Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements

Cutler, S. G.; Meares, P.; Hall, Denver G.

doi:10.1039/f19787401758

Cited by 118 publications

(77 citation statements)

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“…4 (circles), remains close to zero up to the CMC and then increases linearly with added lipid shortly thereafter. Electrode measurements with anionic surfactants have revealed that the monomer activity begins to decrease with increasing surfactant concentration above the CMC, because of the increasing micelle concentration (12)(13)(14). If this also happens with (8:0) 2 PG, it does not appear to be associated with an appreciable heat evolution or absorption (see Fig.…”

Section: Thermodynamics Of Demicellizationmentioning

confidence: 90%

Thermodynamics of Phospholipid Self-Assembly

Marsh

2012

Biophysical Journal

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Negatively charged phospholipids are an important component of biological membranes. The thermodynamic parameters governing self-assembly of anionic phospholipids are deduced here from isothermal titration calorimetry. Heats of demicellization were determined for dioctanoyl phosphatidylglycerol (PG) and phosphatidylserine (PS) at different ionic strengths, and for dioctanoyl phosphatidic acid at different pH values. The large heat capacity (ΔC°(P) ∼ -400 J.mol(-1) K(-1) for PG and PS), and zero enthalpy at a characteristic temperature near the physiological range (T(∗) ~ 300 K for PG and PS), demonstrate that the driving force for self-assembly is the hydrophobic effect. The pH and ionic-strength dependences indicate that the principal electrostatic contribution to self-assembly comes from the entropy associated with the electrostatic double layer, in agreement with theoretical predictions. These measurements help define the thermodynamic effects of anionic lipids on biomembrane stability.

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Section: Thermodynamics Of Demicellizationmentioning

confidence: 90%

Thermodynamics of Phospholipid Self-Assembly

Marsh

2012

Biophysical Journal

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“…The first becomes larger and larger and at a higher rate with a decreasing value of ␤ (␤ Ͻ 1). So, the relation [5] can be written as…”

Section: Figmentioning

confidence: 99%

“…Electromotive force (EMF) measurements usually allow access, on the one hand, to one of the main typical features of ionic micelles, the effective association rate ␤, and on the other hand, to interesting information comparing EMF measurements with amphiphile and counterion-selective electrodes (1,2,5,8,(13)(14)(15). By means of the electrochemical method (16 -18) the determination of the ␤ value for different surfactants and counterions is now accurate and reliable.…”

Section: Introductionmentioning

confidence: 99%

Counterion Effects in Aqueous Solutions of Cationic Surfactants: Electromotive Force Measurements and Thermodynamic Model

Gaillon

Lelièvre

Gaboriaud

1999

Journal of Colloid and Interface Science

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“…Free energies of micellar systems can readily be measured from colligative properties (7,9) or from electromotive forces (29)(30)(31). Then, from the experimental free energies and enthalpies, the partial molal entropies of the surfactant solutions can also be calculated as a function of concentration (6).…”

Section: = (+Cm)/mmentioning

confidence: 99%

Thermochemistry of aqueous micellar systems

Desnoyers¹,

DeLisi²,

Perron³

1980

Pure and Applied Chemistry

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-Surfactants tend to aggregate above a certain concentration, called the critical micelle concentration, into large clusters or micelles. With modern calorimetric and other related techniques it is now possible to measure precisely and rapidly the thermodynamic properties of liquid systems over a wide range of concentration and temperature. An overview is given of data obtained in our laboratory for heat capacities, enthalpies, entropies and free energies of aqueous sodium decanoate, octylammonium hydrobromide, nonyl and decyltrimethylammonium bromide. The thermodynamic functions of micellization are derived and interpreted with a phase-separation model. The closely related microemulsions are also briefly discussed. INTRODUCTIONMicellar systems are very special types of macromolecular solutions. Arnphiphilic molecules or ions tend to aggregate in solution into units which are comparable in size to biocolloids, and their properties can be studied with many of the standard techniques that are used for other types of macromolecules (1-5). They differ however in their stability. They form only above concentrations that are called critical micelle concentrations (CMC), and the aggregates, known as micelles, are in dynamic equilibrium with the singly-dispersed solute in the system. The investigation of thermodynamic properties of surfactants are primarily concerned with the study of various factors affecting this equilibrium.The most common way of investigating the thermodynamics of micellar systems is to determine the changes in the CMC with temperature or in the presence of various additives or cosolvents. This is done through measurement of a property, such as conductance or surface tension, which shows a break in the micellization region. This approach is limited since the CMC is not always sharply defined, very high precision is required to extract.the changes in heats and in heat capacities during micellization, there is no easy way of knowing if the observed changes are due to modification in properties of the singly-dispersed molecules, micellar units or both, and oversimplified models for micellization have to be used.In the last ten years or so (6-11) we have undertaken very systematic studies of the direct measurement of thermodynamic properties of surfactants in water. Our aim was to measure all thermodynamic properties of well-characterized surfactants, over a wide range of concentration covering the pre and postmicellar regions, in order to predict the temperature and pressure dependence of various equilibrium properties and to test rigorously the main models and theories of micellization. EXPERIMENTALThis paper is concerned with the thermochemical properties of aqueous surfactants. It is sufficient to mention that the heats of dilution and heat capacities per unit volume were measured with commercial versions (SQDEV INC) of flow microcalorimeters that have been welldescribed in the literature (12)(13)(14). For heat capacities, simultaneous determination of densities are required, and these were...

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Ionic activities in sodium dodecyl sulphate solutions from electromotive force measurements

Cited by 118 publications

References 0 publications

Thermodynamics of Phospholipid Self-Assembly

Thermodynamics of Phospholipid Self-Assembly

Counterion Effects in Aqueous Solutions of Cationic Surfactants: Electromotive Force Measurements and Thermodynamic Model

Thermochemistry of aqueous micellar systems

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