Effect of Urea on the Thermodynamics of Hexadecyltrimethylammonium Bromide Micelle Formation in Aqueous Solutions

Velikov, A. A.

doi:10.1134/s0036024418020255

Cited by 2 publications

(1 citation statement)

References 14 publications

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“…Thus, replacing water with urea and these two urea derivatives seems to have no appreciable effect on interactions between the surfactant molecules. We note that for more weakly associating systems, which are on the balance of association, urea is well-known to have significant effects, such as the micelle formation of relatively polar surfactants, or the self-assembly of DNA (into the double helix) or cellulose [ 12 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ].…”

Section: Resultsmentioning

confidence: 99%

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

2021

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Double-chain amphiphilic compounds, including surfactants and lipids, have broad significance in applications like personal care and biology. A study on the phase structures and their transitions focusing on dioctadecyldimethylammonium chloride (DODAC), used inter alia in hair conditioners, is presented. The phase behaviour is dominated by two bilayer lamellar phases, Lβ and Lα, with “solid” and “melted” alkyl chains, respectively. In particular, the study is focused on the effect of additives of different polarity on the phase transitions and structures. The main techniques used for investigation were differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS and WAXS). From the WAXS reflections, the distance between the alkyl chains in the bilayers was obtained, and from SAXS, the thicknesses of the surfactant and water layers. The Lα phase was found to have a bilayer structure, generally found for most surfactants; a Lβ phase made up of bilayers with considerable chain tilting and interdigitation was also identified. Depending mainly on the polarity of the additives, their effects on the phase stabilities and structure vary. Compounds like urea have no significant effect, while fatty acids and fatty alcohols have significant effects, but which are quite different depending on the nonpolar part. In most cases, Lβ and Lα phases exist over wide composition ranges; certain additives induce transitions to other phases, which include cubic, reversed hexagonal liquid crystals and bicontinuous liquid phases. For a system containing additives, which induce a significant lowering of the Lβ–Lα transition, we identified the possibility of a triggered phase transition via dilution with water.

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Section: Resultsmentioning

confidence: 99%

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

2021

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Hydrophobic interactions control the self-assembly of DNA and cellulose

Lindman

Medronho

Alves

et al. 2021

Quart. Rev. Biophys.

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Desoxyribosenucleic acid, DNA, and cellulose molecules self-assemble in aqueous systems. This aggregation is the basis of the important functions of these biological macromolecules. Both DNA and cellulose have significant polar and nonpolar parts and there is a delicate balance between hydrophilic and hydrophobic interactions. The hydrophilic interactions related to net charges have been thoroughly studied and are well understood. On the other hand, the detailed roles of hydrogen bonding and hydrophobic interactions have remained controversial. It is found that the contributions of hydrophobic interactions in driving important processes, like the double-helix formation of DNA and the aqueous dissolution of cellulose, are dominating whereas the net contribution from hydrogen bonding is small. In reviewing the roles of different interactions for DNA and cellulose it is useful to compare with the self-assembly features of surfactants, the simplest case of amphiphilic molecules. Pertinent information on the amphiphilic character of cellulose and DNA can be obtained from the association with surfactants, as well as on modifying the hydrophobic interactions by additives.

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Effect of Urea on the Thermodynamics of Hexadecyltrimethylammonium Bromide Micelle Formation in Aqueous Solutions

Cited by 2 publications

References 14 publications

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects

Hydrophobic interactions control the self-assembly of DNA and cellulose

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