Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/137224
Title: Tunable and stable swollen surfactant lamellar phases for hair-care applications
Authors: Goncalves Cardoso, Rui Andre
Keywords: Engineering::Materials::Functional materials
Science::Chemistry::Physical chemistry::Surface chemistry
Issue Date: 2019
Publisher: Nanyang Technological University
Source: Goncalves Cardoso, R. A. (2019). Tunable and stable swollen surfactant lamellar phases for hair-care applications. Doctoral thesis, Nanyang Technological University, Singapore.
Abstract: Double-tailed surfactants have been commonly used in the formulation of personal-care products so as to provide some unique properties in the final product. These include the ability to deposit particles on surfaces and storage stability at ambient conditions. The challenge is to develop a single and stable lamellar gel (Lβ) phase to achieve maximum swelling without coexisting water phase. Hair-conditioner compositions are generally formulated with various active compounds, such as cationic surfactants and molecules with specific functionalities. The concentration of various compounds will give rise to formulation with a variety of microstructures which will in turn provide different desirable material properties. Therefore, it is important to have good understanding of the phase behavior of such formulations to improve the formulation of products for hair-care applications. The investigation on the effect of additives is performed on dioctadecyldimethylammonium chloride mainly. In this study, the thermal behavior, swelling behavior (in the presence of water), packing structure and deposition profile of double-tailed surfactant systems have been investigated. Initially, a phase study of dioctadecyldimethylammonium bromide (DODAB) and chloride (DODAC) in aqueous solution was conducted to determine the effect of the counterion on lamellar stability. Next, the effects of fifteen commonly used compounds, such as “ureas”, hydrotrope molecules and short and intermediate-chain fatty acids and alcohols on the lamellar stability and packing structure upon thermal changes were examined. The physical appearance of these surfactant systems was examined optically and with the use of cross-polarizers to enable a facile way to detect the formation of birefringent structures, manifested by the observation of Maltese cross or oily streak textures. Differential scanning calorimetry (DSC) was used to establish the main phase transition (often called gel-to-liquid crystalline, Lα-Lβ) temperature (Tm) and small/wide-angle X-ray scattering (SAXS and WAXS) was employed to determine the surfactant packing structure, polar and non-polar domain thickness and area per surfactant molecule below and above the Tm. Synchrotron SAXS and WAXS was used to determine the surfactant packing of diluted samples used for surfactant deposition investigation. In-situ null ellipsometry was used to monitor and characterize time-dependent surfactant film deposition on a surface with respect to the layer thickness and adsorbed amount of surfactant. The deposition was performed upon rinsing and presented and discussed as a function of sample composition and concentration. This Ph.D. work shows that stable Lα phases are yielded by incorporating small polar additives to the DODAC bilayer, thus lowering the Lα-Lβ phase transition temperature. These stable Lα phases can spontaneously be changed into the Lβ phase and subsequently deposited on a substrate. Ellipsometry studies demonstrate that dilution of the surfactant-additive-water phases leads to the deposition of well-defined robust layers onto silica. The adsorbed surfactant layers having approximately the same thickness of the surfactant chain length, are stable and are not affected by extensive dilution.
URI: https://hdl.handle.net/10356/137224
DOI: 10.32657/10356/137224
Schools: School of Materials Science & Engineering 
Rights: This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MSE Theses

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