Journal articles: 'Catalisi micellare'

1

Broxton, Trevor J. "Micellar Catalysis of Organic Reactions. XXXVIII A Study of the Catalytic Effect of Micelles of 3-Hydroxymethyl-1-tetradecylpyridinium Bromide on Amide Hydrolysis and Nucleophilic Aromatic Substitution." Australian Journal of Chemistry 51, no. 7 (1998): 541. http://dx.doi.org/10.1071/c98053.

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The preparation of 3-hydroxymethyl-1-tetradecylpyridinium bromide and its use as a catalyst of nucleophilic aromatic substitution and also amide hydrolysis are reported. It was found that the hydroxydehalogenation of nitro-activated aryl halides was much faster in these micelles than in the presence of cetyl(2-hydroxyethyl)dimethylammonium bromide. It was concluded that the increased catalysis of nucleophilic aromatic substitution by this micelle was due to a faster decomposition of the aryl micellar ether which must occur before the phenolate product is released. No such difference in the two micelles was found for amide or thioamide hydrolysis since in these reactions the product amine is produced in the first step of the reaction and decomposition of the acylated micelle is not required in the rate-determining step of the reaction.

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2

Broxton, TJ, JR Christie, and RPT Chung. "Micellar Catalysis of Organic Reactions. XXVI. SNAr Reactions of Azide Ions." Australian Journal of Chemistry 42, no. 6 (1989): 855. http://dx.doi.org/10.1071/ch9890855.

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The azidodehalogenation of a number of aromatic compounds has been studied in the presence of micelles of cetyltrimethylammonium bromide (ctab). The variation of the observed rate of reaction with ctab concentration has been treated by using the model of Rodenas and Vera to determine the rate constant for reaction in the micellar pseudo-phase, k2m, the binding constant of the substrate to the micelle, Ks, and the nucleophile-micellar counter ion exchange constant KAzBr :. The ratio of the rate constants in the micellar pseudo-phase and in water varied between 0.9 and 52. For reactions involving the production of a dianionic intermediate the largest catalysis was found for compounds containing two nitro groups to stabilize the double negative charge. In addition significant differences in the catalysis were found between compounds having the reaction centre at the micelle-water interface and those for which the reaction centre was more buried inside the micelle. As previously reported the resulting aryl azides undergo cyclization to form a benzofuroxan if a nitro group is located ortho to the azide group. Furthermore, a reversible photochemical reaction was detected for two compounds having a carboxylate group ortho to the azide group.

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Cibulka, Radek, Lenka Baxová, Hana Dvořáková, František Hampl, Petra Ménová, Viktor Mojr, Baptiste Plancq, and Serkan Sayin. "Catalytic effect of alloxazinium and isoalloxazinium salts on oxidation of sulfides with hydrogen peroxide in micellar media." Collection of Czechoslovak Chemical Communications 74, no. 6 (2009): 973–93. http://dx.doi.org/10.1135/cccc2009030.

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Three novel amphiphilic alloxazinium salts were prepared: 3-dodecyl-5-ethyl-7,8,10-trimethylisoalloxazinium perchlorate (1c), 1-dodecyl-5-ethyl-3-methylalloxazinium perchlorate (2b), and 3-dodecyl-5-ethyl-1-methylalloxazinium perchlorate (2c). Their catalytic activity in thioanisole (3) oxidation with hydrogen peroxide was investigated in micelles of sodium dodecylsulfate (SDS), hexadecyltrimethylammonium nitrate (CTANO3) and Brij 35. Reaction rates were strongly dependent on the catalyst structure, on the type of micelles, and on pH value. Alloxazinium salts 2 were more effective catalysts than isoalloxazinium salts 1. Due to the contribution of micellar catalysis, the vcat/v0 ratio of the catalyzed and non-catalyzed reaction rates was almost 80 with salt 2b solubilized in CTANO3 micelles. Nevertheless, the highest acceleration was observed with non-amphiphilic 5-ethyl-1,3-dimethylalloxazinium perchlorate (2a) in CTANO3 micelles (vcat/v0 = 134). In this case, salt 2a presumably acts as a phase-transfer catalyst bringing hydrogen peroxide from the aqueous phase into the micelle interior. Synthetic applicability of the investigated catalytic systems was verified on semi-preparative scale.

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Drennan, Catherine E., Rachelle J. Hughes, Vincent C. Reinsborough, and Oladega O. Soriyan. "Article." Canadian Journal of Chemistry 76, no. 2 (February 1, 1998): 152–57. http://dx.doi.org/10.1139/v97-226.

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Kinetic studies through stopped-flow spectroscopy were undertaken in the dilute solution range of anionic surfactants where pronounced rate enhancement or inhibition of Ni2+-ligand complexations is often observed at surfactant concentrations much below the critical micelle concentration (CMC). The results are interpreted in terms of Ni-surfactant micelles as the agents responsible for the rate changes in dilute surfactant solution. At higher surfactant concentrations these micelles are transformed into mixed micelles (counterion and size changes), eventually becoming normal surfactant micelles close to the CMC. Surface tension, dye solubility, conductivity, and fluorescent probe investigations support this interpretation.Key words: micellar catalysis, sodium dodecyl sulfate, micelles, critical micelle concentration, premicelles, Ni2+-ligand complexations.

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5

Greencorn, David J., Victoria M. Sandre, Emily K. Piggott, Michael R. Hillier, A. James Mitchell, Taryn M. Reid, Michael J. McAlduff, Kulbir Singh, and 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, no. 7 (July 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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6

MacInnis, Judith A., Greg D. Boucher, R. Palepu, and D. Gerrard Marangoni. "The properties of a family of two-headed surfactant systems: the 4-alkyl-3-sulfosuccinates 2. Surface properties of alkyl sulfosuccinate micelles." Canadian Journal of Chemistry 77, no. 3 (March 1, 1999): 340–47. http://dx.doi.org/10.1139/v99-008.

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The micellar properties of a family of two-headed surfactants, the alkyl sulfosuccinates, were investigated employing fluorescence, ultra-violet spectroscopy, and acid-base titrations, as a function of the chain length of the surfactant. Polarity of the micellar interior was investigated using pyrene and the ionic probe 8-anilino-1-naphthalensulfonic acid ammonium salt (ANS). Pyrene I1/I3 ratios were used to probe the microenvironment of the probe in the palisade layer of the micelle. The pKa values of both of the anionic head groups were determined using acid-base titrations. Surface potential measurements were obtained from the measurement of the pKa of the hydrophobic indicator, 7-hydroxycoumarin, at the sulfosuccinate micellar interface. All of these results were used to examine the surface properties of the alkyl sulfosuccinate micelles and the polarity of the micellar interior.Key words: micellization, pKa, surface potential, surface charge density, 7-hydroxycoumarin, pyrene.

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7

Oranli, Levent, Pratap Bahadur, and Gérard Riess. "Hydrodynamic studies on micellar solutions of styrene–butadiene block copolymers in selective solvents." Canadian Journal of Chemistry 63, no. 10 (October 1, 1985): 2691–96. http://dx.doi.org/10.1139/v85-447.

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Hydrodynamic radius of micelles of several block copolymers in different selective solvents (for both types of blocks) was determined from photon correlation spectroscopy. The boundaries of micellar solutions in heptane (good solvent for polybutadiene block) and dimethylformamide (good solvent for polystyrene block) were established for polymers in terms of their molecular mass and block composition. The photon correlation spectroscopy data in combination with intrinsic viscosities of block copolymers in selective solvents were used to determine micellar molecular mass and aggregation number. The influence of temperature on the micelle size was examined. The block copolymer micelles could solubilize a certain amount of insoluble homopolymer within their insoluble core. 1H nmr spectra were examined to study the influence of temperature on micellar systems.

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8

Wood, Alex B., Daniel E. Roa, Fabrice Gallou, and Bruce H. Lipshutz. "α-Arylation of (hetero)aryl ketones in aqueous surfactant media." Green Chemistry 23, no. 13 (2021): 4858–65. http://dx.doi.org/10.1039/d1gc01572a.

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α-Arylations can be run under micellar catalysis conditions using a Pd(i) pre-catalyst together with KO-t-Bu as base. Sequences using this coupling along with as many as four additional steps can be carried out in a 1-pot fashion, all in water.

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9

MacInnis, Judith A., R. Palepu, and D. Gerrard Marangoni. "A nuclear magnetic resonance investigation of the micellar properties of a series of sodium cyclohexylalkanoates." Canadian Journal of Chemistry 77, no. 11 (November 1, 1999): 1994–2000. http://dx.doi.org/10.1139/v99-211.

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The micellar properties of a family of surfactants, the sodium cyclohexylalkanoates, have been investigated in aqueous solution using multinuclear NMR spectroscopy. C-13 chemical shift measurements have been used to determine both the cmc values and the micellar aggregation numbers (Ns values) of these surfactants. The cmc values and the degrees of counterion binding were estimated from 23Na chemical shift measurements. The critical micelle concentrations (cmc's) and the aggregation numbers determined from the NMR experiments indicate that these amphiphiles have high cmc's and low aggregation numbers when compared to other single-headed surfactants (most notably the sodium alkanoates). The conformational changes incurred by the carbon atoms upon micelle formation have been deduced from the 13C chemical shift differences (δsurf,mic - δsurf,aq). These results are used to discuss the formation of the aggregates of the sodium cyclohexylalkanoate surfactants as a function of the length of the alkanoate side chain.Key words: micelles, surfactants, NMR spectroscopy, chemical shifts, aggregation numbers, degree of counterion binding, conformational changes.

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10

Biasutti, M. A., and Juana J. Silber. "Interaction between tetracyanoethylene and naphthalene in reverse micelles of AOT in n-hexane. The electron-donor properties of AOT." Canadian Journal of Chemistry 74, no. 9 (September 1, 1996): 1603–8. http://dx.doi.org/10.1139/v96-177.

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The electron donor–acceptor (EDA) interaction between TCNE and naphthalene (Naph) in n-hexane and reverse micelles of AOT in n-hexane was studied by UV–visible spectroscopy with the aim of determining the influence of the micellar media on the EDA interaction. The spectra of the mixtures of TCNE–Naph in n-hexane show two typical maxima at 418 and 534 nm, assigned to the formation of a π–π EDA complex. In the micellar media a new band is observed at 398 nm. When the spectra of TCNE in n-hexane are studied in the presence of AOT two new bands at 398 and 418 nm are detected. These bands are consistent with an EDA interaction between TCNE and AOT as n-donor. The stability constants of this interaction were calculated for AOT concentrations below the CMC and in the micellar media at different W(W = [H2O]/[AOT]). The results give evidence of the tendency of AOT to interact very strongly with electron acceptors. Moreover, in the system TCNE–Naph in the micellar media it is shown that Naph and AOT compete to form a complex with TCNE. The formation constants of the complexes of AOT–Naph in the micelle system were determined at W = 0 and 5. Despite the competition of AOT for TCNE the stability constant for the complex TCNE–Naph is higher than in homogeneous media, probably due to the high local concentration of the acceptor in the micelle. Key words: reverse micelles, aerosol-OT, tetracyanoethylene, naphthalene, electron donor–acceptor complexes.

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11

Leaist, Derek G. "Diffusion in associating nonelectrolyte mixtures: stepwise aggregation and micelle formation." Canadian Journal of Chemistry 66, no. 5 (May 1, 1988): 1129–34. http://dx.doi.org/10.1139/v88-185.

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Equations have been developed to predict diffusion coefficients and Onsager coefficients for associating nonelectrolyte solutes in binary or multicomponent solutions with any number of association equilibria. The equations are used to interpret previously reported data for binary diffusion with stepwise association of ethanol and N-methylacetamide in carbon tetrachloride solutions. Diffusion of Triton X-100, a non-ionic micelle-forming surfactant, is also analyzed. In contrast to the gradual decrease in the diffusivity caused by stepwise association, formation of micellar aggregates produces a sharp drop in the diffusivity at the critical micelle concentration. The relation between interdiffusion coefficients and intradiffusion coefficients for associating nonelectrolyte solutes is discussed.

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12

Rispens, Theo, and Jan B. F. N. Engberts. "Micellar Catalysis of Diels−Alder Reactions: Substrate Positioning in the Micelle." Journal of Organic Chemistry 67, no. 21 (October 2002): 7369–77. http://dx.doi.org/10.1021/jo0260802.

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13

Augustine, Rimesh, Dae-Kyoung Kim, Ho An Kim, Jae Ho Kim, and Il Kim. "Poly(N-isopropylacrylamide)-b-Poly(L-lysine)-b-Poly(L-histidine) Triblock Amphiphilic Copolymer Nanomicelles for Dual-Responsive Anticancer Drug Delivery." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 6959–67. http://dx.doi.org/10.1166/jnn.2020.18822.

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A series of ABC triblock poly(N-isopropylacrylamide)75-block-poly(L-lysine)35-block-poly(L-histidine)n (p(NIPAM)75-b-p(Lys)35-b-p(His)N) (N = 35,50,75,100) copolymer bio-conjugates were prepared by combining reversible addition-fragmentation chain transfer polymerization and fast ring-opening polymerization of N-carboxyanhydride a-amino acid using 1,3-dicyclohexylimidazolium hydrogen carbonate as a catalyst. All the resulting triblock copolymers self-assembled into spherical micellar aggregates in aqueous solution, irrespective of the chain length of the histidine block. The micellar aggregates encapsulated the anticancer drug doxorubicin (Dox) and exhibited high drug loading efficiency. Temperature and pH stimuli were applied to investigate the controlled release of Dox. The non-cytotoxic nature of the polymers was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cellular uptake of the Dox-loaded micelles revealed that the micelles successfully release Dox in cancer cells in response to pH- and temperature-induced morphological change. In-vitro studies further confirmed that the Dox-loaded triblock copolymer micelle is an excellent platform for drug delivery.

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14

Wasylishen, Roderick E., Jan C. T. Kwak, Zhisheng Gao, Elisabeth Verpoorte, J. Bruce MacDonald, and Ross M. Dickson. "NMR studies of hydrocarbons solubilized in aqueous micellar solutions." Canadian Journal of Chemistry 69, no. 5 (May 1, 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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15

Rathman, James F. "Micellar catalysis." Current Opinion in Colloid & Interface Science 1, no. 4 (August 1996): 514–18. http://dx.doi.org/10.1016/s1359-0294(96)80120-8.

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16

Venkateswaran, Krishnan, Mary V. Barnabas, Bill W. Ng, and David C. Walker. "Residence-time of muonium at micelles: Effect of added micelles on the reactivity of muonium towards ionic solutes in water." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 1979–83. http://dx.doi.org/10.1139/v88-319.

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The effective rate constant for the reaction of muonium with NO3−, S2O32−, and Tl+ ions in water is altered by the addition of micelles. There is a decrease when the charge on the micelle is the same as that of the solute and an increase when their charges are opposite. From the magnitude of the effect a mean residence-time for muonium of 2 ns has been deduced for dodecyl sulphate micelles. This suggests there is barely any preferred localization, because 2 ns is smaller, even, than the expected diffusion time if the micelle core is as viscous as reported. This use of muonium atoms to probe the dynamics of micelles seems to support the view that there are regions of low microviscosity and considerable water penetration within the micellar structure.

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17

Gebicka, Lidia, and Monika Jurgas-Grudzinska. "Activity and Stability of Catalase in Nonionic Micellar and Reverse Micellar Systems." Zeitschrift für Naturforschung C 59, no. 11-12 (December 1, 2004): 887–91. http://dx.doi.org/10.1515/znc-2004-11-1220.

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Catalase activity and stability in the presence of simple micelles of Brij 35 and entrapped in reverse micelles of Brij 30 have been studied. The enzyme retains full activity in aqueous micellar solution of Brij 35. Catalase exhibits “superactivity” in reverse micelles composed of 0.1 ᴍ Brij 30 in dodecane, n-heptane or isooctane, and significantly lowers the activity in decaline. The incorporation of catalase into Brij 30 reverse micelles enhances its stability at 50 °C. However, the stability of catalase incubated at 37 °C in micellar and reverse micellar solutions is lower than that in homogeneous aqueous solution.

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18

Morini, M. A., P. C. Schulz, and J. E. Puig. "Counterion specificity of the micelle surface and its implications on micellar catalysis." Colloid & Polymer Science 274, no. 7 (July 1996): 662–68. http://dx.doi.org/10.1007/bf00653065.

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19

Hétu, Daniel, and Jacques E. Desnoyers. "Volumes and heat capacities of transfer of ammonium salts from water to aqueous octyldimethylamine oxide at 25 °C." Canadian Journal of Chemistry 66, no. 4 (April 1, 1988): 767–73. http://dx.doi.org/10.1139/v88-133.

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The effect of an additive on a water–surfactant system can be studied through thermodynamic functions of transfer of the additive from water to aqueous solutions of the surfactant. These thermodynamic functions often go through extrema in the region of the critical micellar concentration (cmc) of the surfactant. As it can be shown with a simple chemical equilibrium model, the general shape of the transfer functions is primarily related to the pair-wise hydrophobic interactions between the additive and the surfactant monomers, to a shift in the monomer–micelle equilibrium and to the distribution of the additive between the aqueous phase and the micelles. Medium and electrostatic effects are also possible, especially with ionic systems. To separate these effects and identify the salts which distribute themselves in the micelles, the volumes and heat capacities of transfer of hydrophobic ammonium salts from water to aqueous solutions of dimethyloctylamine oxide have been investigated. The short chain salts have only a small effect on monomer–micelle equilibrium by salting out the monomers, whereas the more hydrophobic ones participate also to the micellization process, shifting more strongly the surfactant monomer–micelle equilibrium.

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20

Barclay, Lawrence Ross Coates, Steven Jeffrey Locke, and Joseph Mark MacNeil. "Autoxidation in micelles. Synergism of vitamin C with lipid-soluble vitamin E and water-soluble Trolox." Canadian Journal of Chemistry 63, no. 2 (February 1, 1985): 366–74. http://dx.doi.org/10.1139/v85-062.

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A study was made of the effect of the inhibitors ascorbic acid (C), α-tocopherol (E), and 6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylate (Trolox, T) on the autoxidation of linoleic acid in 0.50 M sodium dodecyl sulfate (SDS) micelles at pH 7.0 in phosphate buffer. Reactions were thermally initiated at 30 °C in the SDS micelles by a micelle-soluble initiator, di-tert-butylhyponitrite (DBHN). Although water-soluble C alone is an inefficient inhibitor, when combined with micelle-soluble E, it acts synergistically with the latter to extend the efficient antioxidant action of E beyond the sum of the induction periods of C and E acting separately. Similarly C acts synergistically with the water-soluble antioxidant, T. Quantitative studies of these effects under controlled rates of initiation (Ri,) reveal that C functions to regenerate a mole of E (or T) per mole of C used. Kinetic studies show that the rate of autoxidation is first order in micellar linoleic acid and one-half order in micellar DBHN concentrations. Therefore, the classical rate law, −dO2/dt = kp[R—H] (Ri)1/2/(2k1)1/2 is followed. The higher oxidizability (kp/2kt1/2 = 4.48 × 10−2 M−1/2 s−1/2) of linoleate in micelles compared to that in homogeneous solution in chlorobenzene (kp/2kt1/2 = 2.30 × 10−2 M−1/2 s−1/2) is interpreted in terms of the effect of the polar interfacial region of the micelles on a dipolar transition state, R—OŌ: H•R, of the propagation reaction.

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21

Gracie, Kim, Dale Turner, and R. Palepu. "Thermodynamic properties of micellization of sodium dodecyl sulfate in binary mixtures of ethylene glycol with water." Canadian Journal of Chemistry 74, no. 9 (September 1, 1996): 1616–25. http://dx.doi.org/10.1139/v96-179.

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Micellar properties of sodium dodecyl sulfate (SDS) in aqueous mixtures of ethylene glycol (EG) were determined using techniques such as conductivity, density, EMF, surface tension, viscosity, ultrasonic velocity, and spectroscopy (fluorescence). The effective degree of disssociation of micelles (α) was determined using three different methods. Thermodynamics of micellization were obtained from the temperature dependence of critical micelle concentrations (cmc) values. The difference in Gibbs energies of micellization [Formula: see text] of SDS, between water and mixed solvent systems, was calculated to evaluate the influence of cosolvent on the micellization process. Surfactant aggregation numbers (Ns) obtained from static fluorescence quenching methods indicated a decrease in the aggregation numbers with increasing concentration of ethylene glycol in the binary solvent mixtures. In addition, the micropolarity of the micellar interior was determined from the pyreneI1/I3 ratios. These values were consistent with a decrease in the micropolarity surrounding the probe molecule as the EG content in the solvent mixture was increased. Key words: thermodynamics, micellization, aggregation numbers, ultrasonic velocity, degree of dissociation.

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Connolly, Terrence J., and Vincent C. Reinsborough. "Micellar rate enhancement studies in mixed sodium fluorocarbon/hydrocarbon surfactant solutions." Canadian Journal of Chemistry 70, no. 6 (June 1, 1992): 1581–85. http://dx.doi.org/10.1139/v92-194.

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Stopped-flow kinetic studies were conducted in mixed micellar solutions of fluorocarbon and hydrocarbon anionic surfactants to determine the prevalent micellar form. The probe reaction was the Niaq2+/pyridine-2-azo-p-dimethylaniline (PADA) complexation, which is many times accelerated in the presence of anionic micelles. Binding constants for Niaq2+ and PADA partitioning between bulk solution and micelles were determined through the murexide technique and solubility measurements respectively and the molar reaction volume was obtained from the Robinson equation. The three binary surfactant systems investigated had sodium perfluoroheptanoate as the fluorocarbon surfactant while the hydrocarbon surfactants were sodium decylsulfate, sodium nonanesulfonate, and sodium octanesulfonate. The kinetic results were consistent with unimicellar composition in all three systems which was not the behaviour previously found with the sodium octane sulfonate/sodium perfluoroctanoate system. The difference was attributed to closer similarity in the surfactant pair hydrophobicities as revealed through their critical micelle concentrations. Another finding was that mixed micelles synergistically can lead to a much greater solubilization of PADA than is possible through either of the pure surfactants.

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23

Klika Škopić, Mateja, Christian Gramse, Rosario Oliva, Sabrina Pospich, Laura Neukirch, Magiliny Manisegaran, Stefan Raunser, Roland Winter, Ralf Weberskirch, and Andreas Brunschweiger. "Towards DNA‐Encoded Micellar Chemistry: DNA‐Micelle Association and Environment Sensitivity of Catalysis." Chemistry – A European Journal 27, no. 39 (June 7, 2021): 10048–57. http://dx.doi.org/10.1002/chem.202100980.

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PADHY, RANJAN KUMAR, and SREELEKHA DAS BHATTAMISRA. "Surfactant Catalyzed Oxidation of Ethanolamines by Cerium(IV)." Asian Journal of Chemistry 33, no. 1 (2020): 21–25. http://dx.doi.org/10.14233/ajchem.2021.22907.

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Effect of surfactant medium on the kinetics of oxidation of amino alcohol by cerium(IV) has been reported. Two amino alcohols namely, monoethanolamine (MEA) and triethanolamine (TEA) are chosen for kinetic study. Sizeable changes in reaction rate are noted only in presence of sodium lauryl sulphate (NaLS) as surfactant. Both the amino alcohols exhibit rate maxima at around the cmc of NaLS, beyond which the kψ-[NaLS] profile shows slow increase in rate constant with increasing NaLS concentration. Suitable model has been used to explain the kinetic pattern post CMC and from this the micelle-reactant binding constant values have been evaluated. From the temperature dependence study, the activation parameters for the oxidation reactions have been computed and these are compared against those obtained for aqueous medium. Based on all information, plausible mechanism for micellar catalysis has been presented.

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Szutkowski, Kosma, Emilia Sikorska, Iulia Bakanovych, Amrita Roy Choudhury, Andrej Perdih, Stefan Jurga, Marjana Novič, and Igor Zhukov. "Structural Analysis and Dynamic Processes of the Transmembrane Segment Inside Different Micellar Environments—Implications for the TM4 Fragment of the Bilitranslocase Protein." International Journal of Molecular Sciences 20, no. 17 (August 26, 2019): 4172. http://dx.doi.org/10.3390/ijms20174172.

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The transmembrane (TM) proteins are gateways for molecular transport across the cell membrane that are often selected as potential targets for drug design. The bilitranslocase (BTL) protein facilitates the uptake of various anions, such as bilirubin, from the blood into the liver cells. As previously established, there are four hydrophobic transmembrane segments (TM1–TM4), which constitute the structure of the transmembrane channel of the BTL protein. In our previous studies, the 3D high-resolution structure of the TM2 and TM3 transmembrane fragments of the BTL in sodium dodecyl sulfate (SDS) micellar media were solved using Nuclear Magnetic Resonance (NMR) spectroscopy and molecular dynamics simulations (MD). The high-resolution 3D structure of the fourth transmembrane region (TM4) of the BTL was evaluated using NMR spectroscopy in two different micellar media, anionic SDS and zwitterionic DPC (dodecylphosphocholine). The presented experimental data revealed the existence of an α -helical conformation in the central part of the TM4 in both micellar media. In the case of SDS surfactant, the α -helical conformation is observed for the Pro258–Asn269 region. The use of the zwitterionic DPC micelle leads to the formation of an amphipathic α -helix, which is characterized by the extension of the central α -helix in the TM4 fragment to Phe257–Thr271. The complex character of the dynamic processes in the TM4 peptide within both surfactants was analyzed based on the relaxation data acquired on 15 N and 31 P isotopes. Contrary to previously published and present observations in the SDS micelle, the zwitterionic DPC environment leads to intensive low-frequency molecular dynamic processes in the TM4 fragment.

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Vashishtha, Manu, Manish Mishra, and Dinesh O. Shah. "Organobase catalysis using 1-(2-pyrimidyl)piperazine in micellar medium: an approach for better performance and reusability of organobase." Green Chemistry 18, no. 5 (2016): 1339–54. http://dx.doi.org/10.1039/c5gc01966d.

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An efficient and reusable organobase–surfactant micellar catalytic system was formulated for alkali/metal free base catalysis. The 1-(2-pyrimidyl) piperazine (2-PP) base solubilized in the SDS micellar system was demonstrated to be higher in activity as compared to the neat/biphasic/cationic micellar system for the Knoevenagel condensation.

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Koerner, Terry B., and R. S. Brown. "The hydrolysis of an activated ester by a tris(4,5-di-n-propyl-2-imidazolyl)phosphine-Zn2+ complex in neutral micellar medium as a model for carbonic anhydrase." Canadian Journal of Chemistry 80, no. 2 (February 1, 2002): 183–91. http://dx.doi.org/10.1139/v02-001.

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The properties of tris(4,5-di-n-propyl-2-imidazolyl)phosphineM2+ complexes (3M2+, M = Zn, Co) in neutral micellar media of Brij-35 and Triton X-100 have been studied in water with respect to their quantitative potenti metric titration, Co2+-visible absorption spectra, and ability of the 3Zn2+ complex to promote the hydrolysis of the activated ester, p-nitrophenyl acetate (PNPA). Potentiometric titration of the 3M2+(CIO4)2 complexes in 20 mM Brij-35 media yields a steep titration curve indicative of the cooperative consumption of two hydroxides, with computed pK1 and pK2 values of 8.75 and 6.25, respectively, and the midpoint of the titration curve (pKapp) being 7.50. A similar titration of the Co2+ complex also indicates cooperative consumption of two HO, and this is tied to the formation of a 4- or 5-coordinate complex, pKapp ~ 7.37.4. The cooperativity is explained in terms of sequential replacement of the two CIO4 ions associated with the 3M2+ to eventually yield 3M2+HO/(HO(H2O)n) having the first hydroxide ligated to the metal ion and the second associated as an ion pair. The 3Zn2+ complex catalyzes the hydrolysis of PNPA in 20 mM Brij-35 and 40 mM Triton X-100. Plots of the observed second order rate constant (k2) vs. pH in Brij-35 increase linearly with pH and plateau to a value of k2max = 0.86 M1 s1, with a kinetic pKa of 8.7. These data are analyzed by a process wherein the 3Zn2+HO is kinetically active in the rate-limiting step of the reaction, while the ion-paired (HO(H2O)n) exists as a spectator to the slow step, possibly promoting rapid breakdown of a tetrahedral intermediate. Analysis of the kinetic data in terms of a model that accounts for the partitioning of PNPA between water and hydrophobic micellar pseudophase indicates that the second-order rate constant of the micelle-bound ester is augmented by 45-fold due to loading of the PNPA substrate into the micelle. Key words: Brij-35, TritonX-100, neutral micelle, carbonic anhydrase model, kinetics, potentiometric titrations, catalysis, p-nitrophenyl acetate hydrolysis.

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Mullally, Maria K., and D. Gerrard Marangoni. "Micellar properties of zwitterionic surfactant - alkoxyethanol mixed micelles." Canadian Journal of Chemistry 82, no. 7 (July 1, 2004): 1223–29. http://dx.doi.org/10.1139/v04-022.

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The micelle formation process for a zwitterionic surfactant, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3-12), has been investigated in a series of mixed solvents consisting of different concentrations of ethoxylated alcohols and polymers. The critical micelle concentrations (cmc values) of the aggregates were determined by fluorescence spectroscopy, and the surfactant aggregation numbers were obtained from luminescence probing experiments. The cmc values for ZW3-12 changed very little in the presence of increasing amounts of poly(ethyleneoxide) (PEO) in the mixed solvent. In the case of the ethoxylated alcohol ZW3-12 systems, the cmc values and aggregation numbers decreased systematically with increasing alcohol concentration. However, the cmc values of the mixed micelles showed little dependence on the number of ethylene oxide (EO) groups at constant alcohol concentration. These results are compared with the well-studied sodium dodecylsulfate ethoxylated alcohol, and dodecyltrimethylammonium bromide ethoxylated alcohol mixed micellar systems and to SDSPEO systems and are discussed in terms of the contribution of the EO groups to the hydrophobic interactions. Key words: zwitterionic surfactant, alcohols, mixed micelles, luminescence probing.

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Landry, Josette M., D. Gerrard Marangoni, Michael D. Lumsden, and Robert Berno. "1D and 2D NMR investigations of the micelle-formation process in 8-phenyloctanoate micelles." Canadian Journal of Chemistry 85, no. 3 (March 1, 2007): 202–7. http://dx.doi.org/10.1139/v07-008.

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The micellization process of sodium 8-phenyloctanoate in a deuterated aqueous solution was studied, using 1H NMR spectroscopy and two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). 1H NMR spectra, acquired for the sodium 8-phenyloctanoate before and after the critical micelle concentration (CMC) value, showed that large chemical-shift changes were observed for both the aromatic proton peaks and the peaks for the methylene protons near the terminal phenyl group. The plots for the methylene protons near the headgroup do not show these large chemical-shift changes. These observations support the view that the terminal phenyl ring of the surfactant is primarily located in the micellar interior. The 2D NOESY experiments show significant cross-peaks, between the phenyl protons and the methylene protons of the surfactant, that substantiate the conclusions on those drawn from NMR aromatic solute induced shift (ASIS) experiments on the same and similar systems. All these observations are consistent with the Gruen model of the micelle and previous NMR NOESY experiments for other surfactant systems.Key words: surfactants, micelles, NMR, NOESY.

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Márquez-Villa, José Martín, Juan Carlos Mateos-Díaz, Jorge A. Rodríguez, and Rosa María Camacho-Ruíz. "Lipase B from Candida antarctica in Highly Saline AOT-Water-Isooctane Reverse Micelle Systems for Enhanced Esterification Reaction." Catalysts 13, no. 3 (February 28, 2023): 492. http://dx.doi.org/10.3390/catal13030492.

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Butyl oleate synthesis by the lipase B from Candida antarctica (CalB) under extreme halophilic conditions was investigated in the present research through the AOT/Water/Isooctane reverse micellar system. The impact of aqueous content (Wo=H2OSurfactant) and NaCl variation on the enzymatic activity of CalB in the butyl oleate reaction in reverse micelles was explored. The results indicated that, based on the increase of NaCl, it is remarkable to achieve higher enzymatic activity up to 444.85 μmolmin at 5 M NaCl and Wo = 10, as the best esterification conditions at pH 7.2 and 30 °C. However, it was clear that butyl oleate synthesis by lipase CalB increased based on the reduction in the average reverse micelle size, where reverse micelle sizes were determined by dynamic light scattering (DLS). This increase in butyl oleate synthesis demonstrated the potential of reverse micelles as systems that enhance mass transport phenomena in heterogeneous biocatalysis. Furthermore, reverse micelles are promising systems for extreme halophilic lipases research.

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Favaro, Yvette L., and Vincent C. Reinsborough. "Micellar catalysis in mixed anionic/cationic surfactant systems." Canadian Journal of Chemistry 72, no. 12 (December 1, 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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Tee, Oswald S., and Alexei A. Fedortchenko. "Transition state stabilization by micelles: the hydrolysis of p-nitrophenyl alkanoates in cetyltrimethylammonium bromide micelles." Canadian Journal of Chemistry 75, no. 10 (October 1, 1997): 1434–38. http://dx.doi.org/10.1139/v97-172.

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The cleavage of p-nitrophenyl alkanoates (acetate to octanoate) at high pH is modestly catalyzed by micelles formed from cetyltrimethylammonium bromide (CTAB) in aqueous solution. Rate constants exhibit saturation behaviour with respect to [CTAB], consistent with substrate binding in the micelles. The strength of substrate binding and transition state binding to the micelles increases monotonically with the acyl chain length, and with exactly the same sensitivity. As a result, the extent of acceleration (or catalytic ratio) is independent of the ester chain. These and earlier results are consistent with the reaction centre being located in the Stern layer of the micelle, with the acyl chain of the ester being directed into the hydrophobic micellar interior. The chain length dependence of kinetic parameters found in this work is comparable to that found previously for ester cleavage by cyclodextrins and by various enzymes with hydrophobic binding sites, as well as to that observed for other phenomena involving hydrophobic effects. Keywords: catalysis, ester hydrolysis, micelles, transition state.

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Stadlbauer, John M., Krishnan Venkateswaran, Hugh A. Gillis, Gerald B. Porter, and David C. Walker. "Micelle-induced change of mechanism in the reaction of muonium with acetone." Canadian Journal of Chemistry 74, no. 11 (November 1, 1996): 1945–51. http://dx.doi.org/10.1139/v96-221.

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Muonium atoms add to the O atom of the carbonyl group of acetone to give the muonated free radical (CH3)2Ċ-O-Mu when the reaction takes place in water or hydrocarbons, but not when the acetone is localized in micelles. Micelles have no effect on the formation of muonated cyclohexadienyl radicals when muonium reacts with benzene under similar conditions. The addition reaction with acetone appears to have been subsumed by a faster alternative reaction in the micellar environment. Evidence is presented for this interpretation rather than for an inhibition of the radical or for a shift in the muon level-crossing resonance spectrum with hydrogen (muonium) bonding, though major shifts are seen for the spectrum of this radical in pure solvents of widely different dielectric constant. It is suggested that muonium's "abstraction" reaction takes over in micelles because significant micelle-induced enhancement effects were previously observed in that type of reaction. The data are consistent with a rate constant for the abstraction reaction of muonium with acetone in micelles of >6 × 108 M−1 s−1. Key words: muonium, kinetic isotope effects, micelle enhancement, H/Mu-addition, H/Mu abstraction.

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34

ul Haq, Naveed, Muhammad Usman, Ajaz Hussain, Zahoor Hussain Farooqi, Muhammad Saeed, Sadia Hanif, Muhammad Irfan, Mohammad Siddiq, and Usman Ali Rana. "Partitioning of reactive yellow 86 between aqueous and micellar media studied by differential absorption spectroscopy." Canadian Journal of Chemistry 95, no. 6 (June 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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Procházka, Karel, Hélène Delcros, and Geneviève Delmas. "A light scattering and calorimetric study of micelle formation by a polystyrene -b-hydrogenated polyisoprene block copolymer in a binary solvent (pentane–cyclopentane)." Canadian Journal of Chemistry 66, no. 4 (April 1, 1988): 915–18. http://dx.doi.org/10.1139/v88-155.

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A light scattering and calorimetric study was made of micelle formation by a polystyrene-b-hydrogenated polyisoprene in a binary mixture. The polymer 0.42 weight percent PS, is unassociated in cyclopentane (c-C5) but forms micelles with a PS core in n-pentane, a non-solvent for PS. Light scattering measurements and heats of mixing, obtained over the binary composition range at a polymer concentration higher than the c.m.c., show that the solution changes from the unassociated to the micellar state for solutions richer in pentane than 0.4 volume fraction. Using heats of mixing of the corresponding homopolymers, the heat of micellization is found to be −5.1 + 0.3 J g−1, a value which supports the model of an enthalpy driven process of micellization.

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Akbar, Javed R., Rubena Deubry, D. Gerrard Marangoni, and Shawn D. Wettig. "Interactions between gemini and nonionic pharmaceutical surfactants." Canadian Journal of Chemistry 88, no. 12 (December 2010): 1262–70. http://dx.doi.org/10.1139/v10-135.

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The nature and strength of the interactions between the 1,3-bis(dimethylhexadecyl)propanediammonium dibromide (16-3-16) gemini surfactant and a homologous series of nonionic polyoxyethylene (20) sorbitan ester surfactants having laurate (Tween 20), stearate (Tween 60), or oleate (Tween 80) alkyl tails has been investigated. The critical micelle concentration (cmc) values of the mixed gemini–tween systems were determined using the du Noüy ring surface tension method, and the results have been analyzed using Clint’s, Rubingh’s, Motomura’s, and Maeda’s theories for mixed micellar systems. The results demonstrate a synergistic mixing behaviour between the Tween surfactants and the 16-3-16 gemini surfactant, where the strength of interaction is dependent upon the chain length and saturation of the Tween alkyl tail.

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Lorenzetto, Tommaso, Giacomo Berton, Fabrizio Fabris, and Alessandro Scarso. "Recent designer surfactants for catalysis in water." Catalysis Science & Technology 10, no. 14 (2020): 4492–502. http://dx.doi.org/10.1039/d0cy01062f.

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Recent development of new designer surfactants further spurs the development of micellar catalysis in water for chemical transformations and catalysis, providing reliable alternatives to the employment of organic solvents.

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38

Dahadha, Adnan A., Mohammed Hassan, Tamara Mfarej, Razan Bani Issa, Mohamed J. Saadh, Mohammad Al-Dhoun, Mohammad Abunuwar, and 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 (July 1, 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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39

Khan, Mohammad Niyaz, and Ibrahim Isah Fagge. "Kinetics and Mechanism of Cationic Micelle/Flexible Nanoparticle Catalysis: A Review." Progress in Reaction Kinetics and Mechanism 43, no. 1 (March 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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40

Bunton, Clifford A., Houshang J. Foroudian, Nicholas D. Gillitt, and Christy R. Whiddon. "Dephosphorylation and aromatic nucleophilic substitution in nonionic micelles. The importance of substrate location." Canadian Journal of Chemistry 76, no. 6 (June 1, 1998): 946–54. http://dx.doi.org/10.1139/v98-093.

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Reactions of OH- and F- with p-nitrophenyl diphenyl phosphate (pNPDPP) are inhibited by very dilute dodecyl (10) and (23) polyoxyethylene glycol (C12E10 and C12E23, respectively), but rate constants become independent of surfactant concentrations at concentrations above the critical micelle concentration. Low charge density anions, e.g., ClO4-, inhibit and low charge density cations, e.g., (n-C7H15)4N+, accelerate reactions, probably by controlling concentrations of nucleophiles in the palisade layer. Diphenyl phosphorofluoridate, generated by attack of F-, is not detected but is rapidly hydrolyzed to phenyl phosphorofluoridate or diphenyl phosphate ion with loss of phenol or F-. The products are different in DMSO containing modest amounts (<15 vol%) of water and no surfactant and are phenyl phosphorofluoridate and difluorophosphate ions generated by attack of F- on the initial phosphorofluoridate. These differences are consistent with the micellar palisade layer being water-rich. Although the nonionic surfactants do not intervene nucleophilically in reactions of pNPDPP, considerable amounts of ether are formed in the reaction of 2,4-dinitrochlorobenzene (DNCB), in C12E10 and C12E23 at high pH by attack of alkoxide ion with the relatively hydrophilic DNCB located close to the micellar surface. The differences in the chemistries of reactions of pNPDPP and DNCB appear to be associated largely with differences in locations of these substrates in the nonionic micelles.Key words: fluoridates, p-nitrophenyl diphenyl phosphate, 2,4-dinitrochlorobenzene, nonionic micelles, palisade layer.

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Huang, Xin, Zeyuan Dong, Junqiu Liu, Shizhong Mao, Jiayun Xu, Guimin Luo, and Jiacong Shen. "Selenium-Mediated Micellar Catalyst: An Efficient Enzyme Model for Glutathione Peroxidase-like Catalysis." Langmuir 23, no. 3 (January 2007): 1518–22. http://dx.doi.org/10.1021/la061727p.

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42

Hils, Christian, Ian Manners, Judith Schöbel, and Holger Schmalz. "Patchy Micelles with a Crystalline Core: Self-Assembly Concepts, Properties, and Applications." Polymers 13, no. 9 (May 4, 2021): 1481. http://dx.doi.org/10.3390/polym13091481.

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Crystallization-driven self-assembly (CDSA) of block copolymers bearing one crystallizable block has emerged to be a powerful and highly relevant method for the production of one- and two-dimensional micellar assemblies with controlled length, shape, and corona chemistries. This gives access to a multitude of potential applications, from hierarchical self-assembly to complex superstructures, catalysis, sensing, nanomedicine, nanoelectronics, and surface functionalization. Related to these applications, patchy crystalline-core micelles, with their unique, nanometer-sized, alternating corona segmentation, are highly interesting, as this feature provides striking advantages concerning interfacial activity, functionalization, and confinement effects. Hence, this review aims to provide an overview of the current state of the art with respect to self-assembly concepts, properties, and applications of patchy micelles with crystalline cores formed by CDSA. We have also included a more general discussion on the CDSA process and highlight block-type co-micelles as a special type of patchy micelle, due to similarities of the corona structure if the size of the blocks is well below 100 nm.

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43

Cruz Barrios, Eliandreina, Kyra V. Penino, and Onofrio Annunziata. "Diffusiophoresis of a Nonionic Micelle in Salt Gradients; Roles of Preferential Hydration and Salt-Induced Surfactant Aggregation." International Journal of Molecular Sciences 23, no. 22 (November 8, 2022): 13710. http://dx.doi.org/10.3390/ijms232213710.

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Diffusiophoresis is the migration of a colloidal particle in water driven by concentration gradients of cosolutes such as salts. We have experimentally characterized the diffusiophoresis of tyloxapol micelles in the presence of MgSO4, a strong salting-out agent. Specifically, we determined the multicomponent-diffusion coefficients using Rayleigh interferometry, cloud points, and dynamic-light-scattering diffusion coefficients on the ternary tyloxapol–MgSO4–water system at 25 °C. Our experimental results show that micelle diffusiophoresis occurs from a high to a low salt concentration (positive diffusiophoresis). Moreover, our data were used to characterize the effect of salt concentration on micelle size and salt osmotic diffusion, which occurs from a high to a low surfactant concentration. Although micelle diffusiophoresis can be attributed to the preferential hydration of the polyethylene glycol surface groups, salting-out salts also promote an increase in the size of micellar aggregates, ultimately leading to phase separation at high salt concentration. This complicates diffusiophoresis description, as it is not clear how salt-induced surfactant aggregation contributes to micelle diffusiophoresis. We, therefore, developed a two-state aggregation model that successfully describes the observed effect of salt concentration on the size of tyloxapol micelles, in the case of MgSO4 and the previously reported case of Na2SO4. Our model was then used to theoretically evaluate the contribution of salt-induced aggregation to diffusiophoresis. Our analysis indicates that salt-induced aggregation promotes micelle diffusiophoresis from a low to a high salt concentration (negative diffusiophoresis). However, we also determined that this mechanism marginally contributes to overall diffusiophoresis, implying that preferential hydration is the main mechanism causing micelle diffusiophoresis. Our results suggest that sulfate salts may be exploited to induce the diffusiophoresis of PEG-functionalized particles such as micelles, with potential applications to microfluidics, enhanced oil recovery, and controlled-release technologies.

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Migliorini, Francesca, Filippo Dei, Massimo Calamante, Samuele Maramai, and Elena Petricci. "Micellar Catalysis for Sustainable Hydroformylation." ChemCatChem 13, no. 12 (May 5, 2021): 2794–806. http://dx.doi.org/10.1002/cctc.202100181.

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45

Romsted, Laurence S., Clifford A. Bunton, and Jihu Yao. "Micellar catalysis, a useful misnomer." Current Opinion in Colloid & Interface Science 2, no. 6 (December 1997): 622–28. http://dx.doi.org/10.1016/s1359-0294(97)80055-6.

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46

Minkler, Stefan R. K., Bruce H. Lipshutz, and Norbert Krause. "Gold Catalysis in Micellar Systems." Angewandte Chemie 123, no. 34 (July 1, 2011): 7966–69. http://dx.doi.org/10.1002/ange.201101396.

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47

van den Broeke, L. J. P., V. G. de Bruijn, J. H. M. Heijnen, and J. T. F. Keurentjes. "Micellar Catalysis for Epoxidation Reactions." Industrial & Engineering Chemistry Research 40, no. 23 (November 2001): 5240–45. http://dx.doi.org/10.1021/ie001079j.

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48

Berndt, D. C., M. E. Ayoub, and M. H. Akhavan-Tafti. "Micellar catalysis by perfluorooctanoic acid." International Journal of Chemical Kinetics 19, no. 6 (June 1987): 513–18. http://dx.doi.org/10.1002/kin.550190604.

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Minkler, Stefan R. K., Bruce H. Lipshutz, and Norbert Krause. "Gold Catalysis in Micellar Systems." Angewandte Chemie International Edition 50, no. 34 (July 1, 2011): 7820–23. http://dx.doi.org/10.1002/anie.201101396.

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50

Broxton, Trevor J., John R. Christie, and Roland P. T. Chung. "Micellar catalysis of organic reactions. 23. Effect of micellar orientation of the substrate on the magnitude of micellar catalysis." Journal of Organic Chemistry 53, no. 13 (June 1988): 3081–84. http://dx.doi.org/10.1021/jo00248a032.

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Journal articles on the topic 'Catalisi micellare'

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