Adsorption-induced slip inhibition for polymer melts on ideal substrates

Abstract

Hydrodynamic slip, the motion of a liquid along a solid surface, represents a fundamental phenomenon in fluid dynamics that governs liquid transport at small scales. For polymeric liquids, de Gennes predicted that the Navier boundary condition together with polymer reptation implies extraordinarily large interfacial slip for entangled polymer melts on ideal surfaces; this Navier-de Gennes model was confirmed using dewetting experiments on ultra-smooth, low-energy substrates. Here, we use capillary leveling—surface tension driven flow of films with initially non-uniform thickness—of polymeric films on these same substrates. Measurement of the slip length from a robust one parameter fit to a lubrication model is achieved. We show that at the low shear rates involved in leveling experiments as compared to dewetting ones, the employed substrates can no longer be considered ideal. The data is instead consistent with a model that includes physical adsorption of polymer chains at the solid/liquid interface.

Influence of outer-layer finite-size effects on the dewetting dynamics of a thin polymer film embedded in an immiscible matrix

“…Indeed, the PS thickness at which the rate begins to strongly increase in Figure 2a) is roughly 50 nm. This value: is only slightly above the thickness at which apparent glass transition temperature reductions begin to be observed; 4,6,62 is a typical value of slip lengths for PS melts on certain hydrophobic coatings; [63][64][65] and approaches the length scales for which disjoining forces may be operative. [66][67][68] However, invoking either slip or disjoining forces does not allow to quantitatively rationalize the data.…”

Viscoelasticity-Induced Onset of Slip at the Wall for Polymer Fluids

“…The no slip boundary condition (equal solid and fluid velocities), has long been commonly used. Numerous violations of this no slip boundary condition have however been reported in the past decades, both experimentally [12][13][14][15][16][17][18][19][20][21][22][23][24][25] and numerically [26][27][28][29][30][31].…”

“…Balancing friction and viscous stresses, one can define the extrapolated distance to the interface where the velocity profile vanishes to zero, the so-called slip length b: b = η/k. The order of magnitude of the slip length varies from few nanometers [12, 14-16, 18, 26-28, 30] for simple fluids to micrometers [13,17,[19][20][21][22][23][24][25] for complex fluids.…”

Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

“…This prediction was confirmed recently in studies of dewetting thin polymer films 18 and using velocimetry measurements. 19,20 For adsorbing surfaces or surfaces with grafted chains, the field is still active 21,22 but a mature understanding both on the experimental 14 and theoretical sides 23 has been reached to capture the main picture. The dynamics of dilute polymer solutions near interfaces has also received significant attention.…”