Articles de revues : « CATIONIC MICELLES »

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Wasylishen, Roderick E., Jan C. T. Kwak, Zhisheng Gao, Elisabeth Verpoorte, J. Bruce MacDonald et Ross M. Dickson. « NMR studies of hydrocarbons solubilized in aqueous micellar solutions ». Canadian Journal of Chemistry 69, n^o 5 (1 mai 1991) : 822–33. http://dx.doi.org/10.1139/v91-122.

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Information concerning the solubilization of hydrocarbons in ionic surfactant micelles was obtained from 2H NMR relaxation, 1H NMR chemical shifts, and 1H NMR paramagnetic relaxation measurements. The rotational motion of deuterated hydrocarbons, which is related to the micellar microviscosity at the location of the hydrocarbons, was probed by 2H NMR relaxation. The relaxation data are interpreted using both the two-step and the single-step models, and the results are discussed in terms of the micellar microviscosity and the location of the hydrocarbons in micelles. The location of the hydrocarbons in micelles was further investigated by determining the aromatic ring current-induced 1H chemical shifts along the surfactant alkyl chain and by comparing the 1H spin-lattice relaxation enhancement of the hydrocarbons and the surfactant alkyl chain, induced by Mn2+ on the micellar surface. The hydrocarbons used include benzene, naphthalene, acenaphthalene, triphenylene, cyclohexane, cyclododecane, and tert-butylcyclohexane and the surfactants studied are hexadecyl-, tetradecyl-, and dodecyltrimethylammonium bromide; hexadecyl-, tetradecyl-, and dodecylpyridinium halide; and sodium dodecyl sulfate. The results indicate that the micellar microviscosity at the location of saturated hydrocarbons is approximately 5 cP for both the cationic and anionic micelles, whereas the micellar microviscosity at the location of unsaturated hydrocarbons is much higher. The unsaturated hydrocarbons are found to reside primarily near the surfactant headgroup in the cationic micelles, but are distributed evenly throughout the anionic SDS micelles. The saturated hydrocarbons appear to be located in the interior of the micelles. Key words: NMR, relaxation, solubilization, surfactant, micelle.

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Kumar, Abanish. « SN2 Mechanism of Cationic Micelles on the Hydrolysis of Bis-p-Methoxyphenyl Phosphate Ester ». Pakistan Journal of Scientific & ; Industrial Research Series A : Physical Sciences 58, n^o 3 (26 octobre 2015) : 117–21. http://dx.doi.org/10.52763/pjsir.phys.sci.58.3.2015.117.121.

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Hydrolysis of bis-p-methoxyphenyl phosphate ester (bis-p-MPPE) was studied in micellar solutions of cityltrimethylammoniumbromide n-C16H33N+(CH3)3Br- (CTABr) at pH-9.0. The hydrolysis followed first order kinetics with respect to bis-p-MPPE concentration. At the concentration of critical micelle concentration (CMC) the rate of hydrolysis increased with increasing CTABr concentration. Surfactant with cationic or polar head group form micelles in water with hydrocarbon like interior or polar groups at the surface and bind cationic solute. The binding constant of micelle for bis-p-MPPE and the rate constant in micellar pseudo phase were determined from kinetic data using the pseudophase model.

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Hosseinzadeh, Reza, Mohammad Gheshlagi, Rahele Tahmasebi et Farnaz Hojjati. « Spectrophotometric study of interaction and solubilization of procaine hydrochloride in micellar systems ». Open Chemistry 7, n^o 1 (1 mars 2009) : 90–95. http://dx.doi.org/10.2478/s11532-008-0078-4.

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AbstractThe interaction of Procaine hydrochloride (PC) with cationic, anionic and non-ionic surfactants; cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and triton X-100, were investigated. The effect of ionic and non-ionic micelles on solubilization of Procaine in aqueous micellar solution of SDS, CTAB and triton X-100 were studied at pH 6.8 and 29°C using absorption spectrophotometry. By using pseudo-phase model, the partition coefficient between the bulk water and micelles, Kx, was calculated. The results showed that the micelles of CTAB enhanced the solubility of Procaine higher than SDS micelles (Kx = 96 and 166 for SDS and CTAB micelles, respectively) but triton X-100 did not enhanced the solubility of drug because of weak interaction with Procaine. From the resulting binding constant for Procaine-ionic surfactants interactions (Kb = 175 and 128 for SDS and CTAB surfactants, respectively), it was concluded that both electrostatic and hydrophobic interactions affect the interaction of surfactants with cationic procaine. Electrostatic interactions have a great role in the binding and consequently distribution of Procaine in micelle/water phases. These interactions for anionic surfactant (SDS) are higher than for cationic surfactant (CTAB). Gibbs free energy of binding and distribution of procaine between the bulk water and studied surfactant micelles were calculated.

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Jeyarajan, Helen Ratna Monica. « PHOTOPHYSICAL ASPECTS OF POLARITY SENSITIVE FLUOROPHORE IN CATIONIC REVERSE MICELLES ». Journal of Advanced Scientific Research 13, n^o 01 (10 février 2022) : 340–47. http://dx.doi.org/10.55218/jasr.202213140.

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In recent years, the field of reverse micelles has witnessed a significant growth of interest, partly due to the finding that proteins, other biopolymers, and even bacterial cells can be solubilized in the reverse micellar systems. Among surfactants capable of forming water in oil microemulsion, the cationic surfactant cetyltrimethylammonium bromide (CTAB) has received particular attention because of its ability to solubilize relatively large amount of water in a variety of hydrophobic organic solvents. Due to versatile photochemical and photophysical properties of Ru(II) complexes, Ru(II)- phenanthroline and its derivatives were used in this present work to form CTAB cationic reverse micelles and studied to characterise their photophysical properties such as absorption, emission and excited state life time. The findings from the spectral data observed in the present study proves that the excited state properties of Ru(II)-phenanthroline complexes are dramatically altered in the presence of reverse micelle. Specifically reverse micelle encapsulation of [Ru(dpphen)3]2+ complex in restricted environment causes blue shift in the emission maximum as well as have longer radiative lifetime. The blue shift in the emission maximum in the case of [Ru(dpphen)3]2+ indicates that the probes are near the water in oil reverse micellar interface, tightly bound and are not displaced towards the water pool of the micelle even at the highest water loading W0=50, which reveals the increased hydrophobicity. This highest fluorescence lifetime can serve as an excellent indicator to point out the location of the probe in a microheterogeneous system/environment.

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Wang, Jing, Xueqing Xing, Xiaocui Fang, Chang Zhou, Feng Huang, Zhonghua Wu, Jizhong Lou et Wei Liang. « Cationic amphiphilic drugs self-assemble to the core–shell interface of PEGylated phospholipid micelles and stabilize micellar structure ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 371, n^o 2000 (13 octobre 2013) : 20120309. http://dx.doi.org/10.1098/rsta.2012.0309.

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Since polymeric micelles are promising and have potential in drug delivery systems, people have become more interested in studying the compatibility of polymeric carriers and drugs, which might help them to simplify the preparation method and increase the micellar stability. In this article, we report that cationic amphiphilic drugs can be easily encapsulated into PEGylated phospholipid (PEG–PE) micelles by self-assembly method and that they show high encapsulation efficiency, controllable drug release and better micellar stability than empty micelles. The representative drugs are doxorubicin and vinorelbine. However, gemcitabine and topotecan are not suitable for PEG–PE micelles due to lack of positive charge or hydrophobicity. Using a series of experiments and molecular modelling, we figured out the assembly mechanism, structure and stability of drug-loaded micelles, and the location of drugs in micelles. Integrating the above information, we explain the effect of the predominant force between drugs and polymers on the assembly mechanism and drug release behaviour. Furthermore, we discuss the importance of p K a and to evaluate the compatibility of drugs with PEG–PE in self-assembly preparation method. In summary, this work provides a scientific understanding for the reasonable designing of PEG–PE micelle-based drug encapsulation and might enlighten the future study on drug–polymer compatibility for other polymeric micelles.

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Ezhilrani, V. C., Vigneshwari R et Sasmita Dash. « Comparison Between Interaction of Hydrophobic-anionic and Hydrophobic-cationic Mixed Micellar System with Drug Ciprofloxacin ». Oriental Journal Of Chemistry 37, n^o 6 (30 décembre 2021) : 1376–86. http://dx.doi.org/10.13005/ojc/370616.

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The interaction studies of drug ciprofloxacin with two mixed micellar systems are reported. The mixed micelles comprise a nonionic hydrophobic surfactant, pluronic L-81, an anionic surfactant, Ammonium dodecyl sulfate (ADS); and a cationic surfactant, Cetylpyridinium bromide (CPB). The various combinations chosen were L-81-ADS and L-81-CPB. The properties of both the mixed micelles were compared. Spectrophotometric, conductometric, co-solvent effect, and Infrared studies were used for the investigations. The studies were carried out in a wide range of mixed micellar concentrations in the post micellar region of the individual surfactants. The solubilization of drug CPX in the L-81-ADS was higher than that in L-81-CPB mixed micelle, as evidenced by UV studies. Ethanol and ethylene glycol were found to be effective co-solvents for both the mixed micellar systems. The conductivity studies of CPX with ADS and CPB surfactants, displayed a higher value of conductance for CPX and ADS, from 0.37µs-1 to 0.74µs-1 compared to CPX and CPB. The drug-mixed micelle displayed a higher molecular weight complex formation as seen from the IR spectra.

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Favaro, Yvette L., et Vincent C. Reinsborough. « Micellar catalysis in mixed anionic/cationic surfactant systems ». Canadian Journal of Chemistry 72, n^o 12 (1 décembre 1994) : 2443–46. http://dx.doi.org/10.1139/v94-310.

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Dye solubility and stopped-flow kinetic studies were conducted in sodium dodecylsulfate/dodecyltrimethylammonium bromide and sodium dodecylsulfate/decyltrimethylammonium bromide micellar solutions with excess anionic surfactant. The enhanced rate in the presence of anionic micelles of the Ni2+(aq)/pyridine-2-azo-p-dimethylaniline (PADA) complexation reaction was used as a probe of the mixed micellar situation. PADA solubilities and the kinetic parameters derived through the Robinson model for micellar catalysis were consistent with a complete incorporation of the cationic surfactant into the sodium dodecylsulfate micelles.

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Pilgrová, Tereza, et Miloslav Pekař. « Interaction between Cationic Micelles and Hyaluronan ». Materials Science Forum 851 (avril 2016) : 26–31. http://dx.doi.org/10.4028/www.scientific.net/msf.851.26.

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Micelles are particles of colloidal dimension and it is known that in an aqueous phase can solubilize water insoluble molecules (hydrophobic biologically active substances) in their inner core. However surfactants may have adverse effects on biological structures. Association of micelles with suitable bioacceptable molecules (e.g. hyaluronan) may lead to enhance their biocompatibility, decrease the nanoparticles cytotoxicity and also to target to the specific receptors in a human body. In this study, results of the research of electrostatic coating of cationic micelle with hyaluronan are reported. The cationic micelle/hyaluronan complexes were studied using turbidimetry and dynamic light scattering method and were evaluated to determine their structure, average size and zeta potential as a function of the amount of the both component in the system. Turbidimetric titration was chosen as indicator of the loss of intensity of transmitted light due to the scattering effect of particles associated from hyaluronan and surfactant in it. Dynamic light scattering measurement provided information about size distribution and zeta potential during mixing of component. Pilot solubilization experiments were performed to evaluation of stability and solubilization ability of the complexes. Results of turbidimetry revealed that aggregates formation (turbidity increasing) depends especially on hyaluronan concentration while surfactant concentration (above critical micelle concentration) affects interaction insignificantly. Dynamic light scattering experiments indicate that hyaluronan molecular weight has insignificant effect on isoelectric point of the systems. It was found that solubilization ability of the complexes is influenced by molecular weight of hyaluronan.

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Kim, B. K., K. Baek et J. W. Yang. « Simultaneous removal of nitrate and phosphate using cross-flow micellar-enhanced ultrafiltration (MEUF) ». Water Science and Technology 50, n^o 6 (1 septembre 2004) : 227–34. http://dx.doi.org/10.2166/wst.2004.0380.

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The feasibility of cross-flow micellar-enhanced ultrafiltration (MEUF) was investigated to remove nitrate and phosphate simultaneously. At the above critical micelle concentration (CMC), a cationic surfactant added in wastewater forms micelles, which have positive charge on their surface. Anionic contaminants such as nitrate and phosphate can be bound on the micelles by electrostatic interaction, and the micelle-pollutants complex is removed effectively by ultrafiltration. In this study, a cross-flow MEUF system was designed and investigated the feasibility of MEUF for field application. A cationic surfactant, cetylpyridinium chloride (CPC), was used, and the synthetic wastewater was treated by the polyacrylonitrile membranes with molecular weight cut-off (MWCO) of 30,000 Da and 10,000 Da. With the molar ratio of CPC to total pollutants of > 3, > 86% of nitrate and > 91% of phosphate were removed, respectively, and > 97% of CPC was also rejected. The flux was maintained 20Ð30% of the flux of distilled water. Therefore, it is feasible to remove nitrate and phosphate simultaneously using the cross-flow MEUF system.

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Wang, Tingyi, Hui Yan, Li Lv, Yingbiao Xu, Lingyu Zhang et Han Jia. « Computational Investigations of a pH-Induced Structural Transition in a CTAB Solution with Toluic Acid ». Molecules 26, n^o 22 (19 novembre 2021) : 6978. http://dx.doi.org/10.3390/molecules26226978.

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In this work, molecular dynamics simulations were performed to study the pH-induced structural transitions for a CTAB/p-toluic acid solution. Spherical and cylindrical micelles were obtained for aqueous surfactants at pH 2 and 7, respectively, which agrees well with the experimental observations. The structural properties of two different micelles were analyzed through the density distributions of components and the molecular orientations of CTA+ and toluic acid inside the micelles. It was found that the bonding interactions between CTA+ and toluic in spherical and cylindrical micelles are very different. Almost all the ionized toluic acid (PTA−) in the solution at pH 7 was solubilized into the micelles, and it was located in the CTA+ headgroups region. Additionally, the bonding between surfactant CTA+ and PTA− was very tight due to the electrostatic interactions. The PTA− that penetrated into the micelles effectively screened the electrostatic repulsion among the cationic headgroups, which is considered to be crucial for maintaining the cylindrical micellar shape. As the pH decreased, the carboxyl groups were protonated. The hydration ability of neutral carboxyl groups weakened, resulting in deeper penetration into the micelles. Meanwhile, their bonding interactions with surfactant headgroups also weakened. Accompanied by the strengthen of electrostatic repulsion among the positive headgroups, the cylindrical micelle was broken into spherical micelles. Our work provided an atomic-level insights into the mechanism of pH-induced structural transitions of a CTAB/p-toluic solution, which is expected to be useful for further understanding the aggregate behavior of mixed cationic surfactants and aromatic acids.

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Tian, Maozhang, Xi Chen, Xinyuan Zou, Yuchen Qian, Zhang Liu et Yaxun Fan. « pH-Responsive Rheological Properties and Microstructure Transition in Mixture of Anionic Gemini/Cationic Monomeric Surfactants ». Molecules 26, n^o 16 (19 août 2021) : 5013. http://dx.doi.org/10.3390/molecules26165013.

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Surfactant aggregates have long been considered as a tool to improve drug delivery and have been widely used in medical products. The pH-responsive aggregation behavior in anionic gemini surfactant 1,3-bis(N-dodecyl-N-propanesulfonate sodium)-propane (C12C3C12(SO3)2) and its mixture with a cationic monomeric surfactant cetyltrimethylammonium bromide (CTAB) have been investigated. The spherical-to-wormlike micelle transition was successfully realized in C12C3C12(SO3)2 through decreasing the pH, while the rheological properties were perfectly enhanced for the formation of wormlike micelles. Especially at 140 mM and pH 6.7, the mixture showed high viscoelasticity, and the maximum of the zero-shear viscosity reached 1530 Pa·s. Acting as a sulfobetaine zwitterionic gemini surfactant, the electrostatic attraction, the hydrogen bond and the short spacer of C12C3C12(SO3)2 molecules were all responsible for the significant micellar growth. Upon adding CTAB, the similar transition could also be realized at a low pH, and the further transformation to branched micelles occurred by adjusting the total concentration. Although the mixtures did not approach the viscosity maximum appearing in the C12C3C12(SO3)2 solution, CTAB addition is more favorable for viscosity enhancement in the wormlike-micelle region. The weakened charges of the headgroups in a catanionic mixed system minimizes the micellar spontaneous curvature and enhances the intermolecular hydrogen-bonding interaction between C12C3C12(SO3)2, facilitating the formation of a viscous solution, which would greatly induce entanglement and even the fusion of wormlike micelles, thus resulting in branched microstructures and a decline of viscosity.

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Liu, Jingjing, Airi Yoneda, Dian Liu, Yuuichi Yokoyama, Shin-ichi Yusa et Kenichi Nakashima. « Mixed micelles of poly(styrene-b-3-(methacryloylamino)propyltrimethylammonium chloride-b-ethylene oxide) and anionic amphiphiles in aqueous solutions ». Canadian Journal of Chemistry 88, n^o 3 (mars 2010) : 208–16. http://dx.doi.org/10.1139/v09-159.

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The micelles of poly(styrene-b-3-(methacryloylamino)propyltrimethylammonium chloride-b-ethylene oxide) (PS-b-PMAPTAC-b-PEO) have been successfully prepared in aqueous solutions. The micelles have a PS core, cationic PMAPTAC shell, and PEO corona. Due to the short PS chain (degree of polymerization = 8), the formation of micelles is difficult at a low concentration, and the micelles are detected only at concentrations higher than 1 g L–1. The addition of anionic amphiphiles, such as sodium dodecyl sulfate (SDS) and poly(methacrylic acid) (PMAA), induces the formation of mixed micelles at a low concentration level of the polymer (~0.005 g L–1). This can be ascribed to insolubilization of the cationic PMAPTAC block due to charge neutralization by the anionic amphiphiles. The binding of SDS or PMAA to the PMAPTAC block is confirmed by zeta-potential measurements. The mixed micelles are characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), and fluorescence measurements. Based on DLS measurements, it is revealed that the hydrodynamic diameter of the mixed micelles falls in the range of 120–130 nm. SEM measurements provided clear pictures of mixed micelles with a spherical morphology. The kinetics of exchange of organic dyes between the micelle particles was investigated by fluorescence techniques. The result indicates that the exchange of the dyes between the micelle particles takes places within a time scale of seconds.

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Hosseinzadeh, Reza, et Mohammad Gheshlagi. « Interaction and micellar solubilization of diclofenac with cetyltrimethylammonium bromide : A spectrophotometric study ». Collection of Czechoslovak Chemical Communications 74, n^o 3 (2009) : 503–13. http://dx.doi.org/10.1135/cccc2008021.

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In this study, the interaction of diclofenac (Dic) with cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated. The effect of cationic micelles on solubilization of diclofenac in aqueous micellar solution was studied at pH 6.8, 29 °C and various drug concentrations. The binding of diclofenac to CTAB micelles was accompanied by a batochromic shift in the drug absorption spectra. The solubility of diclofenac increased with increasing surfactant concentration as a consequence of the association between the drug and micelles. From the results, the binding constants Kb, was obtained. By using the pseudo-phase model, the partition coefficient between the bulk water and CTAB micelles, Kx, and the Gibbs energy of binding were calculated. The value of binding constant and partition coefficient are increased by increasing of diclofenac concentration.

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ul Haq, Naveed, Muhammad Usman, Ajaz Hussain, Zahoor Hussain Farooqi, Muhammad Saeed, Sadia Hanif, Muhammad Irfan, Mohammad Siddiq et Usman Ali Rana. « Partitioning of reactive yellow 86 between aqueous and micellar media studied by differential absorption spectroscopy ». Canadian Journal of Chemistry 95, n^o 6 (juin 2017) : 697–703. http://dx.doi.org/10.1139/cjc-2016-0442.

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The present study describes the partitioning of a reactive dye, reactive yellow 86, between aqueous and micellar media of a cationic surfactant (cetyltrimethyl ammonium bromide, CTAB), as well as an anionic surfactant (sodium dodecyl sulphate, SDS). In a systematic investigation, we have recorded the UV–vis absorption spectra of the dye as a function of surfactant’s concentration above and below the critical micelle concentration (CMC). Absorption spectra display a red shift in the case of CTAB and a hypochromic shift upon using SDS. The partition coefficient (Kx) was calculated using differential absorption data, and the value of free energy of partition (ΔGp) was calculated using this Kx value. The results revealed that the dye is solubilized in CTAB micelles to a greater extent than in SDS micelles.

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Malkawi, Ahmad, Nasr Alrabadi et Ross Allan Kennedy. « Dual-Acting Zeta-Potential-Changing Micelles for Optimal Mucus Diffusion and Enhanced Cellular Uptake after Oral Delivery ». Pharmaceutics 13, n^o 7 (27 juin 2021) : 974. http://dx.doi.org/10.3390/pharmaceutics13070974.

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Context: Overcoming the intestinal mucosal barrier can be a challenge in drug delivery. Nanoemulsions with negative zeta potentials can effectively permeate the mucus layer, but those with positive zeta potentials are better taken up by cells; a nanoemulsion with capricious zeta potential from negative to positive can achieve both good permeation and high uptake. Objective: This study aimed to develop dual-acting zeta-potential-amphoteric micelles enabling optimal muco-permeation and enhancement of cellular uptake. Methods: A micellar pre-concentrate was prepared from 15% Labrasol, 15% Kolliphor EL, 30% Kolliphor RH 40, and 40% dimethylsulfoxide. The micellar pre-concentrate was loaded with anionic stearic acid (SA), forming ionic complexes with cationic polymers at a ratio of 25:1 with Eudragit RS 100 and Eudragit RL 100. Blank micelles and those containing complexes were separately diluted in physiological buffers and examined for their droplet sizes, polydispersity indices (PDIs), zeta potentials, and cytotoxicity. The SA release from the micellar complexes was evaluated in 0.1 mM phosphate buffer (pH 6.8) containing 0.001% fluorescein, thereby enabling an instant decrease in fluorescence. Finally, the micelles were loaded with the model drug fluorescein diacetate (FDA) and evaluated for their muco-permeation behavior and cellular uptake. Results: The micellar dilutions formed micelles at the critical micelle concentration (CMC) of 312 µg/mL and showed a uniform average droplet size of 14.2 nm, with a PDI < 0.1. Micellar dilutions were non-cytotoxic when used at 1:100 in a physiological medium. Micelles loaded with ionic complexes achieved a sustained release of 95.5 ± 3.7% of the SA in 180 min. Moreover, the zeta potential of the complex-loaded micelles shifted from −5.4 to +1.8 mV, whereas the blank micelles showed a stabilized zeta potential of −10 mV. Furthermore, the negatively charged blank and complex-loaded micelles exhibited comparable muco-permeation, with an overall average of 58.2 ± 3.7% diffusion of FDA. The complex-loaded micellar droplets, however, provided a significantly higher cellular uptake of the model drug FDA (2.2-fold, p ≤ 0.01) Conclusion: Due to undergoing a shift in zeta potential, the modified micelles significantly enhanced cellular uptake while preserving mucus-permeating properties.

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Fuentes, Irma, Patricio Silva, Francisco Martinez et Andrés F. Olea. « Solubilization of Phenol Derivatives in Polymer Micelles Formed by Cationic Block Copolymer ». Journal of Nanomaterials 2017 (2017) : 1–8. http://dx.doi.org/10.1155/2017/7187324.

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The aggregation of cationic block copolymers formed by polystyrene (PS) and poly(ethyl-4-vinylpyridine) (PS-b-PE4VP) was studied in aqueous solution. Diblock copolymers of PS and poly(4-vinylpyridine) were synthesized by sequential anionic polymerization using BuLi as initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PS-b-PE4VP block copolymers with different quaternization degree. The self-aggregation of cationic block copolymers was studied by fluorescence probing, whereas the morphology and size of polymer micelles were determined by transmission electronic microscopy. Results indicate that spherical micelles with sizes lower than 100 nm were formed, whereas their micropolarity decreases with increasing quaternization degree. The partition of phenols between the micellar and aqueous phase was studied by using the pseudo-phase model, and the results show that the partition coefficients increase with increasing length of the side alkyl chain and are larger for star micelles. These results are discussed in terms of three-region model.

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Rashid, Sadaf, Muhammad Usman, Tanvir Shahzad, Muhammad Saeed, Atta Ul Haq, Muhammad Ibrahim, Muhammad Siddiq et Misbah Iram. « The Differential Spectroscopic Investigation of Partitioning of Reactive Dyes in Micellar Media of Cationic Surfactant, Cetyl Trimethylammonium Bromide (CTAB) ». Zeitschrift für Physikalische Chemie 233, n^o 2 (25 février 2019) : 183–99. http://dx.doi.org/10.1515/zpch-2018-1142.

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Abstract This manuscript reports the solubilization of two reactive dyes viz. reactive black-5 (RB-5) and reactive black-8 (RB-8) in the micellar media of cationic surfactant, cetyl trimethylammonium bromide (CTAB) by differential UV/visible spectroscopy. Absorption spectra of said dyes in the presence of CTAB provide strong evidence about dye–surfactant interaction. In premicellar region ion association pair is formed between dye and surfactant while in post micellar region dye molecules get accommodated within the micelles. The values of critical micelle concentration (CMC) of CTAB in the presence of dyes, partition coefficient; Kx, free energy of partition, ∆Gp, binding constant, Kb and free energy of binding, ∆Gb were determined and compared for both dyes. It is, thus, concluded that RB-5 is solubilized to greater extent than RB-8 because of its incorporation in palisade layer of micelle close to micelle-water interface.

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Dahadha, Adnan A., Mohammed Hassan, Tamara Mfarej, Razan Bani Issa, Mohamed J. Saadh, Mohammad Al-Dhoun, Mohammad Abunuwar et Nesrin T. Talat. « The Catalytic Influence of Polymers and Surfactants on the Rate Constants of Reaction of Maltose with Cerium (IV) in Acidic Aqueous Medium ». Journal of Chemistry 2022 (1 juillet 2022) : 1–11. http://dx.doi.org/10.1155/2022/2609478.

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Kinetics of the reaction of maltose with cerium ammonium sulfate were analyzed spectrophotometrically by observing the decrease of the absorbance of cerium (IV) at 385 nm in the presence and absence of polyethylene glycols (600, 1500, and 4000) and polyvinylpyrrolidone (PVP), in addition to anionic micelles of sodium dodecyl sulfate (SDS), cationic micelles of cetyltrimethylammonium bromide (CTAB) and non-ionic micelles of Tween 20 surfactants. Generally, there is little literature about using the polymers (PEGs and PVP) as catalysts in the oxidation-reduction reactions. Therefore, the major target of this work was to investigate the influence of the nature of polymers and surfactants on the oxidation rates of maltose by cerium (IV) in acidic aqueous media, as well as employing the Piszkiewicz model to explain the catalytic effect. The kinetic runs were derived by adaptation of the pseudo first-order reaction conditions with respect to the cerium (IV). The reaction was found to be first-order with respect to the oxidant and fractional-order to maltose and H2SO4. The reaction rates were enhanced in the presence of polymer and micellar catalysis. Indeed, the surfactants were found to work perfectly close to their critical micelle concentrations (CMC). Electrostatic interaction and H-bonding appear to play an influential role in binding maltose molecules to polymer/surfactant micelles, while oxidant ions remain at the periphery of the Stern layer within the micelle.

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Greencorn, David J., Victoria M. Sandre, Emily K. Piggott, Michael R. Hillier, A. James Mitchell, Taryn M. Reid, Michael J. McAlduff, Kulbir Singh et D. Gerrard Marangoni. « Asymmetric cationic gemini surfactants : an improved synthetic procedure and the micellar and surface properties of a homologous series in the presence of simple salts ». Canadian Journal of Chemistry 96, n^o 7 (juillet 2018) : 672–80. http://dx.doi.org/10.1139/cjc-2017-0676.

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The micellar and morphological properties of symmetric, cationic gemini surfactants have been well studied in the literature as a function of nature and type of the spacer group and the length and type of hydrophobic chain. In this paper, we have examined the effects of tail asymmetry on the properties of a series of cationic surfactants, the N-alkyl-1-N′-alkyl-2-N,N,N′,N′-tetramethyldiammonium dibromide. A novel synthetic method is used to prepare a series of these surfactants and the consequences of asymmetry on micellar properties are presented. This new method has been shown to be more efficient, with higher yields of the asymmetric surfactants than the yields of the accepted literature method. The critical micelle concentration values and the micelle sizes of the asymmetric gemini surfactants, 12-4-12, 12-4-10, 12-4-8, and 12-4-6 gemini surfactants, were obtained from conductivity and dynamic light scattering. With increasing chain asymmetry, the size of the micelle increased due to the formation of loose micelles. The addition of NaCl and Na2SO4 to the surfactant solutions increased the aggregate size, and this effect was more pronounced with increasing salt concentrations. These results are interpreted in terms of the effect these ions have on the “compactness” of the micelle structure.

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Jeong, Ji Hoon, Sun Hwa Kim, Sung Wan Kim et Tae Gwan Park. « Intracellular Delivery of Poly(ethylene glycol) Conjugated Antisense Oligonucleotide Using Cationic Lipids by Formation of Self-Assembled Polyelectrolyte Complex Micelles ». Journal of Nanoscience and Nanotechnology 6, n^o 9 (1 septembre 2006) : 2790–95. http://dx.doi.org/10.1166/jnn.2006.414.

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A polyelectrolyte complex (PEC) micelle-based antisense oligodeoxynucleotide (ODN) delivery system was designed to overcome intrinsic limitations of cationic lipid-mediated gene transfer. Cationic lipid (Lipofectamine™, LF) and ODN conjugated poly(ethylene glycol) (PEG) were ionically complexed to form self-assembled spherical PEC micelles. They have a distinctive structural feature: a charge-neutralized core surrounded by highly flexible PEG corona. The PEC micelles could be visualized as a nano-sized sphere by atomic force microscopy (AFM). The DNA/LF PEC micelles exhibited far improved transfection efficiency compared to those of conventional lipoplex formulations (ODN/LF) in the presence of serum. They showed enhanced cellular uptake followed by rapid nuclear localization of ODN in human epithelial carcinoma (KB) cells. In addition, anti-proliferative activity of c-raf gene-directed antisense ODN was almost fully maintained in KB cells in the presence of serum.

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Liu, Rui, WanFen Pu, Hu Jia, XiaoPei Shang, Yue Pan et ZhaoPeng Yan. « Rheological Properties of Hydrophobically Associative Copolymers Prepared in a Mixed Micellar Method Based on Methacryloxyethyl-dimethyl Cetyl Ammonium Chloride as Surfmer ». International Journal of Polymer Science 2014 (2014) : 1–14. http://dx.doi.org/10.1155/2014/875637.

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A novel cationic surfmer, methacryloxyethyl-dimethyl cetyl ammonium chloride (DMDCC), is synthesized. The micellar properties, including critical micelle concentration and aggregation number, of DMDCC-SDS mixed micelle system are studied using conductivity measurement and a steady-state fluorescence technique. A series of water-soluble associative copolymers with acrylamide and DMDCC are prepared using the mixed micellar polymerization. Compared to conventional micellar polymerization, this new method could not only reasonably adjust the length of the hydrophobic microblock, that is,NH, but also sharply reduce the amount of surfactant. Their rheological properties related to hydrophobic microblock and stickers are studied by the combination of steady flow and linear viscoelasticity experiments. The results indicate that both the hydrophobic content and, especially the length of the hydrophobic microblock are the dominating factors effecting the intermolecular hydrophobic association. The presence of salt influences the dynamics of copolymers, resulting in the variation of solution characters. Viscosity measurement indicates that mixed micelles between the copolymer chain and SDS molecules serving as junction bridges for transitional network remarkably enhance the viscosity. Moreover, the microscopic structures of copolymers at different experimental conditions are conducted by ESEM. This method gives us an insight into the preparation of hydrophobically associative water-soluble copolymers by cationic surfmer-anionic surfactant mixed micellar polymerization with good performance.

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Dutta, Robin K., et Subray N. Bhat. « Association of neutral red with micelles and its effect on the pKa ». Canadian Journal of Chemistry 71, n^o 11 (1 novembre 1993) : 1785–91. http://dx.doi.org/10.1139/v93-221.

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The interactions of neutral red with cationic surfactants, viz., N-hexadecylpyridinium chloride and alkyltrimethylammonium bromides; a nonionic surfactant, viz., Triton X100; and an anionic surfactant, viz., sodium dodecyl sulfate, were investigated spectroscopically. The equilibrium constants for the association of the indicator with the micelles were determined from the apparent association constants at constant pH at 298 K. The effects of the indicator-micelle association on the apparent pKa of the indicator in aqueous surfactant solutions are discussed. It was shown that the apparent pKa of the indicator in cationic surfactant solution can be predicted from knowledge of the indicator-micelle association constant.

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Broxton, Trevor J., et Robin A. Coa. « Micellar catalysis of organic reactions. Part 33. Amide hydrolysis in neutral solution in the presence of a copper-containing micelle ». Canadian Journal of Chemistry 71, n^o 5 (1 mai 1993) : 670–73. http://dx.doi.org/10.1139/v93-090.

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The hydrolysis of 5-nitro-2-(trifluoroacetylamino)benzoic acid (1) has been studied at pH 7 in water and in the presence of micelles of cetyltrimethylammonium bromide (ctab) and of copper-containing micelles formed from the reaction of N,N,N′-trimethyl-N′-hexadecylethylenediamine and cupric chloride. It has been found that the hydrolysis of 1 is inhibited by micelles of ctab but strongly catalysed by the copper-containing micelle at this pH. At a higher pH where the hydroxide ion reaction becomes important the reaction is catalysed by micelles of ctab as well, but the catalysis is stronger by the copper-containing micelle. The effect of added sodium chloride on the rate of reaction is shown to be larger for reaction in the presence of ctab than for reaction in the presence of the copper micelles. Also reported are the effects of the buffer concentration on the rate of reaction at various pH for both micelles. It is concluded that the mechanism of reaction in the copper-containing micelle involves a metal-bound hydroxyl rather than a free hydroxide ion loosely associated with the cationic micelle surface. It is interesting that the catalysis of this reaction by the copper-containing micelle is large enough to allow amide hydrolysis at a reasonable rate at neutral pH at ambient temperature.

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Jadhao, Manojkumar, Soham Mukherjee, Ritika Joshi, Himank Kumar et Sujit Kumar Ghosh. « Aggregation–disaggregation pattern of photodynamically active ZnPcS4 and its interaction with DNA alkylating quinone : effect of micellar compactness and central metal ion ». RSC Advances 6, n^o 81 (2016) : 77161–73. http://dx.doi.org/10.1039/c6ra13151d.

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The graphical abstract shows the aggregation–disaggregation pattern of ZnPcS₄ in neutral and different cationic micelles and its enhanced interaction with a DNA alkylating quinone in a TTAB micellar medium.

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Bunton, Clifford A., et Angela Cuenca. « Micellar effects upon reactions of the 2,2′,4,4′,4″-pentamethoxytrityl cation with nucleophiles ». Canadian Journal of Chemistry 64, n^o 6 (1 juin 1986) : 1179–83. http://dx.doi.org/10.1139/v86-195.

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Cationic micelles of cetyltrimethylammonium chloride and bromide (CTACl and CTABr) speed attack of water upon the 2,2′,4,4′,4″-pentamethoxytrityl cation by a factor of ca. 5. The first-order rate constant in water is 5.51 s−1 at 25.0 °C. Anionic micelles of sodium dodecyl sulfate (SDS) have little effect on this reaction, but they strongly inhibit attack of OH−. In water, second-order rate constants for attack of OH−, CN−, and N3− are, respectively, 235, 177, and 2.8 × 105 M−1 s−1. Rate constants of reaction in CTACl go through maxima with increasing [surfactant] and analysis of the data shows that second-order rate constants at the micellar surface are similar to those in water.

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Paraiso, West Kristian D., Jesús García Chica, Xavier Ariza, Jordi García, Kazunori Kataoka, Rosalía Rodríguez Rodríguez et Sabina Quader. « A New Nanomedicine Platform to Deliver a Carnitine Palmitoyl-Transferase 1 (CPT1) Inhibitor into Glioma Cells and Neurons ». Materials Proceedings 4, n^o 1 (12 novembre 2020) : 58. http://dx.doi.org/10.3390/iocn2020-07986.

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Obesity and glioblastoma multiforme (GB) are two unmet medical needs where effective therapies are lacking. Carnitine palmitoyl transferase 1 (CPT1), an enzyme catalyzing the rate-limiting step in fatty acid oxidation (FAO), is a viable target for both diseases. C75, a fatty acid synthase (FAS) inhibitor, forms an adduct with coenzyme A (CoA) to form C75-CoA, which is a strong competitive inhibitor to CPT1 that is selective in its target. However, it is polar and charged, having low cell membrane permeability, and therefore needing a delivery system for intracellular transport. (±)-C75-CoA and its enantio-separated forms (+)- and (−)-C75-CoA were used to form poly-ion complex (PIC) micelles with the cationic block co-polymer PEG-PAsp(DET). The drug and polymer were mixed in a 1:1 anion/cation ratio to give 50–70 nm micelles with a unimodal size profile and narrow polydispersity. Size was maintained upon introduction of physiological saline. Micellar (±)-, (+)-, and (−)-C75-CoA were all significantly more cytotoxic compared to the respective free drugs in U87MG. We examined whether C75-CoA inhibits FAO by measuring ATP concentrations in U87MG and GT1-7. ATP generation was found to be hampered after adding C75-CoA in both cell types, with micelle-treated cells producing significantly lower ATP than those treated with free drug, suggesting that the effective intracellular delivery of C75-CoA leads to a more pronounced FAO inhibition. A fluorescent CoA derivative, Fluor-CoA, also yielded monodisperse micelles similar to C75-CoA. Micellar internalization was significantly greater than that of the free dye. Uptake of both increased with time, with this effect is more pronounced in U87MG than GT1-7. The %Fluor-CoA+ cells were also expressively higher for the micelle across cell lines. From this data, it can be convincingly concluded that neuronal and glioma cellular uptake of micelles is superior to that of the free dye, validating the need for cellular delivery systems for anionic, CoA-type molecules. The micellar form neutralized the negative charge of the cargo, promoting transport into the cell. These outcomes strongly support the effectiveness of using a PIC micelle-type system to deliver anionic small molecules into glioma cells and neurons meant to inhibit enzymes such as CPT1, for future applications in diseases like obesity and cancer.

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Aisha, Uzma, Qamruzzaman et M. Z. A. Rafiquee. « Kinetics of Reduction of Colloidal MnO2 by Glyphosate in Aqueous and Micellar Media ». International Journal of Inorganic Chemistry 2011 (5 avril 2011) : 1–6. http://dx.doi.org/10.1155/2011/243519.

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The kinetics of the reduction of colloidal MnO2 by glyphosate has been investigated spectrophotometrically in an aqueous and micellar (cetyltrimethylammonium bromide, sodium lauryl sulfate) media. The reaction follows first-order kinetics with respect to colloidal MnO2 in both the aqueous and micellar media. The rate of oxidation increases with increase in [glyphosate] in the lower concentration range but becomes independent at its higher concentrations. The addition of both the anionic (NaLS) and cationic (CTAB) micelles increased the rate of reduction of colloidal MnO2 by glyphosate while the nonionic TX-100 micelles did not influence the rate of reaction. In both aqueous and micellar media, the oxidation of glyphosate occurs through its adsorption over colloidal MnO2 surface. The reaction in micellar media was treated by considering the pseudophase model. The values of reaction rates and binding constants in the presence of micelles were determined.

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Naeem, Kashif, Syed Shah, Bushra Naseem et Syed Shah. « Interactions of short chain phenylalkanoic acids within ionic surfactant micelles in aqueous media ». Journal of the Serbian Chemical Society 77, n^o 2 (2012) : 201–10. http://dx.doi.org/10.2298/jsc110121182n.

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% SDS KR nema Solubilization and interactions of phenylalkanoic acids induced by cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic surfactant, sodium dodecyl sulfate (SDS) was investigated spectrophotometrically at 25.0?C. The UV spectra of the additives (acids) were measured with and without surfactant above and below critical micelle concentration (cmc) of the surfactant. The presence of alkyl chain in phenylalkanoic acids is responsible for hydrophobic interaction resulting in shift of the spectra towards longer wavelength (red shift). The value of partition coefficient (Kx) between the bulk water and surfactant micelles and in turn standard free energy change of solubilization (?Gp?) were also estimated by measuring the differential absorbance (?A) of the additives in micellar solutions.

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Nguyen, Hau Thi, Wen-Shing Chang, Nguyen Cong Nguyen, Shiao-Shing Chen et Hau-Ming Chang. « Influence of micelle properties on micellar-enhanced ultrafiltration for chromium recovery ». Water Science and Technology 72, n^o 11 (14 août 2015) : 2045–51. http://dx.doi.org/10.2166/wst.2015.370.

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An investigation of micelle properties on the recovery of chromium for micellar enhanced ultrafiltration (MEUF) process was conducted using cationic surfactant of cetyltrimethylammonium bromide (CTAB). The relationship between degree of ionization, micellar sizes and chromium removal were determined in this study. The results showed that the complete ionization for CTA+ and Br− was observed for CTAB lower than 0.72 mM and aggregation initiated at concentration of CTAB higher than 0.72 mM to yield attraction of counterion. The micellar sizes increased with increase in concentration of CTAB (higher than 4.02 mM) to generate micron-sized micelles. The distribution of micellar sizes was used to estimate the molecular weight cutoff of membrane used in the MEUF process. As chromium was added into aqueous CTAB solution, the chromate was dominant and bound on the micellar surface instead of Br−. Moreover, the presence of micelle formed a gel-layer to slightly shrink the membrane pore, therefore, UF membrane of 30k Da molecular weight cutoff (pore size ≈ 7.9 nm) was selected in the MEUF process to achieve the removal efficiency of Cr(VI) higher than 95%.

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CELEJ, M. Soledad, Mariana G. D'ANDREA, Patricia T. CAMPANA, Gerardo D. FIDELIO et M. Lucia BIANCONI. « Superactivity and conformational changes on alpha-chymotrypsin upon interfacial binding to cationic micelles ». Biochemical Journal 378, n^o 3 (15 mars 2004) : 1059–66. http://dx.doi.org/10.1042/bj20031536.

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The catalytic behaviour of α-CT (α-chymotrypsin) is affected by cationic micelles of CTABr (hexadecyltrimethylammonium bromide). The enzyme–micelle interaction leads to an increase in both the Vmax and the affinity for the substrate p-nitrophenyl acetate, indicating higher catalytic efficiency for bound α-CT. The bell-shaped profile of α-CT activity with increasing CTABr concentrations suggests that the micelle-bound enzyme reacts with the free substrate. Although more active with CTABr micelles, the enzyme stability is essentially the same as observed in buffer only. Enzyme activation is accompanied by changes in α-CT conformation. Changes in tertiary structure were observed by the increase in intensity and the red shift in the α-CT tryptophan fluorescence spectrum, suggesting the annulment of internal quenching and a more polar location of tryptophan residues. Near-UV CD also indicated the transfer of aromatic residues to a more flexible environment. CTABr micelles also induces an increase in α-helix, as seen by far-UV CD and FTIR (Fourier-transform infrared) spectroscopies. The far-UV CD spectrum of α-CT shows an increase in the intensity of the positive band at 198 nm and in the negative band at 222 nm, indicating an increased α-helical content. This is in agreement with FTIR studies, where an increase in the band at 1655 cm−1, corresponding to the α-helix, was shown by fitting analysis and difference spectroscopy. Spectral deconvolution indicated a reduction in the β-sheet content in micelle-bound α-CT. Our data suggest that the higher catalytic efficiency of micelle-bound α-CT results from significant conformational changes.

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Vaid, Zuber S., Arvind Kumar, Omar A. El Seoud et Naved I. Malek. « Drug induced micelle-to-vesicle transition in aqueous solutions of cationic surfactants ». RSC Advances 7, n^o 7 (2017) : 3861–69. http://dx.doi.org/10.1039/c6ra25577a.

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Solubilization of the drug diclofenac sodium (DS) in micellar aggregates of ionic liquid-based surfactants and cetyltrimethylammonium bromide at 25 °C induces changes to worm-like micelles and vesicles, with potential use in drug delivery.

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Broxton, TJ, JR Christie et SM Mannas. « Micellar Catalysis of Organic-Reactions. XXI. A Comparison of the Catalytic Activity of Micelles of Cetyltrimethylammonium Bromide and Sulfate on Ester, Amide and Carbamate Hydrolyses ». Australian Journal of Chemistry 41, n^o 3 (1988) : 325. http://dx.doi.org/10.1071/ch9880325.

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The basic hydrolyses of phenyl acetate, N,4-dimethyl-N-(3′- nitrophenyl ) benzamide , methyl N-methyl-N-(4′-nitrophenyl) carbamate and methyl N-(3′,5′-dinitrophenyl)-N-methylcarbamate have been studied in cationic micelles of cetyltrimethylammonium bromide (ctab) and sulfate (ctas). Hydrolysis of phenyl acetate and the 4′-nitro carbamate, which involve rate-determining hydroxide attack, exhibit weak catalysis by both micelles, and the observed rates in each micelle are similar. The hydrolysis of the benzamide and the 3′,5′-dinitro carbamate, which involve rate determining C-N bond breaking, show larger catalysis, and, furthermore, micelles of ctab are more effective than micelles of ctas. The observed rates can be explained by the pseudo-phase kinetic model. For reactions involving rate-determining hydroxide attack, the calculated second-order rate constants in micelles of ctab and ctas are similar and much less than those for reaction in water. For reactions involving rate-determining C-N bond breaking the calculated second-order rate constants in micelles of ctab are greater than in micelles of ctas, and similar to those for reaction in water.

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Kochkodan, Olga, Victor Maksin, Nadiya Antraptseva et Tetyana Semenenko. « Molecular Interactions in Binary Surfactant Solutions : Effect of pH ». Periodica Polytechnica Chemical Engineering 64, n^o 4 (25 juillet 2019) : 437–45. http://dx.doi.org/10.3311/ppch.13975.

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By using surface tension and conductivity measurements, the colloid-chemical properties of the mixtures of cationic hexadecylpyridinium bromide with nonionic Triton X-100 surfactants were investigated both in the bulk solution and at air/solution interface at different pH values. The composition of mixed micelles and adsorption layers, parameters of molecular interactions in mixed micelles βm and adsorption layers βσ, as well as standard free energies of micelle formation ΔG0mic and adsorption ΔG0ads were calculated. It was found that molecules of the nonionic surfactant presumably dominate in the mixed micelles and adsorption layers. It was shown that βm and βσ have negative values, which indicate the strengthening of intermolecular interactions in the mixed micelles and adsorption layers. Based on the data obtained, it was suggested that ion-dipole interactions are involved in the formation of intermolecular structures between nonionic and cationic surfactants in aqueous solution and at the air-solution interface. It was shown that βm, βσ as well as ΔG0mic and ΔG0ads parameter depends on the solution pH value. The complex interplay of ion-dipole, protonation and chelation processes, which occur in the surfactant mixtures at different pH and affect the strength of intermolecular interaction, should be taken into account for data analysis.

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Haram, Santosh K., Anand R. Mahadeshwar et Sharad G. Dixit. « Synthesis and Characterization of Copper Sulphide Nanoparticles in Aqueous Surfactant Solutions ». Adsorption Science & ; Technology 16, n^o 8 (septembre 1998) : 667–77. http://dx.doi.org/10.1177/026361749801600807.

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Copper sulphide nanoparticles were synthesized by reacting a copper-ammonia complex with thiourea in aqueous micellar solutions of cationic, non-ionic and anionic surfactants. A blue shift in the absorption spectra revealed the formation of size-quantized nanoparticles. The influence of micelles in mediating the stabilization was studied by carrying out the reactions in surfactant solutions above and below the critical micelle concentration. The effect of thiourea on the stability of the nanoparticles was studied by synthesizing the nanoparticles at different mole ratios of reactants. Characterization of the nanoparticles was achieved by the use of transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray microanalysis (EDAX) and UV–vis spectroscopy.

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Broxton, TJ. « Micellar Catalysis of Organic Reactions. XXXI. A Study of the Effects of Micelles of Cetyltrimethylammonium Bromide on Some SNAr Reactions in Aqueous Binary Mixtures ». Australian Journal of Chemistry 44, n^o 5 (1991) : 667. http://dx.doi.org/10.1071/ch9910667.

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The effect of micelles of cetyltrimethylammonium bromide ( ctab ) on the SNAr reactions of 1-fluoro-2,4-dinitrobenzene (1), 2-fluoro-5-nitrobenzoate (2) and 4-fluoro-3-nitrobenzoate (3) with sodium hydroxide in aqueous binary mixtures with several alcohols has been studied. Two products were detected in all of these reactions: the phenol from reaction with hydroxide ions, and an aryl alkyl ether from reaction with the alkoxide ions. Micelles of ctab increased the percentage yield of the ether product at the expense of the phenol for compounds (1) and (2) in most of the binary mixtures used. For compound (3), however, micelles of ctab had little effect on the product distribution. These differences were attributed to differences in the orientation of substrates (2) and (3) when solubilized by micelles of ctab . Very high yields of the ether were obtained for the reaction of compound (1) with hydroxide ions in trifluoroethanol /water mixtures, and this was attributed to the considerable ionization of trifluoroethanol which was the most acidic alcohol used in this work. The lowest yield of the ether product was obtained in reactions of compound (1) with hydroxide ions in propan-2-ol/water mixtures since propan-2-ol was the least acidic alcohol used. These results are compared with those previously reported for the reaction of compound (1) in the presence of hydroxy-functionalized micelles and β- cyclodextrin. In the presence of micelles of ctab the aryl alkyl ethers derived from compounds (1) and (2) underwent a subsequent SNAr reaction with hydroxide ions during which the alkoxide ion was displaced. For compound (3) no subsequent reaction of the ether was detected in the presence of micelles of ctab . This was also attributed to the orientation of this product within the micelle. The reaction centre was buried in the micellar interior, and hence was shielded from a subsequent reaction. The rates of this subsequent reaction for compound (1), and of the decomposition of micellar aryl ethers and of cyclodextrin aryl ethers derived from compound (1), are also compared. The increase in the yield of the ether product in the presence of micelles was attributed to the increased ionization of alcohols in the presence of cationic micelles.

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Ortega, Francisco, et Elvira Rodenas. « Counterion micellar effects upon the reaction of low-spin diimine iron(II) complexes ». Canadian Journal of Chemistry 67, n^o 2 (1 février 1989) : 305–9. http://dx.doi.org/10.1139/v89-050.

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The rate of reaction of tris(1,10-phenanthroline)iron(II) ion (1a), tris(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II) ion (1b), and tris(4,7-diphenhyl-1, 10-phenanthroline)iron(II) ion (1c) with hydroxide ion, in cationic micelles, is strongly affected by the concentration of micellar counterion in solution. The reaction of la in CTACl is modestly speeded up by the addition of added KCl, while the reactions of 1b and 1c are strongly inhibited by the addition of large amounts of KCl and KBr to micellar solutions of CTACl and CTABr, respectively. These rate effects fit the pseudophase-ion exchange model, assuming the binding of the substrates to the micelles depends upon the counterion concentration. Keywords: counterion micellar effects, low-spin diimine iron(II) complexes.

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Dolcet, C., et E. Rodenas. « An electrostatic approach to negatively charged substrate reactions with hydroxide ion in cationic CTAB micelles ». Canadian Journal of Chemistry 68, n^o 6 (1 juin 1990) : 932–38. http://dx.doi.org/10.1139/v90-145.

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An electrostatic treatment is presented to explain the experimental kinetic data we obtained for the basic hydrolysis of the negatively charged substrates acetylsalicylic acid and 3-acetoxy-2-naphthoic acid. This treatment, based on the non-linearized Poisson–Boltzmann equation, considers specific interactions between the counterions and the micellar surface and explains the displacement of these substrates from the micellar to the aqueous phase through bromide counterion addition. Keywords: electrostatic approach, cationic CTAB micelles.

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Khan, Mohammad Niyaz, et Ibrahim Isah Fagge. « Kinetics and Mechanism of Cationic Micelle/Flexible Nanoparticle Catalysis : A Review ». Progress in Reaction Kinetics and Mechanism 43, n^o 1 (mars 2018) : 1–20. http://dx.doi.org/10.3184/146867818x15066862094905.

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The aqueous surfactant (Surf) solution at [Surf] > cmc (critical micelle concentration) contains flexible micelles/nanoparticles. These particles form a pseudophase of different shapes and sizes where the medium polarity decreases as the distance increases from the exterior region of the interface of the Surf/H2O particle towards its furthest interior region. Flexible nanoparticles (FNs) catalyse a variety of chemical and biochemical reactions. FN catalysis involves both positive catalysis ( i.e. rate increase) and negative catalysis ( i.e. rate decrease). This article describes the mechanistic details of these catalyses at the molecular level, which reveals the molecular origin of these catalyses. Effects of inert counterionic salts (MX) on the rates of bimolecular reactions (with one of the reactants as reactive counterion) in the presence of ionic FNs/micelles may result in either positive or negative catalysis. The kinetics of cationic FN (Surf/MX/H2O)-catalysed bimolecular reactions (with nonionic and anionic reactants) provide kinetic parameters which can be used to determine an ion exchange constant or the ratio of the binding constants of counterions.

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Aluani, Denitsa, Magdalena Kondeva-Burdina, Alexandra Tosheva, Krassimira Yoncheva et Virginia Tzankova. « Improvement of in vitro antioxidant activity of kaempferol by encapsulation in copolymer micelles ». Pharmacia 69, n^o 1 (5 janvier 2022) : 25–29. http://dx.doi.org/10.3897/pharmacia.69.e77678.

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Antioxidant capacity of poorly soluble natural antioxidant kaempferol, in particular free or loaded in two types of cationic micelles, was studied on non-enzyme induced lipid peroxidation (LPO) in vitro. The micelles were based on triblock copolymers - poly(2-(dimethylamino)ethyl methacrylate-b-poly(propylene oxide)-b-poly(2-(dimethylamino)ethyl methacrylate (PDMAEMA-PPO-PDMAEMA) and poly(2-(dimethylamino)ethyl methacrylate-b-poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate (PDMAEMA-PCL-PDMAEMA). The lipid peroxidation was induced by incubating of rat liver microsomes with iron sulphate and ascorbic acid (Fe2+/AA). The effect of free and micellar kaempferol (at concentrations 25, 50 and 75 μg/ml) was assessed after 20 min incubation time. In the non-enzyme lipid peroxidation model, the kaempferol-loaded micelles significantly decreased the formation of malondialdehyde (MDA). The effect of kaempferol loaded in PDMAEMA-PCL-PDMAEMA micelles was more pronounced, showing an improved antioxidant activity in the conditions of oxidative stress and lipid peroxidation in vitro.

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Fagge, Ibrahim I., W. Hamdah W. Ahmad, Sharifuddin Md Zain et M. Niyaz Khan. « Kinetics and Mechanism of Counterionic Salt-Catalysed Piperidinolysis of Anionic Phenyl Salicylate in the Presence of Cationic–Nonionic Mixed Micelles ». Progress in Reaction Kinetics and Mechanism 43, n^o 1 (mars 2018) : 41–52. http://dx.doi.org/10.3184/146867818x15066862094888.

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The quantitative correlation of counterion-affinity to aqueous hexadecyltrimethylammonium bromide (HDAB, cationic micelles/nanoparticles) and the counterion-induced HDAB micellar growth, in the presence of different amounts of poly(ethylene glycol hexadecyl ether) (C16E20, nonionic surfactant), was achieved by the use of a semi-empirical kinetic (SEK) method. The values of the ratio of cationic HDAB, as well as mixed HDAB–C16E20, micellar binding constants of X and Br, KX/ KBr (= KXBr or RXBr) for X = 4-ClC6H4CO2-, were obtained by the SEK method. The concentration range (0.006–0.015 M) of pure HDAB was found to have no influence on the values of KXBr or RXBr. These observations were also recorded upon addition of a nonionic surfactant, C16E20, in an aqueous solution of HDAB. The mean value of KXBr or RXBr obtained in the presence of pure HDAB ( KXBr or RXBr = 50.3) is 2.3 times larger than that in the presence of mixed HDAB–C16E20 (m KXBr or m RXBr = 21.7). From rheometric measurements of aqueous HDA+/4-ClC6H4CO2- with 0.015 M HDAB, single symmetric maxima (at both 25 and 35 °C) were obtained at [4-ClC6H4CO2Na] = 0.03 M. This is evidence for the existence of wormlike micelles/nanoparticles. However, the absence of a maximum in rheometric data for aqueous HDA+/C16E20/4-ClC6H4CO2- with 0.015 M HDAB and 0.006 M C16E20 at various [4-ClC6H4CO2Na] revealed the existence of spherical micelles.

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Li, Ni, et Rui Zhang. « Experimental Research on Apparent Viscosity Behavior of Cationic/Anionic Worm-Like Micelles ». Applied Mechanics and Materials 644-650 (septembre 2014) : 4884–87. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.4884.

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In this paper, cationic surfactant and anionic surfactant form worm-like micelles by self-assembly. The cationic surfactant is acryloxyethyl trimethylammonium chloride (DAC). The anionic surfactant is potassium erucic (KEU). Mixed the cationic surfactant and anionic surfactant, because the DAC molecule contain a double bond, then, polymerized the solution with VA - 044. By contrast many experiments, the purpose is to get the highest apparent viscosity. After comparing, when the molar ratio of n (KEU) : n (DAC) = 5:1, the largest viscosity of worm-like micelles is 1450mPa•s.

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Gamboa, C., A. Olea, H. Rios et M. Henriquez. « Association of alcohol with cationic micelles ». Langmuir 8, n^o 1 (janvier 1992) : 23–26. http://dx.doi.org/10.1021/la00037a006.

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Goto, Masahiro, Ayumi Momota et Tsutomu Ono. « DNA Extraction by Cationic Reverse Micelles ». JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 37, n^o 5 (2004) : 662–68. http://dx.doi.org/10.1252/jcej.37.662.

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Morin, Emmanuelle, Marc Nothisen, Alain Wagner et Jean-Serge Remy. « Cationic Polydiacetylene Micelles for Gene Delivery ». Bioconjugate Chemistry 22, n^o 10 (19 octobre 2011) : 1916–23. http://dx.doi.org/10.1021/bc200083p.

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Skandalis, Athanasios, Anastasiia Murmiliuk, Miroslav Štěpánek et Stergios Pispas. « Physicochemical Evaluation of Insulin Complexes with QPDMAEMA-b-PLMA-b-POEGMA Cationic Amphiphlic Triblock Terpolymer Micelles ». Polymers 12, n^o 2 (3 février 2020) : 309. http://dx.doi.org/10.3390/polym12020309.

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Herein, poly[quaternized 2-(dimethylamino)ethyl methacrylate-b-lauryl methacrylate-b-(oligo ethylene glycol)methacrylate] (QPDMAEMA-b-PLMA-b-POEGMA) cationic amphiphilic triblock terpolymers were used as vehicles for the complexation/encapsulation of insulin (INS). The terpolymers self-assemble in spherical micelles with PLMA cores and mixed QPDMAEMA/POEGMA coronas in aqueous solutions. The cationic micelles were complexed via electrostatic interactions with INS, which contains anionic charges at pH 7. The solutions were colloidally stable in all INS ratios used. Light-scattering techniques were used for investigation of the complexation ability and the size and surface charge of the terpolymer/INS complexes. The results showed that the size of the complexes increases as INS ratio increases, while at the same time the surface charge remains positive, indicating the formation of clusters of micelles/INS complexes in the solution. Fluorescence spectroscopy measurements revealed that the conformation of the protein is not affected after the complexation with the terpolymer micellar aggregates. It was observed that as the solution ionic strength increases, the size of the QPDMAEMA-b-PLMA-b-POEGMA/INS complexes initially decreases and then remains practically constant at higher ionic strength, indicating further aggregation of the complexes. atomic force microscopy (AFM) measurements showed the existence of both clusters and isolated nanoparticulate terpolymer/protein complexes.

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ZELINA, JOHN P., CHRISTOPHER K. NJUE, JAMES F. RUSLING, GEOFFREY N. KAMAU, MIRIAM MASILA et JULIUS KIBUGU. « Influence of Surfactant-based Microheterogeneous Fluids on Aggregation of Copper Phthalocyanine Tetrasulfonate ». Journal of Porphyrins and Phthalocyanines 03, n^o 03 (mars 1999) : 188–95. http://dx.doi.org/10.1002/(sici)1099-1409(199903)3:3<188 ::aid-jpp122>3.0.co;2-a.

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Electronic absorption spectroscopy was used to measure the molecular association of copper phthalocyanine tetrasulfonate in micellar solutions, a microemulsion made with cationic surfactant, and homogeneous solvents. Analysis of absorbance versus concentration data using a multiple-aggregation model and non-linear regression analysis gave values of association constants, molar absorptivities and estimates of average aggregation number. Microemulsions and aqueous micellar solutions made with alkylammonium surfactants inhibited aggregation, probably because of interactions between the phthalocyanine sulfonate groups and the cationic surfactant head groups at interfacial surfaces. Similar aggregation behavior was observed previously in multiple-bilayer films of cationic surfactants. Water and aqueous solutions containing tetraethylammonium bromide or anionic SDS micelles provide environments facilitating extensive aggregation of Cu II PcTS 4−. The major species are dimers in water and acetonitrile/water, but the formation of higher aggregates is promoted by addition of SDS or TEAB. Aprotic organic solvents provide environments intermediate between these two extremes, giving relatively large aggregation numbers (i.e. five to seven) but smaller association constants than aqueous media not containing cationic surfactants.

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Sztucki, Michael, Emanuela Di Cola et Theyencheri Narayanan. « Instrumental developments for anomalous small-angle X-ray scattering from soft matter systems ». Journal of Applied Crystallography 43, n^o 6 (1 octobre 2010) : 1479–87. http://dx.doi.org/10.1107/s002188981003298x.

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An optimized instrument for anomalous small-angle X-ray scattering from charged soft matter is described. The experimental setup takes special care for single-photon detection sensitivity, high energy resolution of the monochromator,in situcalibration of intensity and energy, and the avoidance of radiation damage. Measured intensities are normalized to an absolute scale online, which can be further decomposed to resonant and non-resonant contributions. The performance of the instrument is demonstrated by an example involving cationic surfactant micelles with bromide counter-ions. The counter-ion profile around the micelle is deduced from the analysis of anomalous scattering near theK-absorption edge of bromine. Two different approaches yield similar results for the radial profile of the counter-ions, showing strong condensation of the counter-ions on the micellar surface, in agreement with the inference from electrochemical methods.

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Shrivastava, Alpa, Ajaya Kumar Singh, Neerja Sachdev, Dilip R. Shrivastava et Surendra Prasad. « Micellar oxidative transformation of ciprofloxacin : a kinetic investigation ». Environmental Chemistry 14, n^o 4 (2017) : 231. http://dx.doi.org/10.1071/en17034.

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Environmental contextPollution of the aquatic environment by drugs results not only during their manufacture, but also from the excretion of drug residues and the discharge of expired drugs by households and hospitals. The transformation of ciprofloxacin, one of the leading antibiotic drugs, in the presence of surfactants has been investigated. The results provide a better understanding of how ciprofloxacin degrades in aquatic environments by considering the effect of omnipresent surfactants. AbstractThe kinetics of the oxidative transformation, i.e. oxidative degradation, of ciprofloxacin (CIP) by chloramine-T (CAT) in cationic and anionic micelle media during the water chlorination process was studied spectrophotometrically at 275nm and 298K. The influence of added salts (1–10×10–4moldm–3) and solvent polarity of the medium on the reaction was studied. The orders with respect to substrate CIP and oxidant CAT were found to be first order in each. The variation of acid concentrations showed opposite effects in cationic and anionic micellar aggregates. Liquid chromatography–electrospray ionisation mass spectrometry was used to identify degradation products of CIP, which confirmed the full dealkylation of the piperazine ring in CIP as the major product. The piperazine moiety of CIP is the principal active site for the CAT during oxidation. Activation parameters for the CIP degradation in cationic and anionic micelles were evaluated by studying the reaction at different temperatures, which lent further support to the proposed degradation mechanism for CIP. The rate constants were evaluated to confirm the micellar effect from incorporating sodium dodecyl sulfate and cetyltrimethylammonium bromide in the reaction mixture and the intrinsic reactivity constants were determined in the aqueous as well as in the micellar pseudo-phases as 4.85 and 0.0083.

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Aramaki, Kenji, Eriko Takimoto et Takumi Yamaguchi. « Effect of the Cationic Head Group on Cationic Surfactant-Based Surfactant Mediated Gelation (SMG) ». International Journal of Molecular Sciences 21, n^o 21 (28 octobre 2020) : 8046. http://dx.doi.org/10.3390/ijms21218046.

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The surfactant-mediated gelation (SMG) method allows us to formulate hydrogels using a water-insoluble organogelator. In this study, we formulated hydrogels using three cationic surfactants, hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium chloride (CTAC), and hexadecylpyridinium chloride (CPC)] and an organogelator (12-hydroxyoctadecanoic acid (12-HOA), and studied their structures and mechanical properties. A fiber-like structure similar to that found in the 12-HOA-based organogels was observed by optical microscopy. Small- and wide-angle X-ray scattering profiles showed Bragg peaks derived from the long- and short-spacing of the crystalline structures in the gel fibers and a correlation peak from the surfactant micelles in the small-angle region. Furthermore, the formation of micelles in the hydrogels was confirmed by UV-vis spectroscopic measurements of the gel samples in the presence of Rhodamine 6G. We concluded that the hydrogels prepared by the SMG method in the present systems are orthogonal molecular assembled systems in which two different molecular assembled structures coexist. Among the three surfactant systems, the CTAB system presented the lowest critical gelation concentration and highest sol-gel transition temperature and viscoelasticity. These differences in gel fiber formation and gel properties were discussed from the viewpoint of the degree of solubilization of the gelator molecules in micelles coexisting with gel fibers and diffusion of the gelator molecules in the gel formation process.

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Mutnuru, Kalyana Chakravarthy, et Ramakrishna Karipeddi. « Effect of Cetyltrimethylammonium Bromide and Sodium Dodecyl Sulphate on Oxidation of Indigo Carmine with Potassium Peroxy Diphosphate : A Kinetic and Mechanistic Study ». Asian Journal of Chemistry 34, n^o 11 (2022) : 2994–3000. http://dx.doi.org/10.14233/ajchem.2022.23948.

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The oxidative kinetic study of Indigo carmine (IC) with potassium peroxydiphosphate (PDP) in absence and presence of cationic cetyl-trimethylammonium bromide (CTAB) and anionic sodium dodecyl sulphate (SDS) micelles was studied in an aqueous sulphuric acid medium by maintaining the ionic strength at 3.0 mol dm-3 using sodium sulphate. The pseudo-zero-order constant was determined from the linear plots of absorbance versus time under the conditions [IC] < [PDP]. The reaction obeys zero-order kinetics with respect to varying [IC], first order kinetics with respect to varying [H+] and [PDP] in the absence and in presence of micelles. The reaction rate was accelerated with varying [CTAB] and [SDS] and reached a limiting value. The [surfactant] rate profile has limited nature since the reaction is unimolecular on the micelle surface. The binding constant of peroxy diphosphate was also determined with CTAB and SDS micelles by applying Berezin equation for the kinetic pattern.

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