The adsorption of polymers on surfaces is an essential problem in polymer physics, as well as of key interest in technological applications. The interaction of flexible macromolecules with homogeneous substrates as a function of several system parameters (such as interaction strength between polymers and the substrate, polymer length, etc) has been widely studied in the literature. However, natural surfaces have a rather complex structure. For instance, substrates could have hydrophobic and hydrophilic zones irregular in shape as it is the case of the surface of human hair fibers of interest in cosmetic applications. Herein, we lay our focus on the fundamental case of the adsorption of hydrophilic homopolymers on heterogeneous substrates employing coarse-grained molecular dynamics simulations. Polymer chains are represented as N beads connected via springs. The substrate is comprised of beads (the same size as for polymers) of two types: hydrophobic and hydrophilic. We investigate polymer adsorption as a function of polymer chain length and polymer concentration spanning both dilute and semidilute regimes. Under dilute conditions, polymers maximize their interaction with the substrate, thus their dimension parallel to the surface exceeds the perpendicular one. Additionally, the formation of bridges across the hydrophobic zones is observed. Upon increasing polymer concentration in the system polymer coils start to overlap among each other reducing polymer size while the anisotropy in polymer size concerning the surface vanishes. The understanding of polymer behavior in systems containing surfaces is of great importance to optimize their use of film formers as desired in general for industrial applications. In cosmetic applications, in particular, sustainability and ecological impact are aspects of great importance that can be addressed by the right choice of the polymers employed. Thus, the investigation of homopolymer adsorption is a first step towards developing models of more complex eco-friendly macromolecules interacting with surfaces.

Polymer adsorption on bio-inspired disordered substrates

ACS Spring Meeting 2021

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