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Daniel Blankschtein - One of the best experts on this subject based on the ideXlab platform.
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prediction of conformational characteristics and Micellar Solution properties of fluorocarbon surfactants
Langmuir, 2005Co-Authors: Vibha Srinivasan, Daniel BlankschteinAbstract:A molecular-thermodynamic theory is developed to model the micellization of fluorocarbon surfactants in aqueous Solutions, by combining a molecular model that evaluates the free energy of micellization of fluorocarbon surfactant micelles with a previously developed thermodynamic framework describing the free energy of the Micellar Solution. In the molecular model of micellization developed, a single-chain mean-field theory is combined with an appropriate rotational isomeric state model of fluorocarbon chains to describe the packing of the fluorocarbon surfactant tails inside the micelle core. Utilizing this single-chain mean-field theory, the packing free energies of fluorocarbon surfactants are evaluated and compared with those of their hydrocarbon analogues. We find that the greater rigidity of the fluorocarbon chain promotes its packing in Micellar aggregates of low curvatures, such as bilayers. In addition, the mean-field approach is utilized to predict the average conformational characteristics (specifically, the bond order parameters) of fluorocarbon and hydrocarbon surfactant tails within the micelle core, and the predictions are found to agree well with the available experimental results. The electrostatic effects in fluorocarbon ionic surfactant micelles are modeled by allowing for counterion binding onto the charged micelle surface, which accounts explicitly for the effect of the counterion type on the Micellar Solution properties. In addition, a theoretical formulation is developed to evaluate the free energy of micellization and the size distribution of finite disklike micelles, which often form in the case of fluorocarbon surfactants. We find that, compared to their hydrocarbon analogues, fluorocarbon surfactants exhibit a greater tendency to form cylindrical or disklike micelles, as a result of their larger molecular volume as well as due to the greater conformational rigidity of the fluorocarbon tails. The molecular-thermodynamic theory developed is then applied to several ionic fluorocarbon surfactant-electrolyte systems, including perfluoroalkanoates and perfluorosulfonates with added LiCl or NH(4)Cl, and various Micellar Solution properties, including critical micelle concentrations (cmc's), optimal micelle shapes, and average micelle aggregation numbers, are predicted. The predicted Micellar Solution properties agree reasonably well with the available experimental results.
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effect of counterion binding on Micellar Solution behavior 2 prediction of Micellar Solution properties of ionic surfactant electrolyte systems
Langmuir, 2003Co-Authors: Vibha Srinivasan And, Daniel BlankschteinAbstract:A molecular−thermodynamic theory of micellization of ionic surfactants, developed in paper 1 of this series, is applied here to specific ionic surfactant−electrolyte systems in order to test its ability to quantitatively predict various Micellar Solution properties, including the effect of the counterion hydrated size, valence, and lipophilicity. With this goal in mind, the theory is utilized to model surfactant Solutions containing (i) monovalent counterions (specifically, the alkali metal dodecyl sulfate series, MDS), (ii) multivalent counterions (specifically, the sodium dodecyl dioxyethylene sulfate surfactant, SDE2S, with added AlCl3 + NaCl and CaCl2 + NaCl), and (iii) organic counterions (specifically, the alkyl trimethylammonium salicylate series, CnTASal). The predicted Micellar Solution properties include (i) the optimal degree of binding of each counterion species onto the charged micelle surface, (ii) the surfactant critical micelle concentration, and (iii) the optimal micelle shape and average...
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effect of counterion binding on Micellar Solution behavior 1 molecular thermodynamic theory of micellization of ionic surfactants
Langmuir, 2003Co-Authors: Vibha Srinivasan And, Daniel BlankschteinAbstract:A molecular−thermodynamic theory is developed to model the micellization of ionic surfactants with added electrolytes in aqueous Solution, by combining a thermodynamic description of the Micellar Solution free energy with a molecular model of the micellization process. The molecular model of micellization, which accounts for the various free-energy contributions associated with assembling the charged micelle from its constituent surfactant ions, allows for a fraction of the counterions, released by the surfactant heads and/or any added electrolytes, to bind onto the micelle surface and effectively induce a partial reduction of the micelle surface charge. The bound counterions are modeled as being intercalated among the surfactant heads on the micelle surface of charge. The remaining counterions are distributed according to the Boltzmann equation in the diffuse region, which lies beyond the Stern layer of steric exclusion adjacent to the micelle surface of charge. Expressions for the various free-energy co...
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predicting Micellar Solution properties of binary surfactant mixtures
Langmuir, 1998Co-Authors: A Shiloach, Daniel BlankschteinAbstract:The widespread use of surfactant mixtures in practical surfactant applications motivates the need for a comprehensive predictive theory that will improve our fundamental understanding of the behavior of these complex systems and facilitate the design and optimization of new surfactant mixtures. With this in mind, we have combined a molecular model of mixed micellization with a thermodynamic framework to predict a broad spectrum of Solution properties of mixed surfactant systems. The molecular model accounts for Micellar mixing nonidealities resulting from electrostatic and steric interactions between the surfactant hydrophilic heads and from packing of surfactant hydrophobic tails of unequal lengths in the Micellar core. In particular, we describe in detail a rigorous treatment of electrostatic interactions that enables the theory to quantitatively predict properties for binary mixtures containing nonionic, anionic, cationic, and zwitterionic surfactants, including the critical micelle concentration (cmc)...
Andreas Mohr - One of the best experts on this subject based on the ideXlab platform.
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Nile red dye in aqueous surfactant and Micellar Solution.
Langmuir : the ACS journal of surfaces and colloids, 2015Co-Authors: Indah N. Kurniasih, Hua Liang, Parveen Choudhary Mohr, Gaurang Khot, Jürgen P. Rabe, Andreas MohrAbstract:The solubilization behavior of nile red dye in aqueous surfactant and Micellar Solutions was studied by optical spectroscopic techniques, dynamic light scattering, and atomic force microscopy. Nile...
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nile red dye in aqueous surfactant and Micellar Solution
Langmuir, 2015Co-Authors: Indah N. Kurniasih, Hua Liang, Parveen Choudhary Mohr, Gaurang Khot, Jürgen P. Rabe, Andreas MohrAbstract:The solubilization behavior of nile red dye in aqueous surfactant and Micellar Solutions was studied by optical spectroscopic techniques, dynamic light scattering, and atomic force microscopy. Nile red exhibits considerable absorption in the subMicellar concentration region. When dispersed in aqueous surfactant and/or Micellar Solution, nile red molecules tend to form nonemissive dimers and/or H-type aggregates through π-π stacking interactions. This phenomenon may limit the use of nile red in solubilization studies. In the presence of ionic SDS and CTAB micelles, the solubilization of nile red appears to take place primarily at the charged Micellar surface within the interfacial region. Similarly, spectra in Micellar Solution of nonionic Triton X-100 revealed that nile red dye penetrates the hydrophilic, interfacial poly(oxyethylene) region of the micelles but cannot reach the hydrophobic, innermost core. Our results therefore suggest that nile red dye must be chosen carefully when probing (Micellar) hydrophobic environments and (micro)domains.
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localization of hydrophobic n diazeniumdiolates in aqueous Micellar Solution
Langmuir, 2010Co-Authors: Parveen Choudhary Mohr, Andreas Mohr, Tommy Pozo Vila, Hansgert KorthAbstract:The interaction of phenyl-substituted zwitterionic N-diazeniumdiolates PhCH2N[N(O)NO]−(CH2)2NH3+ (1) and PhCH2N[N(O)NO]−(CH2)2NH2+CH2Ph (2) with aqueous Micellar Solutions of prototypal surfactants...
Xiancheng Zeng - One of the best experts on this subject based on the ideXlab platform.
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metalloMicellar catalysis hydrolysis of phosphate monoester and phosphodiester by cu ii zn ii complexes of pyridyl ligands in ctab Micellar Solution
Journal of Colloid and Interface Science, 2006Co-Authors: Fubin Jiang, Liya Huang, Xiangguang Meng, Yufen Zhao, Xiancheng ZengAbstract:The catalytic hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) and p-nitrophenyl phosphate (NPP) by metallomicelles composed of Cu(II) or Zn(II) complexes of bispyridine-containing alkanol ligands in CTAB Micellar Solution was investigated at 30 degrees C. The experimental results indicate that the complexes with a 1:1 ratio of ligands to metal ions for ligands 1 (1,7-bis(6-hydroxymethyl-2-pyridyl)-2,6-dioxaheptane) and 3 (1,4-bis[(6-hydroxymethyl-2-pyridyl)-2-oxapropyl]benzene) and a 1:2 ratio of ligands to metal ions for ligand 2 (1,14-bis(6-hydroxymethyl-2-pyridyl)-2,13-dioxatetradecane) in CATB Micellar Solution are the active species for the catalytic hydrolysis of BNPP and NPP, respectively. The ternary complex kinetic model for metalloMicellar catalysis was employed to obtain the relative kinetic and thermodynamic parameters, which demonstrated the catalytic mechanism for the hydrolysis of BNPP and NPP by metallomicelles.
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metalloMicellar catalysis hydrolysis of phosphate monoester by cu ii zn ii ni ii and co ii complexes of pyridyl ligands in ctab Micellar Solution
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Fubin Jiang, Xiangguang Meng, Bingying Jiang, Yangshu Cao, Xiancheng ZengAbstract:The hydrolysis of (p-nitrophenyl)phosphate (NPP) catalyzed by the Cu(II), Zn(II), Ni(II) and Co(II) complexes of lipophilic pyridine-containing alkanol ligands were investigated in the presence of an inert surfactant (CTAB). The experimental results indicate that 2:1 ligand:metal ion complexes in CTAB Micellar Solution are the active species for the catalytic hydrolysis of NPP. The ternary complex kinetic model for metalloMicellar catalysis was employed to treat with the results, so as to obtain the relative kinetic and thermodynamic parameters. The results predicted the reasonability of such kinetic models.
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catalytic hydrolysis of carboxylic acid esters by cu ii and zn ii complexes containing a tetracoordinate macrocyclic schiff base ligand in brij35 Micellar Solution
Journal of Molecular Catalysis A-chemical, 2004Co-Authors: Xingming Kou, Siqing Cheng, Xiancheng ZengAbstract:Abstract The macrocyclic Schiff base complexes of Cu(II) and Zn(II) in Brij35 Micellar Solution are investigated kinetically for the catalytic hydrolysis of p -nitrophenyl acetate (PNPA) and p -nitrophenyl picolinate (PNPP) at 30 °C. The results indicate that different mechanisms are operative for the two complexes in the hydrolysis of PNPA and PNPP. The Cu(II) complex can only catalyze the hydrolysis of PNPP by the mechanism which involves the nucleophilic attack of external hydroxide ion on the carbonyl, while the Zn(II) complex can accelerate the hydrolysis of both PNPP and PNPA, by way of the intramolecular nucleophilic attack of zinc-bound hydroxide ion on carbonyl for PNPP and the less effective intermolecular nucleophilic attack of zinc-bound hydroxide ion on carbonyl for PNPA, respectively. The catalytic activity of Zn(II) complex is close to or even higher than that of Cu(II) complex. The reason is discussed in details.
Rama Kant - One of the best experts on this subject based on the ideXlab platform.
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electrochromic response of nanostructured poly 3 4 ethylenedioxythiophene films grown in an aqueous Micellar Solution
Macromolecular Chemistry and Physics, 2008Co-Authors: Melepurath Deepa, Shweta Bhandari, Manju Arora, Rama KantAbstract:Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been electropolymerized from an aqueous Micellar Solution encompassing the monomer (EDOT) and the moieties sodium dodecyl sulfate (SDS) and lithium triflate. The presence of these anionic dopants in the polymer matrix and a doping level of 0.26 have been confirmed by X-ray photoemission and electron paramagnetic resonance (EPR) spectroscopy. The hydrophobic Micellar core encompassing the monomer orchestrates the growth of a uniform homogeneous polymer deposit as electron microscopy and atomic force microscopy studies reveal the film to be composed of a continuous interlinked network of quasi-spherical grains (50–150 nm in dimensions) and pores alongwith a low surface roughness. The film exhibits a large coloration efficiency of 153 cm 2 · C −1 and a transmission modulation of 62% (λ = 632.8 nm), which are manifestations of the open ion-permeable morphology. The Q (inserted/extracted) ratio ranges between 1.2 and 1.4 when cycled back and forth between the clear and blue states 2 500 times, thereby affirming the suitability of these films for practical electrochromic smart windows.
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Redox behavior and optical response of nanostructured poly(3,4-ethylenedioxythiophene) films grown in a camphorsulfonic acid based Micellar Solution
Electrochimica Acta, 2008Co-Authors: Shweta Bhandari, Melepurath Deepa, Satya Vrat Singh, Govind Gupta, Rama KantAbstract:Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been electropolymerized from an aqueous Micellar Solution comprising camphorsulfonic acid (CSA), lithium trifluoromethanesulfonate (LiCF3SO3) and EDOT. The inclusion of the dopants CS− and CF3SO3− in the polymer structure and an unusually high doping level of 0.54 have been ascertained by the X-ray photoelectron spectroscopy. Transmission electron microscopy and atomic force microscopy studies show that the Micellar effect of CSA leads to a morphology wherein polymer particles link together to form elongated shapes and also endows the film with a surface roughness of 25–30 nm. These nanostructures permit a facile intercalation–deintercalation of anions in the film during redox cycling. Electrochemical impedance spectroscopy show that the charge transfer phenomenon at the PEDOT–electrolyte interface is dominant in the high frequency region and diffusion controlled ionic movement prevails in the low frequency regime. The use of these films as potential cathodes in electrochromic windows is rationalized not only on the basis of their high scalability and ease of processing but also due to their large coloration efficiency (123 cm2 C−1) and transmission modulation (50%) at a photopic wavelength of 550 nm. But further improvement in color-bleach kinetics and reproducibility of redox behavior is desirable to broaden their spectrum of utility.
Fubin Jiang - One of the best experts on this subject based on the ideXlab platform.
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metalloMicellar catalysis hydrolysis of phosphate monoester and phosphodiester by cu ii zn ii complexes of pyridyl ligands in ctab Micellar Solution
Journal of Colloid and Interface Science, 2006Co-Authors: Fubin Jiang, Liya Huang, Xiangguang Meng, Yufen Zhao, Xiancheng ZengAbstract:The catalytic hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) and p-nitrophenyl phosphate (NPP) by metallomicelles composed of Cu(II) or Zn(II) complexes of bispyridine-containing alkanol ligands in CTAB Micellar Solution was investigated at 30 degrees C. The experimental results indicate that the complexes with a 1:1 ratio of ligands to metal ions for ligands 1 (1,7-bis(6-hydroxymethyl-2-pyridyl)-2,6-dioxaheptane) and 3 (1,4-bis[(6-hydroxymethyl-2-pyridyl)-2-oxapropyl]benzene) and a 1:2 ratio of ligands to metal ions for ligand 2 (1,14-bis(6-hydroxymethyl-2-pyridyl)-2,13-dioxatetradecane) in CATB Micellar Solution are the active species for the catalytic hydrolysis of BNPP and NPP, respectively. The ternary complex kinetic model for metalloMicellar catalysis was employed to obtain the relative kinetic and thermodynamic parameters, which demonstrated the catalytic mechanism for the hydrolysis of BNPP and NPP by metallomicelles.
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metalloMicellar catalysis hydrolysis of phosphate monoester by cu ii zn ii ni ii and co ii complexes of pyridyl ligands in ctab Micellar Solution
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Fubin Jiang, Xiangguang Meng, Bingying Jiang, Yangshu Cao, Xiancheng ZengAbstract:The hydrolysis of (p-nitrophenyl)phosphate (NPP) catalyzed by the Cu(II), Zn(II), Ni(II) and Co(II) complexes of lipophilic pyridine-containing alkanol ligands were investigated in the presence of an inert surfactant (CTAB). The experimental results indicate that 2:1 ligand:metal ion complexes in CTAB Micellar Solution are the active species for the catalytic hydrolysis of NPP. The ternary complex kinetic model for metalloMicellar catalysis was employed to treat with the results, so as to obtain the relative kinetic and thermodynamic parameters. The results predicted the reasonability of such kinetic models.
