Slippage and nanorheology of thin liquid polymer films

Abstract

Abstract.Thin liquid films on surfaces are part of our everyday life, they serve e.g. as coatings or lubricants. The stability of a thin layer is governed by interfacial forces, described by the effective interface potential, and has been subject of many studies in the last decades. In recent years, the dynamics of thin liquid films came into focus since results on the reduction of the glass transition temperature raised new questions on the behavior of especially polymeric liquids in confined geometries. The new focus was fired by theoretical models that proposed significant implication of the boundary condition at the solid/liquid interface on the dynamics of dewetting and the form of a liquid front. Our study reflects these recent developments and adds new experimental data to corroborate the theoretical models. To probe the solid/liquid boundary condition experimentally, different ways are possible, each bearing advantages and disadvantages, which will be discussed. Studying liquid flow on a variety of different substrates entails a view on the direct implications of the substrate, the experimental focus of this study is the variation of the polymer chain length: The results demonstrate that inter-chain entanglements and in particular their density close to the interface, originating from non-bulk conformations, govern liquid slip of a polymer.

Influence of Slip on the Rayleigh-Plateau Rim Instability in Dewetting Viscous Films

“…1(a), the morphological features persist [35] and are clearly determined by slippage. The results and the scaling behavior corroborate those previously found for the growth of holes in thin films [33,42].…”

“…On AF1600 (bottom row of Fig 1), the liquid films in this study reveal small slip lengths in the range of b ≈ 0.04 μm, whereas on DTS (upper row in Fig. 1) the exact same films exhibit slip lengths in the range of 1 μm, i.e., b ≫ H. The slip lengths have been determined using the rim profile analysis method [30][31][32][33] and rationalized by a combined x-ray and neutron reflectivity study [34]. Structural details, surface roughness values, and wetting properties of the coatings are given in Ref.…”

Symmetric and asymmetric instability of buried polymer interfaces

“…It is possible to define a slippage length b, given by the ratio between the viscosity and the friction coefficient k, b = η/k. The slippage for a polymer-polymer interface can be of the order of tens of microns, as discussed elsewhere [37,38]. A simple estimation for our system is of the order of 11 μm [20,28].…”

Relaxation and intermediate asymptotics of a rectangular trench in a viscous film

“…This application relies on control of the time scales of the flow created by a surface profile to produce or erase a given surface pattern. In contrast to this technologically spectacular example is the surface of freshly applied paint which relies on the dynamics of leveling to provide a lustrous surface.Much has been learned about the physics of thin films from dewetting, where an initially flat film exposes the substrate surface to reduce the free energy of the system [9][10][11][12][13][14][15][16][17][18]. Other approaches, for example studying the evolution of surface profiles originating from capillary waves [19], embedding of nanoparticles [5], or those created by an external electric field [20,21] have also been utilized to explore mobility in thin films.…”