Cloud Point Studies of Tween and Glycol in the Presence of Salts

This article deals with the cloud point studies of ethoxylated sorbitan ester, Tween in the presence of glycols, and salts. Cloud point temperature of Tween 20 (5 mol dm^?3) and Tween 80 (1 mol dm^?3) has been determined in the presence of various salts in addition to glycols. The glycols chosen for these studies were triethylene glycol (TEG), and ethylene glycol mono butylether (EGMBE). At concentration below 0.02 M these salts have no significant effect on cloud point temperature in all cases. The cloud point temperature of Tween+TEG and Tween+EGMBE found to decrease in the presence of sodium chloride (NaCl) and potassium chloride (KCl). The cloud point temperature of Tween 20 + TEG and Tween 20 + EGMBE found to increase in the presence of urea and nicotinamide. The change in cloud point was found to be more in case of nicotinamide as compare to urea. The influence of an additive on the cloud point depends on how it affects the intermicellar interactions. An effort has been made to understand the interaction between solvent and additives leading to a change in solubility of Tween.     

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.     

Estimation of degree of counterion binding and related parameters of monomeric and dimeric cationic surfactants from cloud point measurements by using triblock polymer as probe

The cloud point (C _P) measurements of aqueous solutions of a triblock polymer (TBP) [(PEO)_2.5(PPO)₃₁(PEO)_2.5], in the presence of varying amounts of cationic surfactants (monomeric and dimeric alkylammoniumbromides) covering premicellar to postmicellar regions, have been carried out. A plot of C _P vs surfactant concentration allowed us to evaluate apparent critical micelle concentration (cmc*), which has been found to decrease with an increase in the amount of salt. The cmc* values thus obtained in the absence and presence of salt allowed us to evaluate counterion binding (β) by using the Corrin–Harkins method. β values have been further used to evaluate the thermodynamic parameters of these ionic surfactants. The results suggest that the β values evaluated using this method, especially at low [TBP], are in good agreement with those already reported in the literature.     

INFLUENCE OF ELECTRON-WITHDRAWING SUBSTITUENTS IN THE OXAPHOSPHOLE RING ON THE AXIAL CONFORMATIONAL TRANSMISSION IN Pv COMPOUNDS

Abstract

A MNDO and 300-MHz ¹H NMR study of some trigonal-bipyramidal (TBP) five-coördinated phosphorus (P^v) compounds is reported. It is shown by the MNDO calculations that, in the oxaphosphole P^v TBP compounds 5a-c, the electron distribution in the axial bonds of the TBP is affected by the electronegativity of the substituent at C₄ of the oxaphosphole ring. With increasing electronegativity of the substituent at C₄, the electron density on the axial exocyclic oxygen atom O₁ decreases whereas the electron density on the axial endocyclic atom O₁ increases. This is supported by a ¹H NMR conformational analysis of the C₁[sbnd]C₂ bond of the oxaphosphole P^v TBP compounds 6–11. The gauche(-) rotamer fraction (O¹ and O¹ trans situated) of these compounds, which is correlated to the electron density on O₁, is reduced to 30% as compared to the absolute axial g^?rotamer fraction (59%) of the dioxaphosphole P^v TBP compound 13, most likely because of the presence of the carbonyl group at C₄ of the oxaphosphole ring. So, both the ¹H NMR and MNDO study show that electron withdrawing substituents on the oxaphosphole ring of P^v TBP compounds reverse the electron transfer in the axial P[sbnd]O bonds of the TBP (as compared to dioxaphosphole compounds), from exocyclic O₁ towards endocyclic O₁.     

Effect of Association of Bromophenol Blue with Tween Surfactants on Its Acid-Base Equilibria at High pH

The acid base equilibria of the sulfonephthalein dye bromophenol blue (BPB) in aqueous nonionic micellar solutions of Tween 20, Tween 40, Tween 60, and Tween 80 have been investigated spectroscopically using a partition equilibrium method. A visible red shift in the absorbance of the basic form of the dye with increase in surfactant concentration was observed at and above pH 6.98. This has been attributed to the stabilization of the acid form of the dye by the POE groups on the head of the surfactant monomers. Such stabilization effect was found to decreases with decrease in the number of carbon atom in the hydrophobic tail and with the increase in the hydrophile-lipophile balance (HLB) of the surfactant molecule. The equilibrium constant of the partition of the dyes between micellar and aqueous pseudophases (K_ass) was found to increase with the surfactants in the order Tween 80 < Tween 60 < Tween 40 < Tween 20. The pK_a2 of the dyes were predicted and found to be in good agreement with the experimental values.     

A Potentiometric Study of the Briggs–Rauscher Oscillatory Reaction in a Solution of Nonionic Surfactants and tert‐Butanol

The concentration effect of nonionic surfactants (Triton X‐100, Brij 30, Brij 58, Tween 20, and Tween 80) and tert‐butanol was investigated on the Briggs–Rauscher oscillatory reaction in a stirred batch reactor at 25 ± 0.1°C in both the absence and presence of nonionic surfactant and tert‐butanol as well. The addition of Triton X‐100, Brij 58, and Tween 20 influenced the oscillatory parameters in a similar fashion: a decrease of the induction period until its disappearance, an increase of the oscillation period, an increase of the oscillation amplitude, an increase of the duration of the oscillation, and a gradual increase of the oscillation numbers. The addition of Brij 30 has no significant effect on the oscillation parameters of the Briggs‐Rauscher oscillatory reaction. The effect of tert‐butanol on the Briggs–Rauscher oscillatory reaction is very similar to the effect of Brij 58; however, we were unable to observe the disappearance of the induction period on the studied concentration range. The addition of Tween 80 to the reaction mixture has a similar effect as the addition of Triton X‐100, Brij 58, or Tween 20, except for the induction period, which in the case of Tween 80, it becomes larger. The observed effects are explained in terms of micellar catalysis or inhibition, that is, in a different extent of individual reactants of solubilization.     

Association of hydrophilic derivatives of chlorophyll <Emphasis Type="Italic">a</Emphasis> in ethanol–water and ethanol–water–solubilizer systems

Electronic absorption spectroscopy and fluorescence spectroscopy were used to study conditions for the formation of associates of amphiphilic phorbins and chlorins in an ethanol–water system. The conditions and degree of disaggregation in the presence of solubilizing additives of nonionic surfactants (Tween 80) and biocompatible polymers (polyethylene glycol and polyvinylpyrrolidone) were also investigated. The propensity of the macroheterocycles based on chlorophyll a to association in water-alcoholic solutions decreases on going from covalently bound dimeric structures to monomeric ones, on going from phorbins to chlorins and on accumulating hydrophilic glycol or positively charged alkylammonium fragments in the molecule. Among the considered solubilizers, the nonionic surfactant Tween 80 emerged as the most efficient means for destroying chlorin associates in water–alcohol solutions with a high content of water.     

Effect of adding glycols to the micellar properties of Tween: small-angle neutron scattering and turbidity measurements

Small-angle neutron scattering (SANS) and turbidity measurements have been carried out on the nonionic surfactants Tween 20 and Tween 80, in the presence of diethyleneglycol (DEG), triethyleneglycol (TEG), ethylene glycol monoethyl ether (EGMEE), and ethyleneglycol mono butyl ether (EGMBE). SANS measurements show that the shapes of the Tween 20 and Tween 80 micelles are oblate ellipsoidal, which do not change predominantly in the presence of DEG and TEG. However, the presence of EGMBE and EGMEE reduces the aggregation number of Tween. This has been attributed to the solubilization of EGMBE and EGMEE in the Tween micelles, providing them with additional hydrophobicity.     

Influence of various series of additives on the clouding behavior of aqueous solutions of triblock copolymers

The cloud point (CP) studies on aqueous solutions of two ethylene oxide-propylene oxide triblock copolymers (EO)_2.5(PO)₃₁(EO)_2.5 and (EO)₁₃(PO)₃₀(EO)₁₃ with varying number of ethylene oxide (EO) units were carried out in the presence of series of additives, such as alkali, acids, ionic surfactants, alcohols, salts, and hydrotropes. The results of this study show that sodium hydroxide decreases the CP of the two copolymers. Acids increase the CP in the order hydrochloric acid > acetic acid > formic acid for both the triblock copolymers. Hydrotropes increase the CP, whereas salts decrease or increase the CP based on their salting-out/salting-in nature. Alcohols, which are polar organic additives, affect the CP of the two copolymers differently. The change in the CP of the triblock copolymers depends upon the structure and concentration of the additives and on the number of EO units of the two triblock copolymers.     

HEXADECYLTRIMETHYLAMMONIUM BROMIDE + TETRADECYLTRIMETHYL-AMMONIUM BROMIDE MIXED MICELLES IN AQUEOUS GLYCOL OLIGOMERS

The conductances of hexadecyltrimethylammonium bromide (HTAB) + tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of HTAB (α_HTAB) were measured in pure water as well as in the presence of various aqueous ethylene glycol oligomers containing 5, 10 and 20 wt% of each additive in their respective binary mixtures at 30°C. From the conductivity data, the critical micellar concentration (cmc), degree of counter ion association (χ) and the standard free energy of transfer of the surfactant hydrocarbon chain from the medium to the micelle (ΔG^O _HP ) for HTAB and TTAB were computed. From the conductivity data of mixed surfactants systems, apart from cmc and χ, the regular solution theory parameters were also computed in order to explore the non-ideality in the mixed micelle formation in the presence of additives. The micellar parameters of both kind of surfactants and their mixtures show a significant dependence on the amount as well as on the number of repeating units of glycol oligomers. However, the non-ideality of mixed micelle formation remains unaffected in the presence of additives. These results have been explained on the basis of the medium effects of aqueous additive and it has been concluded that there are no significant interactions of glycol oligomers with the micelles of single and mixed surfactants.     

Analysis of some commercial polysorbate formulations using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Analyses of polysorbate formulations (Tween 20, Tween 40, Tween 60, and Tween 80) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) reveal a complex mixture of oligomers that include polyethylene glycols, polyethylene glycol esters, isosorbide polyethoxylates, sorbitan polyethoxylates, polysorbate monoesters, polysorbate diesters, and sorbitol polyethoxylate esters. The MALDI-TOF mass spectra for these formulations show the presence of sodiated molecules in which the major signals are attributed to the presence of polyethylene glycols, isosorbide polyethoxylates, and sorbitan polyethoxylates. Additionally, the complexity of the spectra was correlated to the constituent fatty acid moieties in the polysorbate formulations. Thus Tween 20 showed the presence of polysorbate monolaurates, polysorbate monomyristates, and polysorbate monopalmitates. Tween 40 contained polysorbate mono- and dipalmitates. Tween 60 contained polysorbate monopalmitates and polysorbate monostearates. For the Tween 80, mass assignment for polysorbate monooleates and polysorbate dioleates was equivocal, because both of these oligomeric series have the same molecular weight as the sorbitan polyethoxylates, and thus the Tween 80 MALDI-TOF spectrum appeared to be the least complicated of the four commercial polysorbate formulations.     

Effect of the composition ratio of copolymerized poly(carbonate) glycol on the microphase‐separated structures and mechanical properties of polyurethane elastomers

Randomly copolymerized poly(carbonate) glycols were employed as starting materials for the synthesis of polyurethane elastomers (PUEs). The poly(carbonate) glycols had hexamethylene (C₆) and tetramethylene (C₄) units between carbonate groups in various composition ratios (C₄/C₆ = 0/100, 50/50, 70/30, and 90/10), and the number‐average molecular weights of these poly(carbonate) glycols were 1000 and 2000. The PUEs were synthesized with these poly(carbonate) glycols, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol by a prepolymer method. Differential scanning calorimetry measurements revealed that the difference between the glass‐transition temperature of the soft segment in the PUEs and the glass‐transition temperature of the original glycol polymer decreased and the melting point of the hard‐segment domain increased with an increasing C₄ composition ratio. The microphase separation of the poly(carbonate) glycol‐based PUEs likely became stronger with an increasing C₄ composition ratio. Young's modulus of these PUEs increased with an increasing C₄ composition ratio. This was due to increases in the degree of microphase separation and stiffness of the soft segment with an increase in the C₄ composition ratio. The molecular weight of poly(carbonate) glycol also influenced the microphase‐separated structure and mechanical properties of the PUEs. The addition of different methylene chain units to poly(carbonate) glycol was quite effective in controlling the microphase‐separated structure and mechanical properties of the PUEs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4448–4458, 2004     

The synergistic effect of polysorbate 80 upon the toxicity of tri-n-butyltin chloride

Polysorbate 80 (Tween 80) was used as an emulsifying agent for administering tri-n-butyltin chloride (TBTCl) to rats below, at and above the LD₅₀ for the compound. Tween 80 greatly enhanced the toxicity of the organotin compound. The LD₅₀ in the presence of Tween 80 (16% of the emulsion) is less than half of the LD₅₀ when the TBTCl was administered in corn oil.     

Calorimetric relaxation and glass transition in poly(propylene glycols) and its monomer

The glass transition temperature T_g of propylene glycol (PG) and poly(propylene glycols) (PPGs) of molecular weight up to 4000 has been measured by differential scanning calorimetry, and the activation energy and change in heat capacity ΔC_p have been determined in the glass transition range. The activation energy increases with an increase in the molecular weight of the polymer, and ΔC_p measured at a fixed heating rate decreases. The increase in T_g with molecular weight is remarkably more rapid for poly(propylene glycols) than for other polymers, and a limiting value of T_g is reached for a chain containing 20 monomer units. These results are discussed in terms of the Fox-Flory and the entropy theories. The calorimetric relaxation times are comparable with the extrapolated dielectric relaxation times. The initial increase of ΔC_p from PG to PPG 200 is attributed to the decrease of H-bonding sites from 12 in 3 monomers to 4 on polymerization to PPG 200 and further decrease with increase in molecular weight to an increasingly large amplitude of the β-process at T < T_g.     

Investigation on Adsorption Dynamics of Protein/Tween‐20 Mixture at the Surface of Solution by Surface Pressure Measurement

The dynamic surface tension (γ_t) and apparent diffusion coefficient (D) of nonionic surfactant Tween‐20 in the presence and absence of bovine serum albumin (BSA) have been investigated via the measurements of surface pressure (π) at different time (t). The curves of γ_t～t are obtained from π～t isotherms. Results show that the γ_t～t relationships of Tween‐20 solution with or without BSA accord with the Ward‐Tordai equation in the region of initial adsorption. D value obtained from the γ_t～t^1/2 curves shows that the diffusion of Tween‐20 slows down with the increase of the concentration of Tween‐20 (c _Tween‐20). And D value of Tween‐20 in the presence of BSA is almost the same as that of the system without BSA when c _Tween‐20 is constant, suggesting that the interaction between Tween‐20 and BSA is weak.     

Studies of Photon Correlation Spectroscopy of the Microemulsion of H2O/Tween 80/Benzene Derivative

The microemulsion of the H₂O/Tween 80/benzene derivative (C₆H₆, CH₃C₆H₅, NO₂C₆H₅ and NH₂C₆H₅) was investigated by the technique of Photon correlation spectroscopy. Autocorrelation data were measured at 90 scattering angle and were analyzed by using a quadratic fit and linear fit. The quadratic fit was found to describe all Properties better than the linear fit, and thus the linear fit was limited to the region of very short sampling time. When the amount of benzene derivative added to the sample solution was lower than V_max, the Z-average mean radius, <r>_z, and the polydispersit Y, μ2/Γ², increased as the amount of benzene derivative was increased. When the amount of benzene derivative was larger than V_max, the aqueous and organic phases separated and the <r> z, and μ₂/Γ² of all phases remained constant. Emulsification did not occur in the organic phase of the H₂O/Tween 80/aniline system. When we adjusted the Tween 80 concentration, it was found that <r>z and μ₂/Γ² decreased as the Tween 80 concentration increased.     

Dilational Rheological Properties of Non-Ionic Surfactants at the Water–Decane Interface: Effect of Unsaturated Hydrophobic Group

The interfacial tensions and dilational properties of adsorbed films of two non-ionic surfactants with different hydrophobic groups, polyoxy-ethylene sorbitan stearate (Tween 60) and polyoxy-ethylene sorbitan monooleate (Tween 80), at the water–decane interface have been investigated by the drop-shape analysis method. The effects of dilational frequency and bulk concentration on the interfacial properties were expounded. The influence of low temperature on the interfacial tensions and dilational properties have also been researched. The experiment results show that the interfacial activity of Tween 80 is rather large compared with Tween 60. The minimum area per molecule at the water–decane interface (A_min) value of Tween 80 is little large than that of Tween 60, which is due to the steric effect of unsaturated double bond in Tween 80 molecule. The dilational data show that the ethylene oxide groups of non-ionic surfactant form a stable sub-layer, which results in the increase of modulus and the decrease of phase angle for both Tween 60 and Tween 80 than those of common ionic surfactants. Moreover, the unsaturated hydrophobic group of Tween 80 is much flexible, which is easily crosslinked and entangled. Therefore, dilational modulus of Tween 80 is higher and phase angle is lower than that of Tween 60. Low temperature decreases the flexibility of unsaturated hydrophobic group and lessens the influence on the interaction of saturated hydrophobic group. Saturated surfactant molecules of Tween 60 almost lose temperature response.     

Solubilization of fullerene C60 in micellar solutions of different solubilizers

Fullerene (C₆₀), the third carbon allotrope, is a classical engineered material with the potential application in biomedicine. However, extremely high hydrophobicity of fullerene hampers its direct biomedical evaluation and application. In this work, we investigated the solubilization of fullerene using 9 different solubility enhancers: Tween 20, Tween 60, Tween 80, Triton X-100, PVP, polyoxyethylene (10) lauryl ether, n-dodecyl trimethylammonium chloride, myristyl trimethylammonium bromide and sodium dodecyl sulphate and evaluated its antioxidant activity in biorelevant media. The presence of C₆₀ entrapped in surfactant micelles was confirmed by UV/VIS spectrometry. The efficacy of each modifier was evaluated by chemometric analysis using experimental data for investigating the relationship between solubilization and particle size distribution. Hierarchical clustering and principal component analysis was applied and showed that non-ionic surfactants provide better solubilization efficacy (>85%). A correlation was established (r = 0.975) between the degree of solubilization and the surfactant structure. This correlation may be used for prediction of C₆₀ solubilization with non-tested solubility modifiers. Since the main potential biomedical applications of fullerene are based on its free radical quenching ability, we tested the antioxidant potential of fullerene micellar solutions. Lipid peroxidation tests showed that the micellar solutions of fullerene with Triton and polyoxyethylene lauryl ether kept high radical scavenging activity, comparable to that of aqueous suspension of fullerene and BHT. The results of this work provide a platform for further solubilization and testing of pristine fullerene and its hydrophobic derivatives in a biological benign environment.     

Kinetic Effects in non Ionic Micellar Solutions

The elimination reaction between 2-(p-nitrophenyl)ethyl bromide and OH^- ions was studied in nonionic aqueous micellar solutions of two esters of long chain fatty acids and sorbitan polyethylene glycol, Tween 20 (monolaurate) and Tween 80 (monooleate). The equilibrium binding constants of the 2-(p-nitrophenyl)ethyl bromide molecules to the nonionic micellar aggregates were obtained by spectroscopic measurements. The experimental kinetic data were quantitatively rationalized by the treatment of first-order reactions based on the pseudophase model. Results from this work and from previous studies show that, whereas the presence of cationic and sulfobetaine micelles accelerates the reaction, the presence of nonionic micelles inhibits the reaction.     

Investigation of PEG 6000/Tween 80/Span 80/H<Subscript>2</Subscript>O niosome microstructure

A stable niosome is prepared from Poly(ethylene glycol) [PEG] 6000/Tween 80/Span 80/H₂O lamellar liquid crystal. The niosome structures and properties are studied by the methods of negative-staining transmission electron microscopy and small angle X-ray diffraction. A new calculating method is first put forward to obtain the microstructure and layer number of the niosome membrane. The membrane thickness and layer number of the niosome are 8–22 nm and 1–3.5 in PEG 6000/Tween 80/Span 80/H₂O system.