Adsorption and Desorption of Polymers on Bioinspired Chemically Structured Substrates

Abstract

Natural biological surfaces exhibit interesting properties due to their inhomogeneous chemical and physical structure at the micro-and nanoscale. In the case of hair or skin, this also influences how waterborne macromolecules ingredients will adsorb and form cosmetically performing deposits (i.e., shampoos, cleansers, etc.). Here, we study the adsorption of hydrophilic flexible homopolymers on heterogeneous, chemically patterned substrates that represent the surface of the hair by employing coarse-grained molecular dynamics simulations. We develop a method in which the experimental images of the substrate are used to obtain information about the surface properties. We investigate the polymer adsorption as a function of polymer chain length and polymer concentration spanning both dilute and semidilute regimes. Adsorbed structures are quantified in terms of trains, loops, and tails. We show that upon increasing polymer concentration, the length of tails and loops increases at the cost of monomers belonging to trains. Furthermore, using an effective description, we probe the stability of the resulting adsorbed structures under a linear shear flow. Our work is a first step toward developing models of complex macromolecules interacting with realistic biological surfaces, as needed for the development of more ecofriendly industrial products.

Coarse-grained molecular models of the surface of hair

“…The shape of the damage patterns is qualitatively similar to that observed in previous AFM experiments at lower resolutions. 25,30,45 Similar coverage surface coverage projections are also observed for water and n-hexadecane (Fig. S3 in the ESI †).…”

“…Random removal of lipid chains is likely from chemical treatments such as bleaching. Other authors have observed roughly circular 45 and striped 30 damage patterns on hair surfaces. However, the size of these regions is comparable to the size of the surfaces employed in our CG-MD simulations.…”

“…The area damage ratio, w S , is selected as the damage quantification parameter in the remainder of this study, since it is most representative of the degree of damage that can be measured experimentally (e.g. from AFM scans 30,45 ). The relationship between the various damage ratios, both in vacuum and in the presence of wetting fluids, is shown in Fig.…”

“…41 Coarse-grained simulations have been employed to study the adsorption of surfactants and polymers on model hair surfaces. [42][43][44] A recent study by Morozova et al 45 used coarsegrained MD simulations to investigate the adsorption of polymers onto heterogeneous surfaces obtained from the mapping of experimental AFM data of damaged hair surfaces. The authors investigated the polymer adsorption as a function of chain length and concentration.…”

“…They also probed the stability of the adsorbed structures under shear flow. 45 Here, we present new coarse-grained molecular models for the F-layer found on the outer layer of the hair cuticle in the fully-functionalised state and at several different degrees of damage. The coarse-grained MARTINI force field 46,47 is used throughout.…”