Micellar Solutions Of Nonionic Surfactants Research Articles

ADSORPTION OF ETHOXYLATED ISONONYLPHENOLS ON CARBON NANOTUBES FROM AQUEOUS SOLUTIONS

One of the approaches to solving the problem of carbon nanotubes dispersions obtaining is the use of nonionic surfactants in the processes of ultrasonication of carbon nanostructures in aqueous solutions. The effect of nonionic surfactants on dispersing and stabilizing is determined by the adsorption interaction of surfactant molecules with a graphene surface, the study of which can reveal important patterns of stable carbon nanotubes dispersions obtaining during ultrasonic treatment in liquid media. The aim of this work was to study the adsorption of ethoxylated isononylphenols with a variable average degree of ethoxylation on single-walled and multi-walled carbon nanotubes from aqueous solutions. The value of adsorption of nonionic surfactants on carbon nanotubes was calculated on the basis of changes in the equilibrium concentration of ethoxylated isononylphenols in the solution at presence of carbon nanotubes. The equilibrium concentration of nonionic surfactants was determined by absorption spectroscopy. It was found that the shape of adsorption isotherms of the ethoxylated isononylphenols on carbon nanotubes from aqueous solutions before ultrasonic treatment corresponds to the Langmuir adsorption isotherm L2. The values of maximum adsorption of ethoxylated isononylphenols were shown to decrease with an increase in the average degree of ethoxylation. Obviously, this is due to conformational changes in the polar chain, showed in the sizes of ethoxylated isononylphenols micelles, in the structure of the adsorption layer. It has been established that the hydrophobic interaction of the surfactants hydrocarbon radical with a graphene surface is the main mechanism for the adsorption of ethoxylated isononylphenols on carbon nanotubes. The dispersions of carbon nanotubes in micellar solutions of nonionic surfactants were obtained and studied. It was shown that ultrasonic treatment leads to a change in the mechanism of nonionic surfactants adsorption on carbon nanotubes.

Solubility of 3-{3,5-Bis(trifluoromethyl)phenyl}quinoline Using Micellar Solutions of Surfactants

Amphiphilic substances, surfactants, are in common use to enhance the aqueous solubility of organic compounds. Solubilization of 3-{3,5-bis (trifluoromethyl)phenyl}quinoline was investigated by employing spectrophotometry, light scattering and tensiometry in micellar solutions of nonionic surfactants {dimethyldodecylamine-N-oxide, DDAO; polyoxyethylene(23)lauryl ether, Brij35; and polyoxyethylene(04)lauryl ether, Brij30}, a cationic surfactant (dodecyltrimethyl-ammonium bromide, DTAB), anionic surfactants (sodium dodecylbenzenesulfonate, SDBS; sodium dodecyl sulfate, SDS), and a zwitterionic surfactant (N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, DDAPS). It is noted that the solubility of the title compound 3-{3,5-bis (trifluoromethyl)phenyl}quinoline increased linearly with the increase in surfactant concentration irrespective of the type of surfactant. This is due to association of the title compound with surfactants. The molar solubilization ratio (MSR), micelle–water partition coefficient (KM), and the Gibbs energy of solubilization (\( \Delta G_{\text{S}}^{\text{o}} \)) of the title compound in the micelles were determined and correlated with each other. The nonionic surfactant DDAO showed the highest solubilization capacity. The order of degree of solubility among nonionic, cationic, and anionic surfactants for 3-{3,5-bis (trifluoromethyl)phenyl}quinoline is DDAO > DDAPS > SDBS > DTAB > SDS > Brij35 > Brij30. This comparative study can be used to select an appropriate medium for the title compound’s solubilization, where the nonionic surfactants DDAO, Brij35 and Brij30 would be more beneficial due to their minimal protein binding and retention of their micellar form even after large dilution in blood owing to their very low critical micellar concentration values. The light scattering study indicated that the hydrodynamic radius of the blank and drug-loaded surfactants remained the same within experimental error.

Study of monoprotic acid–base equilibria in aqueous micellar solutions of nonionic surfactants using spectrophotometry and chemometrics

Many studies have shown the distribution of solutes between aqueous phase and micellar pseudo-phase in aqueous micellar solutions. However, spectrophotometric studies of acid–base equilibria in these media do not confirm such distribution because of the collinearity between concentrations of chemical species in the two phases. The collinearity causes the number of detected species to be equal to the number of species in a homogenous solution that automatically misinterpreted as homogeneity of micellar solutions, therefore the collinearity is often neglected. This interpretation is in contradiction to the distribution theory in micellar media that must be avoided. Acid–base equilibrium of an indicator was studied in aqueous micellar solutions of a nonionic surfactant to address the collinearity using UV/Visible spectrophotometry. Simultaneous analysis (matrix augmentation) of the equilibrium and solvation data was applied to eliminate the collinearity from the equilibrium data. A model was then suggested for the equilibrium that was fitted to the augmented data to estimate distribution coefficients of the species between the two phases. Moreover, complete resolution of concentration and spectral profiles of species in each phase was achieved.

Photochemical properties of substituted tetraazachlorins

The photochemical properties of water-insoluble metal-free tetraazachlorin derivatives in organic solvents and aqueous micellar solutions of nonionic surfactants were investigated. The quantum yields of fluorescence, singlet oxygen generation and photodegradation were evaluated in benzene. The highest photostability and singlet oxygen quantum yield (ΦΔ = 0.7) was found for 2,2,3,3-tetramethyl-7,8,12,13,17,18-hexaphenyltetraazachlorin. The moderate ΦΔ values (0.21–0.35) of triarenotetraazachlorins in benzene were established. Expansion of tetraazachlorin π-system by fusion of three aromatic rings leads to reduction of efficiency of singlet oxygen generation. The study of photodegradation mechanism shows that radical photooxidation apparently is most plausible, though 1 O 2 may partly contribute to photodestruction of some tetraazachlorins. In aqueous colloidal solution of nonionic surfactant (Cremophor EL) the same, as in benzene, effect of sensitizer structure upon efficacy of singlet oxygen production was observed. It was shown that 1 O 2 diffusion from micelle core into solution and then to target slows its oxidation rate substantially in comparison to the case where sensitizer and target are localized in the same micelle.

Micelles and Aggregates of Oxyethylated Isononylphenols and Their Extraction Properties near Cloud Point

We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols--C9H19C6H4O(C2H4O)(n)H, where n = 6, 8, 9, 10, or 12--in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols.

Tube radial distribution phenomenon observed in an aqueous micellar solution of non-ionic surfactant fed into a microspace and an attempt of capillary chromatographic application

A new type of tube radial distribution phenomenon was observed in an aqueous micellar solution of non-ionic surfactant that was fed into a microspace. A homogeneous aqueous solution containing 2 wt % Triton X-100 and 2.0 M sodium chloride was fed into a microchannel (40 μm in depth and 200 μm in width) in a microchip at a flow rate of 4.0 μL/min, where the microchip was maintained at a temperature of 34°C. The homogeneous aqueous solution changed to a heterogeneous solution with two phases in the microchannel; the surfactant-rich phase was generated around the middle of the channel, while the aqueous phase containing little surfactant was formed near the wall. The radial distribution of the surfactant was observed through Rhodamine B dissolved in the aqueous micellar solution with a bright-field microscope — CCD camera system. An open-tubular capillary chromatographic system was also tried to develop using the fusedsilica capillary tube (75 μm inner diameter and 120 cm length) as a separation column and the aqueous micellar solution as a carrier.

Selective photometric determination of nickel, cobal, and zinc in drinking and natural waters using 1-(2-pyridylazo)-2-naphthol and surfactants (SAS)

Selective techniques have been developed for determination of nickel, cobalt, and zinc with 1-(2-pyridylazo)-2-napthol in waters with a lower boundary of determinable concentrations 0.01–0.02 mg/dm3. Reactions took place in micellar solutions of nonionic SAS. Selectivity of determination has been achieved thanks to the use of masking substances and a special procedure of mixing components. Iron does not hinder determination at the concentration < 5 mg/dm3.

Micelle structure and molecular self‐diffusion in isononylphenol ethoxylate–water systems

The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)(n)H (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated.

Adsorption kinetics of non-ionic surfactants in micellar solutions: effects of added charge

The kinetics of adsorption of micellar solutions of non-ionic surfactants have been studied in an overflowing cylinder. The addition of small amounts (< 10% of the total surfactant concentration) of ionic surfactants, CTAB and STS, to solutions of C16E8 causes a dramatic reduction in the rate of adsorption of the nonionic surfactant. The results are rationalised by a combination of monomer and micelle adsorption to the air-water interface. In the presence of trace ionic surfactants, only uncharged micelles adsorb. The adsorption kinetics are independent of the sign of the charge on the micelles, only on its magnitude. The influence of ionic surfactants on the adsorption rate is reversed by addition of millimolar concentrations of salt. Electrolyte screens the repulsions between micelles and the adsorbed monolayer and allows charged micelles to adsorb without first breaking down into monomers.

Tube Radial Distribution Phenomenon Observed in an Aqueous Micellar Solution of Non-ionic Surfactant Fed into a Microspace and an Attempt Of Capillary Chromatographic Application

Tube Radial Distribution Phenomenon Observed in an Aqueous Micellar Solution of Non-ionic Surfactant Fed into a Microspace and an Attempt Of Capillary Chromatographic Application

Rate constants for drug release from micellar solutions of non-ionic surfactants.

The release of weak acid from micellar solutions containing different concentrations of two structurally related non-ionic surfactants was estimated using a dynamic dialysis apparatus. In all cases the effect of the surfactant was to reduce the amount of weak acid transferred. The data have been subjected to compartmental analysis using non-linear regression analysis. Rate constants for exchange cross the dialysis membrane were independent of surfactant concentration. As surfactant concentration increased the rate constants for transfer from the non-micellar region did not show a marked change.

Excitation energy transfer in europium chelate with doxycycline in the presence of a second ligand in micellar solutions of nonionic surfactants

The complexation of Eu3+ with doxycycline (DC) antibiotic in the presence of several second ligands and surfactant micelles of different types is studied by the spectrophotometric and luminescence methods. It is found that the efficiency of excitation energy transfer in Eu3+-DC chelate depends on the nature of the second ligand and surfactant micelles. Using thenoyltrifluoroacetone (TTA) as an example, it is shown that the second ligand additionally sensitizes the europium fluorescence, and the possibility of intermediate sensitization of DC and then of europium is shown by the example of 1,10-phenanthroline. In all cases, the excitation energy transfer efficiency was increased due to the so-called antenna effect. The decay kinetics of the sensitized fluorescence of the binary and mixed-ligand chelates in aqueous and micellar solutions of nonionic surfactants is studied and the relative quantum yields and lifetimes of fluorescence are determined.

Surfactant effects on colloidal interactions: Concentrated micellar solutions of nonionic surfactant

The effect of nonionic surfactants on interaction energies between polystyrene latex or silica spheres and a flat glass surface has been studied using total internal reflection microscopy (TIRM). The measurements reveal that both Triton X-100 and C 12E 5 contribute to the Debye screening length, an effect that is essentially removed on first exposing the surfactants to ion-exchange resin. Whereas particles can be embedded in Triton X-100 concentrations at least as high as 285 times the critical micelle concentration, the same particles become elastically tethered at intermediate separations from the glass surface in somewhat less concentrated micellar solutions of C 12E 5. The elastic energy is caused by a connecting structure between the particle and glass surface, which remains intact on dilution and on lowering the ionic strength of the solvent.

Photodestruction of BDE-99 in micellar solutions of nonionic surfactants of Brij 35 and Brij 58

Currently, soil contamination by polybrominated diphenyl ethers (PBDEs) at e-waste recycling sites in China is of significant environmental concern and requires the identification of appropriate remediation technologies. In this paper, photodestruction of a model PBDE congener (BDE-99) in selected UV/surfactant systems was investigated, using a RPR-200 Rayonet photochemical reactor equipped with two low-pressure mercury lamps. BDE-99 photodegradation in the micellar solutions of nonionic surfactants of Brij 35 and Brij 58 all followed pseudo first-order kinetics and the photodegradation quantum yields were 1.8–2.4 times as high as that in water alone. The photodegradation was comparably enhanced by Brij 35 and Brij 58, and the quenching effect of dissolved oxygen (DO) was eliminated in their presence. Mono- to tetra-BDEs were identified as one group of BDE-99 photoproducts, indicating that one of BDE-99 photodegradation pathways was through a sequential loss of Br. The pattern of PBDE photoproducts showed the photodebromination of BDE-99 readily occurred on the more heavily substituted phenyl ring. Mono- to tetra-polybrominated dibenzofurans (PBDFs) were identified as another group of photoproducts, indicating BDE-99 can also photodegrade through a dibenzofuran-type ring closure process via an intramolecular elimination of HBr. In addition, the formation of these more toxic photoproducts (PBDFs) was not related to the presence of DO. Finally, the later disappearance of mono-BDEs and mono-BDFs suggested the UV exposure time would be an important technical parameter if the technology of UV photodestruction of PBDEs in surfactant micellar solutions is applied to PBDE-contaminated soil remediation.

Complexation of GdIII with tetra-p-tert-butylthiacalix[4]arenoic acid in micellar media

The conditions for the formation of gadolinium(III) complexes possessing high relaxivity with various tetraacid stereoisomers based on p-tert-butylthiacalix[4]arene in micellar solutions of nonionic surfactants were established. The acid-base properties of individual isomers of the ligand were studied by pH-metric titration and UV spectroscopy. The composition and stability constants of the solubilized gadolinium(III) complexes with the obtained thiacalixarenes were determined using computer simulation of the NMR relaxation data.

Length Control in Rigid Cylindrical Nanoassembly by Tuning Molecular Interactions in Aqueous Solutions

We have studied aqueous micellar solutions of nonionic surfactant (pentaethylene glycol mono-n-dodecyl ether, C12E5) doped by cationic surfactant (dodecyl trimethylamoniumbromide, DTAB) as a function of doping level, using small angle neutron scattering. At a doping level of at least 6 mol %, rigid cylindrical micelles formed and the local cylindrical structure of the doped micelles showed no variation across the range of doping levels covered in this study (0-10 mol %). However, the total micellar length decreased rapidly as doping level increased, following well the prediction of micellar aggregation number based on molecular-thermodynamic theory. There was no synergistic interaction between surfactants, leading to monotonically decreasing the micellar aggregation number (shortening of the micellar length).

Ultrafiltration of micellar solutions of nonionic surfactants with or without alachlor pesticide

The ultrafiltration behaviour of micellar solutions of two homologue series of nonionic surfactants was investigated. So, crossflow ultrafiltration experiments were performed using micellar solutions of single surfactant and micellar solutions of surfactant containing alachlor pesticide. Flux reduction, flux recovery, concentration polarization and the effectiveness of MEUF for the removal of alachlor were examined. The effect of surfactant hydrophilic to hydrophobic ratio (characterized by the HLB number) as well as the variation of the surfactant concentration on the flux behaviour characteristics were studied. The observed flux decline and flux recovery values were high and the effect was not due to concentration polarization. The rejection of alachlor achieved was in the range 78–89%.

Adsorption Kinetics in Micellar Solutions of Nonionic Surfactants

Standard models of the adsorption kinetics of surfactants at the air-water surface assume that micelles break down into monomers in the bulk solution and that only monomers adsorb. We show here that micelles of the nonionic surfactant C14E8 adsorb to the surface of a liquid jet at a diffusion-controlled rate. Micellar adsorption can be switched off by incorporation of a small amount of ionic surfactant into the micelle and switched on again by addition of salt. More sophisticated models of adsorption processes in micellar solutions are required that permit a kinetic flux of micelles to the air-water interface.

Selective Synthesis of Single-Crystalline Selenium Nanobelts and Nanowires in Micellar Solutions of Nonionic Surfactants

Single-crystalline nanobelts and nanowires of trigonal selenium (t-Se) have been selectively synthesized in micellar solutions of nonionic surfactants. In particular, t-Se nanobelts about 30 nm in thickness were obtained in micellar solutions of poly(oxyethylene(20)) octadecyl ether (C18EO20), whereas t-Se nanowires were obtained in micellar solutions of poly(oxyethylene(10)) dodecyl ether (C12EO10). The obtained t-Se nanobelts exhibit a low-energy absorption peak that is considerably red shifted from that for t-Se nanowires, which has been presumably attributed to the lower degree of crystal perfection for the t-Se nanobelts with rectangular cross sections.

Calorimetric Study on the Temperature Dependence of the Formation of Mixed Ionic/Nonionic Micelles

The differential excess enthalpy of mixed micelle formation was measured at different temperatures by mixing nonionic hexa(ethylene glycol) mono n-dodecyl ether with anionic sodium dodecyl sulfate or cationic dodecylpyridinium chloride. The experimental data were obtained calorimetrically by titrating a concentrated surfactant solution into a micellar solution of nonionic surfactant. The composition and the size of the mixed nonionic/ionic micelles at different surfactant concentrations were also determined. Pronounced differences in both composition and excess enthalpy were found between the anionic and the cationic mixed system. For both systems, the excess enthalpies become more exothermic with increasing temperature, but for the anionic mixed system an additional exothermic contribution was found which was much less temperature dependent. Temperature dependence of the excess enthalpy was attributed to the effect of the ionic headgroup on the hydration of the ethylene oxide (EO) groups in the mixed corona. Ionic headgroups located in the ethylene oxide layer cause the dehydration of the EO chains resulting in an additional hydrophobic contribution to the enthalpy of mixing. A high affinity of sodium dodecyl sulfate for nonionic micelles and an extra exothermic and less temperature dependent contribution to the excess enthalpy found for the SDS-C(12)E(6) system might be attributed to specific interactions (hydrogen bonds) between the sulfate headgroup and the partly dehydrated EO chain.