Coarse-grained molecular models of the surface of hair

Weiand, Erik; Ewen, James P.; Koenig, Peter H.; Roiter, Yuri; Page, Steven H.; Angioletti‐Uberti, Stefano; Dini, Daniele

doi:10.1039/d1sm01720a

“…The formation of droplets between hydrophobic monolayers has also been observed in previous NEMD simulations. 106 At higher damage levels, water progressively attaches to regions where the lipids have been removed, which is consistent with previous MD simulations 33 and AFM experiments, 107 For the ultimately bleached hair surfaces (χ N = 1.0), an equivalent atomistic water number density per unit area of N W A −1 = 96 nm -2 is obtained, which is distributed within six hydration layers normal to the two surfaces. This value is in good agreement with the largest value used in all-atom NEMD simulations that studied the friction of water confined between hydrophilic alkylsilane self-assembled monolayers (N W A −1 = 85 nm -2 ).…”

Section: Nemd Simulations Of Wet Contactssupporting

confidence: 85%

“…These surfaces were similar to those proposed recently in our CG-MD wetting study on hair. 33 The CCP AFM friction experiments were performed using a Bruker (Billerica, Mas- Using the Johnson-Kendall-Roberts (JKR) 86 contact theory modified by Reedy 87 for thin coatings with experimentally measured adhesion and elastic properties of the silica (substrate) 88 and surfactant monolayers (coating), 89 we estimate that the contact pressure in these experiments is 5-79 MPa. Further details on this calculation and additional estimation methods are given in the Supplementary Material (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…10,[12][13][14]22,24 During bleaching, the 18-MEA layer is partially removed by oxidation of the cysteine, which leads to the formation of negatively charged cysteic acid groups, making the hair surface more hydrophilic. 19,[31][32][33] From experiments in humid air environments (relative humidity, RH ≈ 50%), capillary condensation has been proposed as a possible mechanism for the increase in adhesion and friction from bleaching hair. 12 Indeed, capillary condensation is known to increase friction on hydrophilic surfaces more than hydrophobic ones.…”

Section: Introductionmentioning

confidence: 99%

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Nanoscale Friction of Biomimetic Hair Surfaces

Weiand

¹

,

Ewen

²

,

Roiter

³

et al. 2022

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We investigate the nanoscale friction between biomimetic hair surfaces using chemical colloidal probe atomic force microscopy experiments and nonequilibrium molecular dynamics simulations. In the experiments, friction is measured between water-lubricated silica surfaces functionalised with monolayers of either octadecyl or sulfonate groups, which are representative of the surfaces of virgin and ultimately bleached hair, respectively. In the simulations, friction is monitored between coarse-grained model hair surfaces with different levels of chemical damage, where different fractions of grafted lipid molecules are randomly replaced with sulfonate groups. The sliding velocity dependence of friction can be described using an extended stress-augmented thermally activation model. As the damage level increases, the friction generally increases, but its sliding velocity-dependence decreases. At low sliding speeds, which are closer to those encountered physiologically and experimentally, we observe a monotonic increase of friction with the damage ratio, which is consistent with our new experiments using biomimetic surfaces and previous ones using real hair. This observation demonstrates that modified surface chemistry, rather than roughness changes or subsurface damage, control the increase in nanoscale friction of damaged hair. We expect the experimental and computational model surfaces proposed here to be useful to screen the tribological performance of hair care formulations.

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“…Weiand et al modelled partially damaged hair by random removal of 18-MEA molecules from a healthy hair substrate. 26 Morozova et al mapped experimental AFM images to create an interacting surface with hydrophilic and hydrophobic zones. 28 Based on the experimental descriptions of bleached hair (Figure 2), we chose to model the partially damaged surface more in line with the patches modelled by Morozova et al However, in contrast to Morozova et al, our partially damaged surface is a simplification of the highly non-uniform topology characteristic of the damaged patches to support system sizes accessible at the length scale of the current simulations.…”

Section: Simulations Of Formulations In Contact With a Model Hair Sur...mentioning

confidence: 99%

Shearing Friction Behaviour of Synthetic Polymers Compared to a Functionalized Polysaccharide on Biomimetic Surfaces: Models for the Prediction of Performance of Eco-designed Formulations

Coscia

¹

,

Shelley

²

,

Browning

³

et al. 2022

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0

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The substitution of natural, bio-based and/or biodegradable polymers for those of petrochemical origin in consumer formulations has become an active area of research and development as the sourcing and destiny of material components becomes a more critical factor in product design. These polymers often differ from their petroleum-based counterparts in topology, raw material composition and solution behaviour. Effective and efficient reformulation that maintains comparable performance to existing products requires a deep understanding of the differences in behaviour between polymers. In this work, we simulate the tribological behaviour of three topologically distinct polymers in simplex solutions in presence of surfactants and in contact with hair-biomimetic patterned surfaces: a strongly charged polyelectrolyte poly-(diallyldimethylammonium chloride) (Merquat 100TM, Polyquaternium 6), a zwitterionic copolymer of acrylic acid, 3-trimethylammonium propyl methacrylamide chloride and acrylamide, (Merquat 2003TM, Polyquaternium 53) and one generic functionalized polysaccharide. Merquat 100TM is a relatively simple linear cationic homopolymer. Merquat 2003TM is a pseudorandom block copolymer with a hydrophilic linear block and a brush-like cationic block. The chosen polysaccharide is a highly branched, amphiphilic and quanternized polymer with a cellulose-like backbone. Such topological differences are expected to affect rheological properties, as well as their direct interaction with structured biological substrates. Using a refined Martini-style coarse-grained model we describe the polymer-dependent differences in aggregation behaviour as well as selective interactions with the surface depending on the structure. Finally, we introduce a formalism to characterize the response of the solution to shear as an initial study on lubrication properties, that define the sensorial performace of these systems in cosmetics (i.e. , manageability, touch, etc.). The tools and techniques presented in this work illustrate the strength of molecular simulation in eco-design of formulation as a complement to experiment. These efforts help advance our understanding of how we can relate complex atomic-scale solution behaviour to relevant macroscopic properties. We expect these techniques to play an increasingly important role in advancing strategies for green polymer formulation design by providing an understanding for how new polymers could reach and even exceed the level of performance of existing polymers.

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“…The reduction in the number of degrees of freedom in the system also developed experimentally consistent CG models which enabled them to reproduce the wetting properties of healthy and damaged hair surfaces. 26 One can further increase computational efficiency in CG systems by replacing all solvent molecules with an implicit solvent.…”

Section: Introductionmentioning

confidence: 99%

Shearing Friction Behaviour of Synthetic Polymers Compared to a Functionalized Polysaccharide on Biomimetic Surfaces: Models for the Prediction of Performance of Eco-designed Formulations

Coscia

¹

,

Shelley

²

,

Browning

³

et al. 2022

Preprint

0

View full text Add to dashboard Cite

The substitution of natural, bio-based and/or biodegradable polymers for those of petrochemical origin in consumer formulations has become an active area of research and development as the sourcing and destiny of material components becomes a more critical factor in product design. These polymers often differ from their petroleum-based counterparts in topology, raw material composition and solution behaviour. Effective and efficient reformulation that maintains comparable performance to existing products requires a deep understanding of the differences in behaviour between polymers. In this work, we simulate the tribological behaviour of three topologically distinct polymers in simplex solutions in presence of surfactants and in contact with hair-biomimetic patterned surfaces: a strongly charged polyelectrolyte poly-(diallyldimethylammonium chloride) (Merquat 100TM, Polyquaternium 6), a zwitterionic copolymer of acrylic acid, 3-trimethylammonium propyl methacrylamide chloride and acrylamide, (Merquat 2003TM, Polyquaternium 53) and one generic functionalized polysaccharide. Merquat 100TM is a relatively simple linear cationic homopolymer. Merquat 2003TM is a pseudorandom block copolymer with a hydrophilic linear block and a brush-like cationic block. The chosen polysaccharide is a highly branched, amphiphilic and quanternized polymer with a cellulose-like backbone. Such topological differences are expected to affect rheological properties, as well as their direct interaction with structured biological substrates. Using a refined Martini-style coarse-grained model we describe the polymer-dependent differences in aggregation behaviour as well as selective interactions with the surface depending on the structure. Finally, we introduce a formalism to characterize the response of the solution to shear as an initial study on lubrication properties, that define the sensorial performace of these systems in cosmetics (i.e. , manageability, touch, etc.). The tools and techniques presented in this work illustrate the strength of molecular simulation in eco-design of formulation as a complement to experiment. These efforts help advance our understanding of how we can relate complex atomic-scale solution behaviour to relevant macroscopic properties. We expect these techniques to play an increasingly important role in advancing strategies for green polymer formulation design by providing an understanding for how new polymers could reach and even exceed the level of performance of existing polymers.

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Coarse-grained molecular models of the surface of hair

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...

Cited by 15 publications

References 103 publications

Nanoscale Friction of Biomimetic Hair Surfaces

Nanoscale Friction of Biomimetic Hair Surfaces

Shearing Friction Behaviour of Synthetic Polymers Compared to a Functionalized Polysaccharide on Biomimetic Surfaces: Models for the Prediction of Performance of Eco-designed Formulations

Shearing Friction Behaviour of Synthetic Polymers Compared to a Functionalized Polysaccharide on Biomimetic Surfaces: Models for the Prediction of Performance of Eco-designed Formulations

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