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Title: Double-chain cationic surfactants: swelling, structure, phase transitions and additive effects
Authors: Gonçalves, Rui A.
Lam, Yeng Ming
Lindman, Björn
Keywords: Engineering::Materials
Issue Date: 2021
Source: Gonçalves, R. A., Lam, Y. M. & Lindman, B. (2021). Double-chain cationic surfactants: swelling, structure, phase transitions and additive effects. Molecules, 26(13), 3946-.
Project: APG2013/016 
Journal: Molecules 
Abstract: 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.
ISSN: 1420-3049
DOI: 10.3390/molecules26133946
Schools: School of Materials Science and Engineering 
Rights: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MSE Journal Articles

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