TX-100 Micelles Research Articles

Coadsorption of alkylphenols and nonionic surfactants onto kaolinite

The influence of a nonionic surfactant on the adsorption behaviour of alkylphenols onto kaolinite is studied by determining their adsorption isotherms separately or in the presence of various concentrations of the nonionic surfactant. When alone, alkylphenols are adsorbed with a mechanism close to that of surfactants. If the nonionic surfactant TX100 is added in the medium, the adsorbing properties are modified according to the alkyl chain length. The longer the alkyl chain length of alkylphenol molecule, the weakest is the influence of TX100 surface aggregates on their adsorption behaviour. This unexpected behaviour, according to the relative hydrophobicity of the molecules, may be due in a part to the adsorbing properties of the alkylphenols that are able to self-aggregate at the kaolinite/water interface and in a part to the limited swelling capacity of the TX100 micelles or surface micelles. Partition coefficients between aqueous solution and surface aggregates are determined and compared with that calculated for bulk micelles.

UV–visible and fluorescence spectral study on a pH controlled transfer process of an amphiphilic porphyrin in nonionic micelle

5,15-di(4-hydroxyphenyl)-10,20-di(hexadecyloxyphenyl) porphyrin P was solubilized in nonionic polyoxyethylene(9.5) octylphenol (Triton X-100 or TX-100) micelle solutions. By means of analyzing the UV–visible and fluorescence spectra of the synthesized amphiphilic porphyrin P in different solvent environments, and the relationship between the solubilizing location of the porphyrins in TX-100 micelle and the microenvironment polarity, P is shown to involve in a transfer process for the porphyrin moiety from inner to the outer surface of TX-100 micelle as the pH is increased. The kinetic study of porphyrin incorporate with Cu(II) shows that metalation rate of porphyrin increases with the pH increasing, indicating that metalation rate could be controlled by changing pH.

Photophysical and light scattering studies on the aggregation behaviour of Triton X-100 in formamide—water mixed solvents

Micelle formation and structure of the non-ionic surfactant p-tert-octyl-phenoxy (9.5) polyethylene ether (Triton X-100) in mixed solvents consisting of water and formamide have been investigated. Changes in the critical micelle concentration of the surfactant upon the addition of formamide were examined by using the pyrene 1:3 ratio method. The observed increase in the critical micelle concentration was attributed to a rise in the solubility of the surfactant as the formamide content increased in the solvent system. Micelle structure parameters were obtained as a function of the co-solvent concentration by using combined static and dynamic light scattering measurements. It was found that the decrease in the micelle size, produced by the addition of formamide, is mainly due to a reduction in the mean aggregation number rather than to changes in the magnitude of the whole solvation of micelles. This fact was also supported by the observed trend in the partial specific volume of the TX-100 micelles, obtained by complementary density measurements. However, the postulated changes in the composition of the solvation layer of micelles were supported by the rise in both the surface area per head group and the cloud point of the surfactant. From the photophysical response of different fluorescent probes incorporated in the micellar phase, we obtained information on the changes in the microstructure of Triton X-100 micelles upon the addition of formamide. The pyrene 1:3 ratio index revealed an increasing micropolarity as the formamide content increases in the solvent system. On the other hand, studies based on both fluorescence polarization of coumarin 6 and intermolecular pyrene excimer formation have shown that the microviscosity of Triton X-100 decreases with the presence of co-solvent. These results were interpreted on the basis of considerable contact of the co-solvent with the inner region of the micelles.

Effect of surfactants on the thermodynamic properties of Methyl Orange dye in buffered solutions

The apparent thermodynamic parameters of ionisation and the association constants of the two forms of Methyl Orange were evaluated in the presence of different surfactants (TX‐100 as nonionic, CTAB as cationic and SDS as anionic). The enthalpy of ionisation of the dye in aqueous solution and at different surfactant concentrations is obtained from a novel thermochromic method and is found to decrease in aqueous medium in CTAB and TX‐100 micelles and to increase in the case of SDS micelles. The apparent ionisation constant of the dye is evaluated spectrophotometrically for each surfactant concentration and type. The apparent Gibbs free energy, entropy of ionisation and association constants are also calculated. The results are discussed in light of the stabilisation of the two forms of the dye in the micellar core of the different surfactants and their effect on properties of the bulk solution is examined.

Time-Resolved EPR Investigation of the Photo-initiated Intramolecular Antioxidant Reaction of Vitamin K−Vitamin E Linked Molecule

The models of vitamin K and vitamin E linked molecule, (1-(1,4-naphthoquinone-2-oxy)-6-(hydroxy-2,5,7,8-tetramethylchroman-2-carbonyloxy)-hexane), was synthesized as a model of vitamin K and vitamin E which coexist in biological membranes. The time-resolved EPR (TR-EPR) spectra of this molecule could be assigned to vitamin K and E radicals and showed that the excited triplet state of the vitamin K moiety was rapidly quenched by abstraction of hydrogen from the vitamin E moiety. The broad and emissive CIDEP spectra observed in ethanol suggested that the intramolecular interaction between vitamin K and vitamin E radicals was strong there. The relatively resolved spectra observed in a TX-100 micelle system, on the other hand, indicated that the interaction between these radicals was very weak. These results suggest that the vitamin K and E radicals existed around the water−oil interface of the micelle independently. The absence of a deuterium effect in our experiments showed that tunneling does not contribute significantly to the quenching reaction.

Effect of Surfactant Microenvironment on SOD-like Activity of Cu(II)-Salicylate Complex

Cu(II)-salicylate was synthesized and characterized by X-ray diffraction. The reaction mechanism of the Cu(II) complex with superoxide anion was studied by ESR spectroscopy, and its (superoxide dismutase) SOD-like activity was determined by a modified illumination method in phosphate buffer (pH = 7.8), micelle solutions and lamellar liquid crystals formed from surfactants CTAB and TX-100. X-ray diffraction indicated that the Cu(II) complex had a formula Cu2(Hsal)4EtOHH2O and a similar structure to the SOD active site. EPR spectra proved that the reaction mechanism of the Cu(II) complex catalyzing O 2 .- dismutation was the same as that of the proposed dismutation reaction catalyzed by SOD. Results obtained by the NBT method indicated that the Cu(II)-complex showed SOD-like activity, and the effect of microenvironment created by surfactants on its activity was same as on SOD activity. The order of the inhibition of NBT reduction by the Cu(II)-complex in different microenvironments was: in phosphate buffer (pH = 7.8) > in TX-100 micelle > in TX-100 liquid crystal, and in nonionic TX-100 organized assemblies > in cationic CTAB organized assemblies. These results were explained by the catalytic effect of micelles, and by the space restriction and high viscosity of organized assemblies of surfactants.

Effect of Microenvironment Created by Surfactant on Superoxide Dismutase Activity

The activity of SOD (superoxide dismutase) catalyzing dismutation of superoxide radical anion O2 − was studied by a modified NBT (nitroblue tetrazolium) method in aqueous solution, micellar solutions and lamellar liquid crystals (LLC) consisting of the surfactants CTAB and TX-100. The experiments showed that the inhibition by SOD of NBT reduction in organized assemblies of surfactants was weaker than in aqueous solution. The order of inhibition was as follows: in phosphate buffer (pH = 7.8) > in TX-100 micelle > in CTAB micelles > in TX-100 LLC > in CTAB LLC. The results were explained by decrease of α-helical content in SOD and difficulty in the transformation of SOD configurations in organized assemblies of surfactant, as well as by catalytic effects of micelles on NBT reduction.

Micellar aggregates of platinum(II) complexes containing porphyrins

The complex [Pt(Cy2dim)Me]4(TpyP)(CF3SO3)4 (1) (Cy2dim=dicyclohexyldiimine; TpyP=5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphine) has been synthesized and characterized with a number of spectroscopic techniques. The solubilization of 1 in anionic (sodium dodecyl sulfate, SDS) and neutral (Triton X-100, TX-100) aqueous surfactant solutions has revealed two different modes of interaction: (i) aggregation in the hydrophobic region of SDS micelles; and (ii) aggregation in the hydrophobic region with partial intercalation in the solvent accessible area of TX-100 micelles. In the case of SDS, the formation of premicellar aggregates has been evidenced by a surfactant concentration range two orders of magnitude lower than the critical micellar concentration (cmc). The metalated Mn(III)TpyP derivative of complex 1 exhibits a moderate peroxidase activity in agreement with the aggregation models proposed for the micellar solutions.

Spectral properties and structure of fluorescein and its alkyl derivatives in micelles

The absorption and fluorescence spectra, the fluorescence quantum yields and lifetimes of fluorescein and three series of alkylated fluorescein, namely, esters, ethers and esterethers of fluorescein in SDS, CTAB and TX-100 micelles, were investigated. The interactions between the dyes and micelles, and the existing structure forms of the dyes in micelles were also studied. All alkylated fluorescein could bind to the three micelles because of the hydrophobic interaction between their alkyl(s) and the hydrophobic region of the micelles, while the aqueous soluble fluorescein could not bind to SDS and TX-100 micelles. However, fluorescein could bind to the cationic CTAB micelles and existed mainly as dianion forms due to the electrostatic attraction. As a supplement to the hydrophobic interaction between the dyes and micelles, the electrostatic attraction enhanced the binding of esters and ethers of fluorescein to CTAB micelles and stabilized their anion forms. In SDS and TX-100 micelles, the esters of fluorescein existed mainly as neutral quinoid forms, while the ethers as neutral lactonic forms. As the alkylation of both the carboxyl and the hydroxyl, the esterethers of fluorescein could only exist as quinoid forms in all micelles. In each series, the hexadecylated fluorescein bound to micelles stronger than the butylated.

Interaction between Anionic Dye ECAB, Micelle of Triton X-100 in Aqueous Solution and Hemimicelie at Solid/Liquid Interface

Interaction between dye (ECAB), nonionic surfactant (TX-100) micelle in aqueous solution and TX-100 hemimicelie at solid (SiO2)/liquid interface has been investigated quantitatively. There are linear relationships between concentrations of free ECAB(Ca), ECAB bound with TX-100 micelles in solution(Cm) and ECAB bound with TX-100 hemimicelles at interface of solid/liquid(Chm). The slopes of the three straight lines are 0.32 for Chm∼Ca -1.32 for Cm∼Ca and -1.00 for (Cm+Chm∼Ca respectively. The linear relationships can be described by three linear equations as follows: Chm=0.32 (Ca−O.88×10−5),Cm.=4.0×10−5-l.33 Ca and Chm+Cm=3.742×l0−5-Ca,. It is inferred that the interaction between ECAB, TX-100 micelles and TX-100 hemimicelles is essentially partition of ECAB molecules in solution, TX-100 micelles and hemimicelles. The concentration of ECAB bound with TX-100 micelles well as electronic repulsion. Additionally, A quantitative method to determine adsorbance of surfactant TX-100 on silica gel by spectroscopy in coadsorption conditions of dye (ECAB) and TX-100 was proposed.

The effects of weak magnetic fields on radical recombination reactions in micelles

Purpose : To demonstrate the effects of weak magnetic fields (> ˜ 1 mT) on chemical reactions involving free radicals, in the context of possible effects of environmental electromagnetic radiation on biological systems. Materials and methods : Transient absorption, flash photolysis experiments have been performed to study the kinetics and yields of radical reactions. The triplet state of benzophenone has been used as a convenient source of radical pairs, whose identity is largely immaterial to the investigation of the so-called Low Field Effect. Hydrogen abstraction from surfactant molecules in micelles yields a pair of neutral radicals, one large and one small, in a region of restricted translational and rotational motion. Results : In alkyl sulphate and sulphonate micelles a weak field increases the concentration of free radicals that escape from the micelle to an extent that depends on the structure, dynamics and volume of the space in which the radical pairs are confined. The effect (up to 10%) is typically largest at 1-2 mT. Smaller effects are found for Brij and TX100 micelles. Conclusions : Low Field Effects depend strongly on the local environment of the radical pair. Larger effects than observed here might be expected for radicals formed from singlet (rather than triplet) precursors, as would be the case in biological reactions.

Interactions of Water-Insoluble Tetraphenylporphyrins with Micelles Probed by UV−Visible and NMR Spectroscopy,

For developing clinically useful porphyrin drugs, it is essential to characterize porphyrin−membrane interactions and to determine the factors that modulate such interactions. To this end, four uniquely p-phenyl-substituted tetraphenylporphyrins were synthesized. These water-insoluble, unsymmetrically substituted porphyrins were allowed to diffuse into aqueous micellar solutions formed by the surfactants tetradecyltrimethylammonium bromide (TTAB), sodium dodecyl sulfate (SDS), and poly(ethylene glycol)-p-t-octylphenol (TX-100). The abilities of the porphyrins to localize in these micelles were determined by UV−vis and NMR spectroscopy. The data show that the NO2−phenyl-substituted porphyrin did not diffuse into any of the micellar solutions. The COO--substituted porphyrin was solubilized in cationic TTAB and in nonionic TX-100 micellar solutions under neutral and basic conditions. The NH3+-substituted porphyrin incorporated in anionic SDS micelles at pH = 2 and in TX-100 micelles at pH 2 and 7. These resu...

Electrochemical and Optical Study of Carotenoids in TX100 Micelles: Electron Transfer and a Large Blue Shift

The first oxidation waves of 8‘-apo-β-caroten-8‘-al (I) and 8‘-apo-β-caroten-8‘-nitrile (II) in TX100 micelles are clearly observed in their cyclic voltammograms (CVs). The CV of β-carotene (III) in TX100 micelles shows that III is not oxidized. It is proposed that the hydrophobic barrier of the micelle is an important reason for the failure to oxidize III, which is totally located in the hydrophobic center of the micelle. The oxidation of I and II demonstrates that electrons can be transferred through the terminal groups over a distance of ca. 22 A. An unusually large blue band shift (100 nm, relative to that in CH2Cl2) is observed in the optical absorption spectrum of 7‘-apo-7‘,7‘-dicyano-β-carotene (IV) in TX100 micelles. This phenomenon is not observed in the absorption spectra of other studied carotenoids. A change in the ground-state electronic structure of IV, due to the influence of water near the terminal dicyanomethylidene group, is proposed to be the major reason for this large band shift.

Kinetics of Fusion and Fragmentation Nonionic Micelles: Triton X-100

We describe the kinetics of exchange of a pyrene-labeled triglyceride 1 between micelles of Triton X-100, an octylphenol ethoxylate with a mean degree of ethoxylation of 9.5. These micelles have an aggregation number of ca. 110 surfactants/micelle and are capable of solubilizing more than four molecules of 1 per micelle while maintaining Poisson solubilization statistics. When excess surfactant is added to a solution of TX100 micelles containing sufficient 1 that the fluorescence spectrum is dominated by excimer emission, the monomer emission intensity grows in at the expense of excimer emission. Since 1 is insoluble in water, exchange requires fusion of two micelles followed by fragmentation. This process follows second-order kinetics, from which we calculate a second-order rate constant kfus = 1.15 × 106 M-1 s-1. Micelle fusion is approximately 5000-fold slower than diffusion controlled. We infer that the barrier to micelle fusion is due primarily to entropic and hydration effects of the ethylene oxide ...

Kinetics of interaction of Histidine and Histidine Methyl Ester with Ninhydrin in micellar media

Kinetics of the interaction of histidine and histidine methyl ester with ninhydrin under varying concentrations of reactants, anionic (sodium dodecyl sulphate, SDS), cationic (cetyltrimethylammonium bromide, CTAB) and non-ionic (Triton X-100, TX-100) micelles have been carried out. Rate of the reaction was found to be independent of the initial concentration of histidine (and histidine methyl ester) but was dependent on [Ninhydrin]. The SDS micelles had no effect on the rate of the reaction. In the presence of the CTAB micelles a small enhancement in the rate was observed. The rate − [CTAB] profile showed that the increase in [CTAB] increased the rate up to a maximum value and a further increase had a decreasing effect on the rate. The rate was enhanced by TX-100 also but, unlike CTAB micelles, TX-100 possessed a curve without peak for the rate − [TX-100] profile. The following rate equation was obeyed by the reaction in CTAB and TX-100 micelles: Values of kw, km, and KS were evaluated and are reported herein. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 103–111, 1999

Interaction of N-alkyl styryl pyridinium dyes with TX-100 in aqueous medium: Role of the alkyl chain during solubilisation

Interaction of a series of N-alkyl styryl pyridinium dyes having varied alkyl chain (Cn) with nonionic surfactant (Triton X-100) solution has been studied by using absorption and emission techniques. The binding constants of the dyes (C1–C18) with the surfactant aggregates have been calculated and found to increase with increasing alkyl chain length of the dyes. A decrease in the CMC value of TX-100 in presence of the dyes with increasing chain length has been observed and the phenomenon is attributed to the increasing hydrophobicity of the additive. The relative ET(30) values of the local environment of the dyes in TX-100 micelles with respect to standard solvents have been determined. A solubilisation strategy of the micelle for the dyes has been reported where the cationic head group remains in the oxyethylene cage of the micelle and the hydrophobic tail remains buried in the micellar core due to pulling effect.

Analysis of Polydispersity of Mixed Micelles of TX-100/SDS and C12E8/SDS by Capillary Electrophoresis

Capillary electrophoresis (CE) was used to study the polydispersity of TX-100/SDS and C12E8/SDS micelle systems. Compared with other techniques, CE provides more specific and graphically detailed information on the compositional polydispersity of such micellar systems. Clear evidence of the coexistence of micelles rich in either nonionic or anionic component has been obtained. This coexistence is explained by considering that the stability of mixed micelles is affected by several factors, including counterion binding, and steric shielding of the electrostatic repulsive interaction among the headgroups of SDS by the bulky EO groups of TX-100. Due to these two factors, micelles with different compositions may be energetically equivalent, leading to a broad distribution of micelle size and composition. In this study, we observe how the pattern of the distribution changes with the mole fraction of SDS. Electrophoretographic patterns also showed that broader compositional distribution of the original components produces a wider distribution of mobilities.

Investigation of the structure of the adsorption layer of nonionic surfactant TX-100 and of the pyrogenic dispersive silica surface genesis using the phototransfer reaction

The influence of a silica (aerosil) surface on the reaction kinetics of a photoinduced electron transfer and quenching of fluoresence of pyrene (Py) in the presence of N,N-dimethylaniline (DMA) when adsorbed from hexane has been studied. A photoreaction between Py and DMA is observed; over a wide range the quenching of the Py fluorescence obeys a Stern-Volmer equation mainly. When Py and DMA are solubilized in aqueous micelles of TX-100 and then adsorbed on an aerosil surface, the influence of the surface on the photoreaction kinetics is negligible. Removal of water from the above system leads to the suppression of the photoreaction. The apparently abnormally long lifetime of Py may be explained by a rearrangement of an adsorption layer, micelle degradation, and encapsulation of the fluorophore.

Photoinduced electron transfer between molecules in silica matrices

The reactions of electron transfer between anthracene (An), pyrene (Py) and fluorescence quenchers N,N-dimethylaniline (DMA), N,N-diethylaniline (DEA) and Cu2+ ions in heterogeneous systems on the basis of silica under the conditions of differing mobilities of molecules and changes of carrier structure have been studied. Quenching of An* and Py* by DEA and DMA on adsorption from hexane on the surface of pyrogenic nonporous silica-aerosil is accompanied by exciplex formation and concentrational dependence of the rate constant of quenching. Fluorescence of solubilized Py is quenched very strongly by adding DMA in adsorbed TX-100 micelles. Removal of water sharply changes the photonics of the system. Intensity of Py fluorescence remains high and no quenching occurs. Py molecules are encapsulated in the SiO2 between layers of hydrophobic parts of TX-100. Photoinduced electron transfer between Py* and Cu2+ is effective at the stage of sol-gel transition in tetraethoxysilane (TEOS) hydrolysis reaction. Py molecules trapped in porous sol-gel phases are shown to undergo photoinduced electron transfer with Cu2+ when the liquid phase is present inside the pores.

Photochromism and thermochromism of spiro[indolinoxazines] in normal and reversed and reversed micelles

Spectra, photochromism and thermochromism of a spiro[indoline-naphthoxazine] and a spiro[indoline-phenanthroxazine] have been investigated in cationic (CTAB, hexadecyltrimethylmmonium bromide) and non-ionic (TX-100) micellar solutions and in sodium bis-2-ethylhexylsulfosuccinate (AOT)/toluene/water inverted-micelles. The spectral shifts of the photomerocyanine colour band provided information on the location of the molecules in these systems. From photokinetic study of the colour-forming and colour-fading reactions, the quantum yield and bleaching constant were determined. The thermal equilibrium constant of the spiro[indoline-phenanthroxazine] was spectrophotometrically measured. Comparison of the results obtained in microheterogeneous systems with those determined in a homogeneous solution indicated that thermo- and photo-colourability increase in TX-100 and CTAB micelles and decrease in inverted micelles.