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Šindelka K, Kowalski A, Cooke M, Mendoza C, Lísal M. Interactions of cationic surfactant-fatty alcohol monolayers with natural human hair surface: Insights from dissipative particle dynamics. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
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Weiand E, Ewen JP, Koenig PH, Roiter Y, Page SH, Angioletti-Uberti S, Dini D. Coarse-grained molecular models of the surface of hair. SOFT MATTER 2022; 18:1779-1792. [PMID: 35112700 DOI: 10.1039/d1sm01720a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We present a coarse-grained molecular model of the surface of human hair, which consists of a supported lipid monolayer, in the MARTINI framework. Using coarse-grained molecular dynamics (MD) simulations, we identify a lipid grafting distance that yields a monolayer thickness consistent with both atomistic MD simulations and experimental measurements of the hair surface. Coarse-grained models for fully-functionalised, partially damaged, and fully damaged hair surfaces are created by randomly replacing neutral thioesters with anionic sulfonate groups. This mimics the progressive removal of fatty acids from the hair surface by bleaching and leads to chemically heterogeneous surfaces. Using molecular dynamics (MD) simulations, we study the island structures formed by the lipid monolayers at different degrees of damage in vacuum and in the presence of polar (water) and non-polar (n-hexadecane) solvents. We also use MD simulations to compare the wetting behaviour of water and n-hexadecane droplets on the model surfaces through contact angle measurements, which are compared to experiments using virgin and bleached hair. The model surfaces capture the experimentally-observed transition of the hair surface from hydrophobic (and oleophilic) to hydrophilic (and oleophobic) as the level of bleaching damage increases. By selecting surfaces with specific damage ratios, we obtain contact angles from the MD simulations that are in good agreement with experiments for both solvents on virgin and bleached human hairs. To negate the possible effects of microscale curvature and roughness of real hairs on wetting, we also conduct additional experiments using biomimetic surfaces that are co-functionalised with fatty acids and sulfonate groups. In both the MD simulations and experiments, the cosine of the water contact angle increases linearly with the sulfonate group surface coverage with a similar slope. We expect that the proposed systems will be useful for future molecular dynamics simulations of the adsorption and tribological behaviour of hair, as well as other chemically heterogeneous surfaces.
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Affiliation(s)
- Erik Weiand
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - James P Ewen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Peter H Koenig
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Yuri Roiter
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Steven H Page
- Corporate Functions Analytical and Data & Modeling Sciences, Mason Business Center, The Procter and Gamble Company, Cincinnati, 45224 Ohio, USA
| | - Stefano Angioletti-Uberti
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Department of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK.
- Institute of Molecular Science and Engineering, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
- Thomas Young Centre for the Theory and Simulation of Materials, Imperial College London, South Kensington Campus, SW7 2AZ London, UK
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Luengo GS, Fameau AL, Léonforte F, Greaves AJ. Surface science of cosmetic substrates, cleansing actives and formulations. Adv Colloid Interface Sci 2021; 290:102383. [PMID: 33690071 DOI: 10.1016/j.cis.2021.102383] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 02/04/2021] [Accepted: 02/06/2021] [Indexed: 12/22/2022]
Abstract
The development of shampoo and cleansing formulations in cosmetics is at a crossroads due to consumer demands for better performing, more natural products and also the strong commitment of cosmetic companies to improve the sustainability of cosmetic products. In order to go beyond traditional formulations, it is of great importance to clearly establish the science behind cleansing technologies and appreciate the specificity of cleansing biological surfaces such as hair and skin. In this review, we present recent advances in our knowledge of the physicochemical properties of the hair surface from both an experimental and a theoretical point of view. We discuss the opportunities and challenges that newer, sustainable formulations bring compared to petroleum-based ingredients. The inevitable evolution towards more bio-based, eco-friendly ingredients and sustainable formulations requires a complete rethink of many well-known physicochemical principles. The pivotal role of digital sciences and modelling in the understanding and conception of new ingredients and formulations is discussed. We describe recent numerical approaches that take into account the specificities of the hair surface in terms of structuration, different methods that study the adsorption of formulation ingredients and finally the success of new data-driven approaches. We conclude with practical examples on current formulation efforts incorporating bio-surfactants, controlling foaming and searching for new rheological properties.
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