet Size of Water‐in‐Oil Emulsions (W/O) and the Oil Globule Size in Water‐in‐Oil‐in‐Water Emulsions (W/O/W)

Multiple emulsions of the W₁/O/W₂ type are promising tools for encapsulating bioactive ingredients in the inner aqueous droplets. It is necessary, however, to control the factors influencing their encapsulation efficiency. One important factor is the particle size because it determines the surface area available for mass transport. Because of the coexistence of water and oil droplets in multiple emulsions, there are numerous factors that have an impact on particle size, for example, oil phase composition, interfacial properties, and viscosity of the phases. The purpose of this study was to systematically investigate the effect of these factors on particle sizes in multiple emulsions.     

Liquid chromatographic study of two methoxypsoralen isomers with β-cyclodextrin

Abstract

The inclusion into β-cyclodextrin (β-Cyd) by the two methoxypsoralen isomers (5-methoxypsoralen (5-MOP) and 8-methoxypsoralen (8-MOP)) has been extensively studied by reverse phase liquid chromatography (RP-HPLC). Some important quantitative data concerning the complexation in a dynamic flow system have been drawn. The stoichiometry of the complex formation (1:1 in all instances), and the affinity constants with the β-Cyd cavity (K_f) of the two guest compounds, have been established. By taking into account the competitive effect of the organic modifier of the eluent (methanol), the K_fs of both compounds have been extrapolated to pure water (233 M^?1 and 106 M^?1 for 5-MOP and 8-MOP, respectively). On the other hand, the established stoichiometry and affinity constants have been interpreted in terms of enthalpy and entropy changes. Finally, the importance of the position of the methoxy substituent has been underlined and seems to rule the quality of the fit of each isomer within the inner cavity of β-cyclodextrin.     

Preparation and characterization of W/O/W type double emulsion containing PGPR–lecithin mixture as lipophilic surfactant

The objective of this study is to produce double emulsion by combining polyglycerol polyricinoleate (PGPR) with lecithin as lipophilic surfactant. Although lecithin alone produced only oil-in-water type emulsion, the mixture of lecithin and PGPR could produce water-in-oil type emulsion as well. Moreover, different emulsification treatments were applied to study the influence of homogenization methods on the physicochemical characteristics. The obtained double emulsions were compared in terms of stability and droplet size. It was found that the homogenization method influenced the physiochemical characteristics of the double emulsion and the most stable double emulsion with the smallest droplet size was obtained by high-speed homogenization method.     

Iron-catalyzed hydroxylation of β-ketoesters with hydrogen peroxide as oxidant

The hydroxylation of β-ketoesters was studied using simple iron catalysts and 30 wt % hydrogen peroxide as the terminal oxidant. The highest activity and yield were achieved in the presence of iron(III) chloride. Cyclic β-ketoesters could be smoothly hydroxylated in 75-90% yield. For linear β-ketoester and β-ketoamide, the chloro-substituted products were obtained.     

Synthesis and Characterization of Star-like Liquid Crystals Centered by Silicon

The synthesis and characterization of two new star-like liquid crystals are reported. They are made of a silicon core and four alkoxyazobenzene monomers in the periphery. Theirp hase behaviors and the structures are determined by infrared absorption spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), elemental analysis (EA), polarizing optical microscope (POM) and differential scanning calorimetry (DSC).     

Comparison of Aqueous and 1-Octanol Solubility as well as Liquid–Liquid Distribution of Acyclovir Derivatives and Their Complexes with Hydroxypropyl-β-Cyclodextrin

The aim of the presented work is the comparison of aqueous and 1-octanol solubilities of different acyclovir derivatives and their hydroxypropyl-β-cyclodextrin inclusion complexes. The solubility measurements were carried out at different temperatures over the range 25–45 °C using water, 1-octanol, water saturated with 1-octanol, 1-octanol saturated with water, buffered aqueous solutions (pH = 5.5 and 7.0) and buffered aqueous solutions containing cyclodextrin as solvents. The aqueous solubilities of the compounds are very low but may be enhanced by complexation with hydroxypropyl-β-cyclodextrin, especially if the acyclovir derivatives have aromatic groups which may be included in the cyclodextrin cavity. The values of 1-octanol–water partition coefficients of acyclovir derivatives, obtained using extraction experiments, showed a similar sequence as the solubility results in 1-octanol. Additionally, some molecular mechanics and molecular dynamic calculations were performed to determine optimized structures of acyclovir derivative complexes with β-cyclodextrin treated as a model.     

Study of Liquid‐Crystalline Phase Changes during Evaporation in Vegetable Oil Emulsions

During evaporation, the rate between volatile and nonvolatile components in an emulsion changes. In this study, emulsions of marigold and canola oil were made according to a phase diagram, simulating the decreasing water amount that happens when the water evaporates from an emulsion. In addition, two basic emulsions were submitted to evaporation and then to microscopic analysis to compare the results of both tests. It was observed that when the water rate decreases, the liquid‐crystalline phase changes its organization, reaching a proportion that it is not hydrated anymore, having a solid aspect. Moreover, these emulsions submitted to evaporation remained to show lamellar phase even when there was no water in the formulation. This is interesting to understand the behavior of an emulsion after it is applied under the skin.     

Polymerization and Copolymerization of Some Monomers as Adducts with β-Cyclodextrin

The feasibility of chemical bond formation, especially in the chain-transfer reaction between polymer and β-cyclodextrin (β-CD) molecules in the products of the radiation polymerization of β-CD with vinylidene chloride (VDC) its adducts has been considered. The lack of these bonds in the polymerization products of similar β-CD adducts with methyl methacrylate (MM), styrene (St), a mixture of VDC and allyl chloride (AC) and a mixture of VDC and MM (10:90 molar ratio) has been established. On the basis of the results obtained the lack of chemical bonds in the polymerization product of β-CD· VDC adduct is suggested.     

An Ionic Liquid Loaded β-Cyclodextrin-Cross-Linked Polymer as the Solid Phase Extraction Material Coupled with High-Performance Liquid Chromatography for the Determination of Rhodamine B in Food

A novel method for separation and determination of rhodamine B in food samples is described. The work is based on the utilization of an ionic liquid loaded β-cyclodextrin cross-linked polymer coupled with high-performance liquid chromatography for the determination of rhodamine B. The inclusion interaction of the ionic liquid-β-cyclodextrin cross-linked polymer with rhodamine B was studied by FTIR. Under optimum conditions, the preconcentration factor achieved for this method was approximately 20. The linear range, detection limit, and relative standard deviation were 0.80 to 130.0 µg L^?1, 0.09 µg L^?1, and 0.66% (n = 3, concentration = 10.0 µg L^?1), respectively. The technique was successfully applied for determination of rhodamine B in food samples.     

Liquid crystal polymorphism of boron difluoride β-diketonates

Boron difluoride 2-alkyl-β-diketonates possessing liquid crystal polymorphism and luminescence properties were first obtained. Influence of the ligand structure on the liquid crystal properties of the boron difluoride complexes was demonstrated.     

W/O与O/W，W/O与双连续结构微乳液的界面电性质

无探针伏安法和电容法测定结果表明,在质量比H_2O/n-C_5H_(11)OH = 50/50条件下,SDS总含量<3%时,上相呈W/O结构,下相呈O/W结构,随着体系SDS 总含量的增大,界面上SDS量增加,界面电势ΔE、界面电容C、界面电荷传递电流 i_p均增加,而界面电阻率ρ_i则减小;当体系 SDS总含量≥3%时,上相呈W/O结构 ,下相呈双边续结构,各界面电性质变化幅度均变缓。     

Simultaneous Control of pH and Ionic Strength during Interfacial Rheology of β-Lactoglobulin Fibrils Adsorbed at Liquid/Liquid Interfaces

Proteins can aggregate as amyloid fibrils under denaturing and destabilizing conditions such as low pH (2) and high temperature (90 °C). Fibrils of β-lactoglobulin are surface active and form adsorption layers at fluid-fluid interfaces. In this study, β-lactoglobulin fibrils were adsorbed at the oil-water interface at pH 2. A shear rheometer with a bicone geometry set up was modified to allow subphase exchange without disrupting the interface, enabling the investigation of rheological properties after adsorption of the fibrils, as a function of time, different pH, and ionic strength conditions. It is shown that an increase in pH (2 to 6) leads to an increase of both the interfacial storage and loss moduli. At the isoelectric point (pH 5-6) of β-lactoglobulin fibrils, the maximum storage and loss moduli are reached. Beyond the isoelectric point, by further increasing the pH, a decrease in viscoelastic properties can be observed. Amplitude sweeps at different pH reveal a weak strain overshoot around the isoelectric point. With increasing ionic strength, the moduli increase without a strain overshoot. The method developed in this study allows in situ subphase exchange during interfacial rheological measurements and the investigation of interfacial ordering.     

Rate constants for the gas-phase reactions of OH and O3 with β-ocimene, β-myrcene, and α- and β-farnesene as a function of temperature

The rate constants for the gas-phase reactions of hydroxyl radicals and ozone with the biogenic hydrocarbons β-ocimene, β-myrcene, and α- and β-farnesene were measured using the relative rate technique over the temperature ranges 313-423 (for OH) and 298-318 K (for O?) at about 1 atm total pressure. The OH radicals were generated by photolysis of H?O?, and O? was produced from the electrolysis of O?. Helium was used as the diluent gas. The reactants were detected by online mass spectrometry, which resulted in high time resolution, allowing large amounts of data to be collected and used in the determination of the Arrhenius parameters. The following Arrhenius expressions have been determined for these reactions (in units of cm3 molecules?1 s?1): for β-ocimene + OH, k = (4.35(-0.66)(+0.78)) × 10?11 exp[(579 ± 59)/T]; for β-ocimene + O?, k = (3.15(-0.95)(+1.36)) × 10?1? exp[-(626 ± 110)/T]; for β-myrcene + O?, k = (2.21(-0.66)(+0.94)) × 10?1? exp[-(520 ± 109)/T]; for α-farnesene + OH, k(OH) = (2.19 ± 0.11) × 10?1? for 23-413 K; for α-farnesene + O?, k = (3.52(-2.54)(+9.09)) × 10?12 exp[-(2589 ± 393)/T]; for β-farnesene + OH, k(OH) = (2.88 ± 0.15) × 10?1? for 323-423 K; for β-farnesene + O?, k = (1.81(-1.19)(+3.46)) × 10?12 exp[-(2347 ± 329)/T]. The Arrhenius parameters here are the first to be reported. The reactions of α- and β-farnesene with OH showed no significant temperature dependence. Atmospheric residence times due to reactions with OH and O? were also presented.     

Self-Assembly of Aminocyclopropenium Salts: En Route to Deltic Ionic Liquid Crystals

Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self-assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction provided insight into the unique self-assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p-alkoxyphenyl units led to bilayer-type smectic mesophases, wedge-shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed.     

Lamellar Liquid Crystals of Brij 97 Aqueous Solutions Containing Different Additives

Lamellar liquid crystals of Brij 97 aqueous solutions were investigated by means of rheological techniques and SAXS at 25 °C, in the presence of various additives including isopropyl myristate, oleic acid, ionic liquid bmim-PF₆ and bmim-BF₄. The lamellar phases show high elasticity as indicated by their mechanical and discrete relaxation spectra, which is expected to be an advantage when they are used as drug delivery vehicles. It is noted that in comparison with other systems, the lamellar phase formed in the Brij 97/water/IPM system has the lowest storage and loss moduli, implying that it has a weak network strength and less stable internal structure. The Brij 97/water/oleic acid system is the most shear resistance, whereas the Brij 97/water/bmim-PF₆ system exhibits fluid-like viscoelastic properties to some extent. These differences are analyzed through SAXS data for the different location of the additive in the lamellar phase.     

W/O/W多重乳液中水传递的控制

建立了简化的W/O/W(水/油/水)多重乳液乳珠模型——统计平均半径模型, 预测出当W/O/W多重乳液内水相水滴之间以及内外水相之间均达到水传递平衡时的内外水相中盐的浓度, 从而实现对水传递的控制, 以维持W/O/W多重乳液的稳定. 按理论预测制备出了不同稳定态的W/O/W多重乳液, 利用差分扫描量热仪(DSC)检测了多重乳液中水的传递过程, 确定体系在实验状态下的稳定程度, 实验结果与理论预测基本吻合.     

Microwave-Assisted Extraction/Dispersive Liquid–Liquid Microextraction Coupled with DSI-GC-IT/MS for Analysis of Essential Oil from Three Species of Cardamom

A novel method of microwave-assisted extraction coupled with polyethylene Pasteur-pipette-based dispersive liquid–liquid microextraction applying low-density organic solvent (MAE-LDS-DLLME) was successfully developed for extraction and preconcentration of essential oil from three species of cardamom (Semen Alpiniae Katsumadai, Fructus Amomi Rotundus, and Semen Myristicae). The essential oil was analyzed by gas chromatography-ion trap/mass spectrometry (GC-IT/MS) using a ChromatoProbe direct sample introduction (DSI) device. The effects of various parameters affecting the extraction process, such as the type of extraction solvent and dispersive solvent, ionic strength, microwave power, and irradiation time, were investigated thoroughly and optimized. The optimal conditions were extraction solvent of toluene, dispersive solvent of methanol, microwave power of 80 W, irradiation time of 4.0 min, plant material amount of 0.1 g, and no addition of salt. Compared with hydrodistillation, MAE-DLLME-DSI-GC–MS is a simple, rapid, low-cost, efficient, and environmentally friendly method, and the essential oil contains higher amounts of oxygenated compounds, which play an important and valuable role in terms of their contribution to the fragrance of the essential oil. In this work, we also studied the main components of the three varieties of cardamom. Qualitative and quantitative differences in the components of the three essential oils were found to be present. Based on comparison of the main bioactive compounds of essential oil, a significant difference was found between Semen Alpiniae Katsumadai or Fructus Amomi Rotundus and Semen Myristicae. This study also provides a new approach for quality assessment of traditional Chinese medicines.