Solutions Of Polyoxyethylene Research Articles

Preparation and characterization of concentrated γ-Oryzanol nanodispersions by solvent displacement method: Effect of processing conditions on nanoparticles formation

Concentrated γ-Oryzanol nanodispersions were prepared by solvent displacement method, using purified water (no emulsifier) or aqueous solutions of polyoxyethylene (20) sorbitan monooleate (T80), modified lecithin (ML) or sodium caseinate (SC) as emulsifiers. The nanodispersions had comparable particle sizes (126–157 nm), particle size distribution (monomodal), polydispersity index (˂ 0.1), γ-Oryzanol concentration (1.69–1.82 mg mL−1) and encapsulation efficiency (89.39–98.78%) at optimized processing conditions. Moreover, they had negative ζ-potentials, independently of the composition of the aqueous phase added, indicating that both γ-Oryzanol and emulsifier contributed to nanoparticles formation. Comprehensively, emulsifier-free nanodispersions had a ζ-potential of −46.7 mV, originating potentially from the dissociation of hydroxyl groups of caffeic acid and/or ferulic acid on γ-Oryzanol structures. ML and SC provided negative charges as expected, while T80 stabilized nanoparticles were also charged (−26.0 mV) despite the absence of ionizable groups on polysorbate structure. These results feature the self-stabilizing properties of γ-Oryzanol in concentrated colloidal systems, such as nanodispersions, and present a novel approach for its encapsulation in caloric-free formulations.

Studies of Thermo-acoustical Properties of Polyoxyethylene (20) cetyl ether (Brij-58) in Presence of Additives at Different Temperatures

The measurement of ultrasonic velocity and density as a function of temperature and concentration of additives were carried out. The variation of ultrasonic velocity and density of micellar solution of Polyoxyethylene (20) cetyl ether (Brij-58, CMC= 0.0086% w/v) in the presence of polymer PVP and PEO were studied at 298.15, 303.15, 308.15 and 313.15K. Various acoustic parameters such as adiabatic compressibility (?ad), molar volume (Vm), intermolecular free length (Lf), acoustic impedance (Z) and surface tension (?) of aqueous solution of Brij-58 and Brij-58-polymer mixed solutions were derived from these data. The results were discussed on the basis of polymer-surfactant interactions and hydrophobic interaction, which in turn depends upon the structural arrangement of the linkages involved and difference in the chain which binds the hydrophobic and hydrophilic group in the studied surfactant molecule. It was noted that the ultrasound velocity decreases with increase in temperature. The decrease in the value of ?ad and Lf with increase in ultrasonic velocity indicates that there is significant interaction between the surfactant molecule and added polymer PVP and PEO.

Synthesis of fluorapatite nanopowders by a surfactant-assisted microwave method under isothermal conditions

Fluorapatite nanopowders with different amounts of fluoride ions were prepared using the surfactant-assisted microwave method under isothermal conditions. Microwave irradiation was applied for the rapid formation of crystals. A micellar solution of polyoxyethylene (23) lauryl ether was used as a regulator of nucleation and crystal growth. Characterization studies from X-ray diffraction, field-emission scaning electron microscopy and Fourier-transform infrared spectra showed that crystals have an apatite structure and particles of all samples are nano size, with an average length of 50 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that synthesized fluorapatite nanopowders exhibit activity against tested pathogens: Escherichia coli, Staphylococcus aureus and Candida albicans. Activity increased with the amount of fluoride ions. The synthesized fluorapatite nanomaterials are promising as materials in environmental protection and medicine for orthopedics and dental restorations.

A facile, efficient and “green” route to pH-responsive crosslinked poly(methacrylic acid) nanoparticles

The synthesis of hydrophilic crosslinked poly(methacrylic acid) (PMAA) nanoparticles usually involves the use of organic solvents. In this study, a novel, facile and efficient route was developed for the “green” fabrication of PMAA nanoparticles in water. Crosslinked PMAA nanoparticles were prepared via simply copolymerizing MAA with crosslinker N,N′-methylenebisacrylamide in an aqueous solution of polyoxyethylene (20) sorbitan monolaurate (tween 20), sodium dodecylsulfate and 2,2′-azodiisobutyronitrile. The water-soluble PMAA chains produced in-situ are converted into water-insoluble PMAA/tween 20 complexes via hydrogen bonding interactions with tween 20. This leads to the homogenous nucleation and deposition growth of PMAA nanoparticles, thus realizing the fabrication of crosslinked PMAA nanoparticles in water. Crosslinked PMAA nanoparticles with a z-average hydrodynamic diameter in the range of 99–480nm and a normalized swelling ratio in the range of 1.3–3.1 were obtained by varying the reaction parameters. The pH-sensitivity, biocompatibility and carboxyl functional groups make the crosslinked PMAA nanoparticles ideal candidates for various biomedical applications.

Theoretical Evaluation of Rheological State of Sand Cement Composite Systems with Polyoxyethylene Additive Using Topological Dynamics Concept

Presents the results of studies of contemporary materials in the field of rheological state. The topological mortar structure has been provided by theoretical evaluation of the rheological state of the cross-linked solutions and the experimental viscosity data of the sand cement mortar which has been modified by water-soluble additive – polyoxyethylene. The general model has been made for the structure of non-Newtonian liquideous systems including dilatant, pseudoplastic bodies with two main rheological active components in their structure – rigid and viscous phases. It is shown that in pseudoplastic systems, as the shear stress increases, the viscous phase grows because of the reduction of rigid phase content. In dilatant systems the converse situation has been observed. Furthermore, these phases are not clearly distinguishable, but to the contrary they are spatially interconnected in a complex way. The structure modeling has been made for non-Newtonian bodies using the Shklovskii-de Gennes model. The studies have found that the construction composite sand cement system is defined as the pseudoplastic body where cement and sand act as the rigid phase, water solution of polyoxyethylene – as the viscous phase. These findings can be used to prove the influence of polymer powder on the workability of dry mortar.

Biopartitioning micellar chromatography as a predictive tool for skin and corneal permeability of newly synthesized 17β-carboxamide steroids

In this paper, human skin and corneal permeability of twenty-two newly synthesized 17β-carboxamide steroids was predicted using biopartitioning micellar chromatography (BMC). These compounds are potential soft glucocorticoids with local anti-inflammatory activity when applied to the skin or eye. BMC systems are used to simulate physicochemical properties of human skin (BMC-skin) and cornea (BMC-cornea). Micellar mobile phase, consisted of 0.04M solution of polyoxyethylene (23) lauryl ether (Brij 35), was prepared at different pH values – 5.50 (BMC-skin) and 7.50 (BMC-cornea). Retention factors (k), obtained by use of BMC, were calculated for all newly synthesized 17β-carboxamide steroids as well as for parent glucocorticoids (hydrocortisone, prednisolone, methylprednisolone, dexamethasone and betamethasone). Good correlation was obtained between BMC-skin retention factors and permeability coefficients calculated by use of the artificial membrane that simulates stratum corneum of the human skin. Quantitative structure–retention relationship (QSRR) study was performed in order to explain retention factors of these compounds in the tested BMC systems. ANN-QSRR(k), PLS-QSRR(k) and MLR-QSRR(k) models, created by use of BMC-skin retention data, were compared and optimal model (PLS-QSRR(k)) was selected. Molecular descriptors of the selected model indicate that lipophilicity and number of short CC fragments of tested compounds have the strongest influence on the retention in the BMC-skin system and presumably on their in vivo permeability through human skin. The same model can be applied to the BMC-cornea system and the same conclusion can be drawn for corneal permeability. This model could be used as a predictive tool for the synthesis of novel 17β-carboxamide steroids with desirable permeability through human skin or cornea, depending on their potential pharmacological application.

Salinity Effect in Cloud Point Phenomena by Nonionic Surfactants Used in Enhanced Oil Recovery Tests

The cloud point phenomenon for solutions of polyoxyethylene (POE)-type nonionic surfactants (B, C, D, and E) in different salt concentrations was investigated. The cloud point temperature, T c , increased with elongation of the POE chain. This demonstrated that the solvophilicity of the surfactants comes from POE chain. Thus, the cloud point decreased with increase of salt concentration. Surfactants D and E were the only ones that showed cloud point temperatures above the average temperature of oil wells (~70°C), even at high concentrations of salt, and surfactant E was most suitable for enhanced oil recovery operations.

Lyotropic Liquid Crystal Formed in Oleyl Polyoxyethylene Solutions by Adding Different Additives: NaDC, Tween 80, Alkyl Esters

Lyotropic liquid crystalline of oleylpolyoxyethylene(20)(AEO20)/oil/water system was investigated at 25°C. The phase behavior, microstructure, and rheological properties of liquid crystalline were investigated by rheological techniques and polarizingoptical microscopy in the presence of various additives including Tween 80, sodium deoxycholate (NaDC), isoamylacetate, butyl acetate, isopropyl myristate. Diagrams show that cubic phase transforms to hexagonal phase when a shorter chain length oil is applied or NaDC or Tween 80 is added to the system.Flow experiments indicate the shear-thinning properties and a plastic behavior. The turning points of flow curves of the system AEO20 and system AEO20/NaDC were found. The dynamic modulus increase with increase in water content however the tendency is weaken by adding NaDC. Frequency dependence of experimental G ′ and G ′ were fitted using the multiple Maxwell model the cubic LLCs described by three relaxation times while hexagonal LLCs described by 5–8 elements. When AEO20 mixes with Tween 80, the hexagonal have a monotonic decrease distribution of relaxation times without valleys.

Simple Method for the Melt Extrusion of a Cellulose Nanocrystal Reinforced Hydrophobic Polymer.

The rheological properties of a dispersion of cellulose nanocrystals (CNCs) in an aqueous solution of polyoxyethylene (PEO) have been investigated. A peculiar behavior is reported. Upon adding CNC, the viscosity of the suspension first decreases and then increases. Adsorption of PEO chains on the surface of the nanoparticles has been suspected. Freeze-drying of this PEO-adsorbed CNC dispersion was performed, and the ensuing lyophilizate was extruded with low density polyethylene. Compared to neat CNC-based nanocomposites, both improved dispersibility and thermal stability were observed. This simple and physical method constitutes an approach of choice for the melt processing of CNC-based nanocomposites with a hydrophobic polymeric matrix applicable at the industrial scale.

Structural Changes in PEO–PPO–PEO Gels Induced by Methylparaben and Dexamethasone Observed Using Time-Resolved SAXS

Aqueous solutions of polyoxyethylene–polyoxypropylene–polyoxyethylene (PEO–PPO–PEO) triblock copolymers (commercially available as Pluronic surfactants) micellize and structurally arrange into cubic quasicrystalline lattices as their temperature is raised. This structural evolution is seen macroscopically as a gelation, and the presence of these ordered phases can be controlled through both polymer concentration and temperature. The presence of added solutes within the dispersions can also affect the onset and kinetics of structure formation. Here we investigate the structures formed in Pluronic F127 solutions ranging from 20 to 30% with two pharmaceutical additives [methylparaben (MP) and dexamethasone (DX)] using small-angle X-ray scattering (SAXS). We observe both the progressive evolution and breakdown of these structures as the temperature is increased from 0 to 80 °C. Additionally, we conducted time-resolved SAXS measurements to elucidate the kinetics of the structural evolution. On the basis of the evolution of scattering peaks as the samples were being heated, we suggest that added MP changes the nucleation behavior of fcc phases within the sample from a heterogeneous process to a more homogeneous distribution of nucleated species. MP and DX also stabilize the micelle lattices, allowing them to persevere at higher temperatures. We observed the unusual result that the presence of DX caused the primary peaks of the structure factor to be suppressed, while preserving the higher order peaks. The primary peaks reappeared at the highest temperatures tested.

Coalescence of Bubbles and Stability of Foams in Brij Surfactant Systems

This work presents coalescence of air bubbles and stability of foams in aqueous solutions of polyoxyethylene (4) lauryl ether (Brij 30), polyoxyethylene (23) lauryl ether (Brij 35), and polyoxyethylene (20) oleyl ether (Brij 98). Adsorption of these surfactants at the air−water interface was also studied. The surface tension profiles were fitted by the Szyskowski equation. It was found that the surface tensions at the critical micelle concentrations of these surfactants followed the sequence Brij 35 > Brij 98 > Brij 30. The air bubbles were most stable to coalescence in Brij 35 solution and least stable in Brij 30 solution. Coalescence in Brij 35 solution was hindered beyond a certain concentration of the surfactant. Stochastic distributions of coalescence time were observed in all surfactant systems. These distributions were fitted well by the stochastic model. Seven film-drainage models were used to predict the coalescence time. However, their predictions did not agree well with the mean values of the coalescence time distributions. Stability of foams was analyzed by the Ross−Miles test. The initial and residual foam heights were measured at each surfactant concentration. The foam heights followed the trends that are expected from the coalescence times of the bubbles.

Using Electrocapillarity to Measure the Zeta Potential of a Planar Hydrophobic Surface in Contact with Water and Nonionic Surfactant Solutions

A method is introduced for determining the zeta potential of planar surfaces by combining electroosmosis and capillarity. In this method, an electric field is applied across the channel, which is filled with aqueous solution seeded with fluorescent tracer particles. Some excess liquid is applied on both ends of the channel, which bulges out and modulates the capillary force across the channel by adjusting its curvature. While the velocity profile in the channel approaches steady state, a balance of the electroosmotic stress and Laplace pressure difference is achieved across the channel. However, as soon as the electric field is turned off, a Poiseuille flow develops in the channel due to the difference in the curvatures of the liquid bulges. We show that the measurement of the centerline velocity of the liquid inside the channel is enough to deduce the zeta potential of the surface. Utilizing this technique, the zeta potential of a hydrophobic glass surface (silanized by n-hexadecyltrichlorosilane, HC-16) has been measured to be -52.2 +/- 7.7 mV in distilled deionized water, which is in close agreement with the literature values. This technique has also been used to estimate the zeta potential of the HC-16 surface (zeta w(HC-16)), in the presence of the aqueous solutions of polyoxyethylene (23) lauryl ether (Brij 35). The zeta potential here at first becomes more negative than that in pure water, it stays flat for a while, and then it continues to become less negative as the concentration of the surfactant increases above the critical micelle concentration (CMC). This effect, where changes take place beyond the CMC but not below it, leads to a complementary Gibbs plot, where all the changes occur below the CMC but not above it. It is conjectured that the scavenging of hydroxyl ions by the Brij 35 micelles may be responsible for the observed effect.

Aggregation Behavior of Polyoxyethylene (20) Sorbitan Monolaurate (Tween 20) in Imidazolium Based Ionic Liquids

Surface tension measurements were carried out for the solutions of polyoxyethylene (20) sorbitan monolaurate (Tween 20) in 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4) and hexafluorophosphate (bmimPF 6) at various temperatures. Two transition points were found in the surface tension-concentration curves at each temperature. The freeze-fracture transmission electron microscopy revealed that two kinds of particles with different sizes are formed at the concentrations of each transition point. Thus, the surfactant concentrations of the two transition points are regarded as critical aggregation concentrations, CAC 1 and CAC 2. From the CAC values and their temperature dependence, we estimated the thermodynamic parameters of the aggregate formation, Delta G agg (0), Delta H agg (0), and Delta S agg (0). The thermodynamic parameters related to CAC 1 are almost independent of temperature. On the other hand, as for the aggregate formation at CAC 2, a positiveDelta S agg (0) contributes to a negative Delta G agg (0) at low temperature, while a negative Delta H agg (0) contributes to a negative Delta G agg (0) at high temperature. The behavior of the thermodynamic parameters as a function of temperature, combined with the variation of (1)H NMR chemical shifts of the bmim (+) protons as a function of the surfactant concentration, demonstrated that the aggregates formed at CAC 1 are nanodroplets of Tween 20 segregated from the solution phase, while those formed at CAC 2 are similar to the usual surfactant micelles formed in aqueous solution.

An automated measurement setup for studying the dependences of the thermal conductivity and rheological characteristics of non-Newtonian fluids on the shear rate

An experimental setup designed for studying the rheological characteristics and thermal conductivity of liquid materials is described. The presented measurement and experimental-data-processing technique allows determination of the thermal conductivity of liquids as a function of the shear rate with allowance for the heat released in the studied material layer due to dissipation of the mechanical energy during a shearing motion and helps to find the consistence factor and the flow index for liquids that obey the power rheological law. The results of experiments on the determination of the thermal conductivity as a function of the shear rate of a 10% aqueous solution of polyoxyethylene and synthetic caoutchouc doped with nanostructural elements (carbon nanotubes and nanofibers) at different temperatures are presented. The thermal-conductivity measurement error is ≤10%, while the measurement errors for the consistence factor and the flow index are <7%.

Cloud point phenomena for POE-type nonionic surfactants in a model room temperature ionic liquid

The cloud point phenomenon has been investigated for the solutions of polyoxyethylene (POE)-type nonionic surfactants (C 12E 5, C 12E 6, C 12E 7, C 10E 6, and C 14E 6) in 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4), a typical room temperature ionic liquid (RTIL). The cloud point, T c , increases with the elongation of the POE chain, while decreases with the increase in the hydrocarbon chain length. This demonstrates that the solvophilicity/solvophobicity of the surfactants in RTIL comes from POE chain/hydrocarbon chain. When compared with an aqueous system, the chain length dependence of T c is larger for the RTIL system regarding both POE and hydrocarbon chains; in particular, hydrocarbon chain length affects T c much more strongly in the RTIL system than in equivalent aqueous systems. In a similar fashion to the much-studied aqueous systems, the micellar growth is also observed in this RTIL solvent as the temperature approaches T c . The cloud point curves have been analyzed using a Flory–Huggins-type model based on phase separation in polymer solutions.

Percutaneous Absorption of Polycyclic Aromatic Compounds from Bitumen Fume Condensate

Bitumen fume condensate was obtained from the headspace vapors of a bitumen storage tank containing a lightly oxidized paving-bitumen for the purpose of developing an in vitro procedure to estimate the percutaneous absorption, through human skin, of the very low levels of polycyclic aromatic compounds found in the condensate. The Fraunhofer Institute of Toxicology and Medicine provided the fume condensate and analyses of the individual polycyclics present. Heritage Research Group provided analyses of total 3–6 ring polycyclics. Sections of human back skin were sliced with a dermatome to a thickness of ∼ 250 μ m, and 1-inch circular pieces were mounted in 6 Franz diffusion cells. Tissue integrity was assured by electrical resistance measurement. Neat condensate was applied to the stratum corneum at “infinite dose” (200 μ l) while the dermis was in direct contact with a receptor fluid consisting of an aqueous solution of polyoxyethylene 20 oleyl ether. Receptor fluids were sampled at 12 intervals over 48 hours, and analyzed by an HPLC system equipped with a variable wavelength detector and a fluorescence detector connected in series. The UV detector was generally operated at 254 nm, and the fluorescence detector at ex360nm/em400nm, 18 nm bandpass. The mobile phase was a 60–100% acetonitrile/water gradient. Penetration rates of anthracene, fluoranthene-pyrene, and total 3–6 ring polycyclic aromatic compounds (PAC) were measured. The neat condensate was 32.7 μ g/g anthracene, 7.4 μ g/g fluoranthene, 7.3 μ g/g pyrene, and 1.8 mg/g total 3–6 ring PAC. The rates of dermal penetration (ng/cm2/hr ± SD) were: anthracene 6.5 ± 0.9; fluoranthene-pyrene 1.8 ± 0.3; and 3–6 ring PAC 120 ± 30. Percentages of applied dose absorbed were: anthracene 5.3%, fluoranthene-pyrene 3.3%, and 3–6 ring PAC 1.8%. The apparent permeability coefficient Kp (Kp = flux rate/applied concentration) for anthracene was 2 × 10− 4 cm/hr. These results demonstrate that penetration of PAC, at the low concentrations found in bitumen fume condensates, can be measured by an appropriately designed in vitro method. Rates of PAC percutaneous absorption will be further evaluated in the future with other fume condensates obtained from several different straight run paving asphalts.

Fluorometric sensing of alkali metal and alkaline earth metal cations by novel photosensitive monoazacryptand derivatives in aqueous micellar solutions

Novel monoazacryptand-type fluorescent chemosensors, (derived from an 18-crown-6) and (derived from a 15-crown-5) both with a pyrene ring as their photoresponsive moiety, were synthesized. Their fluorescence properties for alkali metal and alkaline earth metal cations in water were then examined. The detection of metal cations was accomplished by a change in the fluorescence intensity of the host compounds, based on a photoinduced electron transfer (PET) mechanism. In aqueous solution, showed little fluorescence upon the addition of Ba2+ because of the very weak complexation with Ba2+, but the presence of micelles of polyoxyethylene(10) isooctylphenyl ether (Triton X-100) enabled to show highly sensitive and selective Ba2+ detection among alkali metal and alkaline earth metal cations. With respect to the selective fluorescent detection of important metal cations (Na+, K+, Mg2+, Ca2+) relevant to living organisms, was found to detect K+ with high selectivity in aqueous micellar solutions of polyoxyethylene(20) sorbitan monostearate (Tween-60). The selectivity for metal cations was mainly dependent on the goodness of fit of the host cavity and the metal cation size. In the presence of anionic surfactants, detected alkaline earth metal cations more effectively than alkali metal cations.

Study of the thermal stability of glucose oxidase in the presence of water‐soluble polymers

AbstractThe thermal stability of glucose oxidase (GOD) in solutions containing water‐soluble hydrolyzed polyacrylonitrile (HPAN) and polyoxyethylene (POE) was studied as a function of time and temperature between 28 and 60°C. The results were compared with the thermal stability of GOD in solutions without polymers. The polymers studied were found to increase the enzyme thermal stability. The influence of the concentration of the water‐soluble polymers on enzyme thermal stability was also studied. The best protection effect on enzyme thermal stability had 3 wt % solution of HPAN and 1 wt % solution of polyoxyethylene. Solutions with higher concentrations led to a quick deactivation of the enzyme. It was proved that the effect of 3 wt % HPAN solution was stronger than the effect of 1 wt % POE (59.0 versus 52.0%). The thermal transition of the enzyme was studied in both the presence and the absence of HPAN by DSC. The melting temperature of GOD in the presence of HPAN was shifted to an 11°C higher value. This sustained the supposition that HPAN increases the thermostability of GOD. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1393–1397, 2003

Thin wetting films from aqueous solutions of a polyoxyethylene–polyoxypropylene block copolymer on silicon carbide surface

Thin wetting films from aqueous solutions of polyoxyethylene–polyoxypropylene ABA-block copolymer+NaCl in different concentrations on silicon carbide substrate have been studied. The polymer adsorption at the silicon carbide/aqueous solution interface has been studied using the spectrophotometric method, based on the colored polymer–iodine complex. The area per molecule, the conformation of the adsorbed molecules and the thickness of the adsorption layer at the solid/liquid interface were determined. The three-layer model of the structure of thin liquid films on the flat SiC surface has been used for calculation of the film thickness from the data obtained by the microinterferometric method. The dependence of the film thickness on time has been determined. The influence of the electrolyte concentration on the equilibrium film thickness has been studied. It was found that for NaCl concentrations higher than 3×10 −2 M the film thickness remained constant, i.e. the electrostatic disjoining pressure was fully suppressed. The disjoining pressure/thickness-isotherm has been obtained experimentally using the dynamic method. It has been interpreted by the superposition of a negative van der Waals component and a positive steric component of the disjoining pressure.

Kinetic study of the reaction *[Ru(bpy) 3] 2++S 2O 82− in solutions of Brij-35 at premicellar and micellar concentrations

The title reaction was studied in solutions of polyoxyethylene(23) lauryl ether (Brij-35) at premicellar and micellar concentrations. The reaction rate goes through a maximum, which appears at a concentration close to the critical micellar concentration (cmc). The results can be rationalized by an extension of previous models on premicellar and micellar effects on the kinetics of reactions. This model can explain similar results from other groups.