Correction. The Aqueous Phase Behavior of Surfactants

Laughlin, Robert G.

doi:10.1021/ja00147a600

Cited by 308 publications

(474 citation statements)

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“…10,17,22,23 The reason the transition to the micellar phase is not seen in the sorption calorimetric experiments is the combination of two factors. The first factor is the high water activity.…”

Section: Resultsmentioning

confidence: 99%

Hydration of Dimethyldodecylamine-N-oxide: Enthalpy and Entropy Driven Processes

Kocherbitov

Söderman

2006

J. Phys. Chem. B

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Dimethyldodecylamine-N-oxide (DDAO) has only one polar atom that is able to interact with water. Still, this surfactant shows very hydrophilic properties: in mixtures with water, it forms normal liquid crystalline phases and micelles. Moreover, there is data in the literature indicating that the hydration of this surfactant is driven by enthalpy while other studies show that hydration of surfactants and lipids typically is driven by entropy. Sorption calorimetry allows resolving enthalpic and entropic contributions to the free energy of hydration at constant temperature and thus directly determines the driving forces of hydration. The results of the present sorption calorimetric study show that the hydration of liquid crystalline phases of DDAO is driven by entropy, except for the hydration of the liquid crystalline lamellar phase which is co-driven by enthalpy. The exothermic heat effect of the hydration of the lamellar phase arises from formation of strong hydrogen bonds between DDAO and water. Another issue is the driving forces of the phase transitions caused by the hydration. The sorption calorimetric results show that the transitions from the lamellar to cubic and from the cubic to the hexagonal phase are driven by enthalpy. Transitions from solid phases to the liquid crystalline lamellar phase are entropically driven, while the formation of the monohydrate from the dry surfactant is driven by enthalpy. The driving forces of the transition from the hexagonal phase to the isotropic solution are close to zero. These sorption calorimetric results are in good agreement with the analysis of the binary phase diagram based on the van der Waals differential equation. The phase diagram of the DDAO-water system determined using DSC and sorption calorimetry is presented.

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Section: Resultsmentioning

confidence: 99%

Hydration of Dimethyldodecylamine-N-oxide: Enthalpy and Entropy Driven Processes

Kocherbitov

Söderman

2006

J. Phys. Chem. B

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“…The hexagonal phase is made up of cylindrical micelles. Lamellar phases also occur in a wide range of concentrations, just like hexagonal phases, but at higher concentrations [44]. The characteristic feature is a reduction in viscosity in comparison with the hexagonal phase and that is also an indirect proof of their presence.…”

Section: Lyotropic Liquid Crystalsmentioning

confidence: 98%

“…The values of the critical micelle concentration (CMC) are about 0.24 wt% (SLS) and 0.11 wt% (ESLS) [7,[44][45][46][47][48][49][50]. These results are unexpected as the hydrophilic part in the ESLS molecule is expanded by addition of two molecules of ethylene oxide which should increase water solubility and ''shift'' the CMC value towards higher concentrations.…”

Section: Micellar Solutions Of Alkyl Sulfatesmentioning

confidence: 98%

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The Effect of Concentration on Lubricating Properties of Aqueous Solutions of Sodium Lauryl Sulfate and Ethoxylated Sodium Lauryl Sulfate

2010

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The objective of this study was to formulate new ecological lubricating substances, primarily water-based, and to verify their tribological and physicochemical properties. Initially, simple binary solutions were investigated. Then, various additives were added depending on application targets. Two alkyl sulfates were selected as additives modifying lubricating properties of water: sodium lauryl sulfate (SLS) and ethoxylated sodium lauryl sulfate (ESLS). They have an identical hydrophobic part in the form of an alkyl chain consisting of 12 carbon atoms. The SO 4 2-anion forms the hydrophilic part in SLS molecules, whereas an ESLS molecule also contains two mers of ethylene oxide which cause an increase in its hydrophilicity relative to SLS. Both SLS and ESLS exhibit high surface activity measured by their surface tension. Micelles form in aqueous solutions of alkyl sulfates at low concentrations of the order of 1%, whereas the presence of liquid crystalline phases can be found at the concentrations of 40 and 70%. High surface activity and formation of structures in the solutions (micelles, mesophases) formed the basis for application of the compounds as additives modifying lubricating properties. Tribological properties of aqueous solutions of alkyl sulfates were verified with a four-ball machine (T02 tester) at a constant load of 2 kN. The values of friction coefficient (l) were a measure of motion resistance, while the wear scar diameter (d) was a measure of wear. Alkyl sulfates significantly improve tribological properties of water. The coefficient of friction decreased sixfold and the wear scar diameter decreased by as much as twofold relative to the base. Non-monotonic changes in the tribological properties measured were observed as a function of concentration of additives. An attempt was made to relate those atypical changes with the presence of micelles and mesophases in both the surface phase and the bulk phase. In the model proposed the whole concentration range was divided into four areas in which tribological properties correspond well with physicochemical properties, particularly with the structures formed in solutions and at the interface.

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“…Depending on the balance between the polar and nonpolar parts, a large number of self-assembly structures is (43)(44)(45). Only recently have we started to learn about how polymers modify surfactant self-assembly structures (2,3,9,46).…”

Section: The Structure Of Dna-surfactant Complexes Is Importantmentioning

confidence: 99%

DNA-lipid systems: A physical chemistry study

Dias

Antunes

Miguel

et al. 2002

Braz J Med Biol Res

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It is well known that the interaction of polyelectrolytes with oppositely charged surfactants leads to an associative phase separation; however, the phase behavior of DNA and oppositely charged surfactants is more strongly associative than observed in other systems. A precipitate is formed with very low amounts of surfactant and DNA. DNA compaction is a general phenomenon in the presence of multivalent ions and positively charged surfaces; because of the high charge density there are strong attractive ion correlation effects. Techniques like phase diagram determinations, fluorescence microscopy, and ellipsometry were used to study these systems. The interaction between DNA and catanionic mixtures (i.e., mixtures of cationic and anionic surfactants) was also investigated. We observed that DNA compacts and adsorbs onto the surface of positively charged vesicles, and that the addition of an anionic surfactant can release DNA back into solution from a compact globular complex between DNA and the cationic surfactant. Finally, DNA interactions with polycations, chitosans with different chain lengths, were studied by fluorescence microscopy, in vivo transfection assays and cryogenic transmission electron microscopy. The general conclusion is that a chitosan effective in promoting compaction is also efficient in transfection.

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Correction. The Aqueous Phase Behavior of Surfactants

Cited by 308 publications

References 0 publications

Hydration of Dimethyldodecylamine-N-oxide: Enthalpy and Entropy Driven Processes

Hydration of Dimethyldodecylamine-N-oxide: Enthalpy and Entropy Driven Processes

The Effect of Concentration on Lubricating Properties of Aqueous Solutions of Sodium Lauryl Sulfate and Ethoxylated Sodium Lauryl Sulfate

DNA-lipid systems: A physical chemistry study

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