The role of solvent quality, inhomogeneous polymer brush composition, grafting density and number of free chains on the viscosity, friction between surfaces, and their scaling laws

• Published in: Chemical physics letters Vol. 722; pp. 124 - 131
• Main Authors: Catarino Centeno, R., Balderas Altamirano, M.A., Pérez, E., Gama Goicochea, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2019
• Subjects: Couette flow; Dissipative particle dynamics; Friction coefficient; Inhomogeneous polymer brushes; Scaling; Viscosity; Viscosity; Friction coefficient; Scaling; Couette flow; Inhomogeneous polymer brushes; Dissipative particle dynamics
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2019.03.002

[Display omitted] •Mixed polymer brushes can reduce friction between surfaces more than pure ones.•A critical grafting density is found for each type of composition.•Viscosity and friction obey scaling laws that depend on solvent quality only.•An optimal mixed brush composition is predicted, for polymers used in industry. Brushes made up of mixtures of polymers are modeled using mesoscale simulations under shear and the viscosity and the friction coefficient are obtained as functions of the chains’ grafting density, brush composition, free chain concentration, and solvent quality. We find that brushes made up of mixtures of polymers can reduce to a greater extent the friction coefficient in comparison to a mono-chain brush and that both the viscosity and the friction coefficient obey scaling laws that depend only on solvent quality. These results shed light on microscopic mechanisms that affect viscosity and friction in polymeric brushes, which are findings of interest for research on nanotribology.