Shear rate threshold for the boundary slip in dense polymer films

Abstract

The shear rate dependence of the slip length in thin polymer films confined between atomically flat surfaces is investigated by molecular dynamics simulations. The polymer melt is described by the bead-spring model of linear flexible chains. We found that at low shear rates the velocity profiles acquire a pronounced curvature near the wall and the absolute value of the negative slip length is approximately equal to thickness of the viscous interfacial layer. At higher shear rates, the velocity profiles become linear and the slip length increases rapidly as a function of shear rate. The gradual transition from no-slip to steady-state slip flow is associated with faster relaxation of the polymer chains near the wall evaluated from decay of the time autocorrelation function of the first normal mode. We also show that at high melt densities the friction coefficient at the interface between the polymer melt and the solid wall follows power law decay as a function of the slip velocity. At large slip velocities the friction coefficient is determined by the product of the surface induced peak in the structure factor, temperature and the contact density of the first fluid layer near the solid wall.

37 pages, 16 figures

References in corpus (10)

• Boundary conditions at a fluid - solid interface
• Slip behavior in liquid films on surfaces of patterned wettability: Comparison between continuum and molecular dynamics simulations
• Influence of wetting properties on the hydrodynamic boundary condition at a fluid-solid interface
• Nanorheology : an Investigation of the Boundary Condition at Hydrophobic and Hydrophilic Interfaces
• Surface Roughness and Hydrodynamic Boundary Conditions
• Rate-dependent slip boundary conditions for simple fluids
• Effect of surface roughness on rate-dependent slip in simple fluids
• Temperature dependence of the slip length in polymer melts at attractive surfaces
• Slip boundary conditions for shear flow of polymer melts past atomically flat surfaces
• Rheological study of polymer flow past rough surfaces with slip boundary conditions

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• Analysis of Boundary Slip in a Flow with an Oscillating Wall
• Interfacial friction between semiflexible polymers and crystalline surfaces
• Microscopic determination of macroscopic boundary conditions in Newtonian liquids
• Droplet transport in a nanochannel coated by hydrophobic semiflexible polymer brushes: the effect of chain stiffness
• Multiscale Approach to Fluid-Solid Interfaces: An overview of methodologies coupling fluid mechanics to molecular dynamics and quantum theory