Motions and Relaxations of Confined Liquids

Abstract

When a liquid is confined in a narrow gap (as near a cell membrane, in a lubricated contact between solids, or in a porous medium), new dynamic behavior emerges. The effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates. These effects are more prominent, the thinner the liquid film. They appear to be the manifestation of collective motions. The flow of liquids under extreme confinement cannot be understood simply by intuitive extrapolation of bulk properties. Practical consequences are possible in areas from tribology and materials processing to membrane physics.

Nonlinear Rheology of Confined Polymer Melts under Oscillatory Flow

“…14 We assume here that the last condition is satisfied. However, if this frequency exceeds the inverse Rouse relaxation time of the bridge, T 0 -1 ) τ 0 -1 (a/h) 4 , the bridges do not have time to come to equilibrium and thus are equivalent to other (nonbridging) chain fragments. We restrict the consideration in this section to the region, where the effect of bridges is crucial, ω < τ 0 -1 (a/h) 4 .…”

“…The relaxation time of the loop is the Rouse time T 0 ) τ 0 (h/a) 4 , so the storage modulus is Taking into account that in regime 2.c G′ > G 1 ′, we can write the final equations for the moduli as B. Nonlinear Regimes. 1.…”

“…A number of papers are devoted to this problem, in particular to the nanorheology of confined polymer melts. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Confined polymer liquids show some features that are different from those of polymer liquids in the bulk. They show extremely large relaxation time even in the regime of rather short polymer chains which cannot create entanglements.…”

Nanocrystal Diffusion in a Liquid Thin Film Observed by in Situ Transmission Electron Microscopy

“…These include solvent surface fluctuations 2 , airliquid\substrate-liquid interface structure 4,5 as well as the intrinsic differences in the relaxation and transport properties in an ultra thin liquid film compared to its bulk [6][7][8][9] .…”

Solid or Liquid? Solidification of a Nanoconfined Liquid under Nonequilibrium Conditions

“…1 In liquid films close to a flat solid surface, molecular layering is observed, [2][3][4] which is enhanced by confinement between two solid surfaces. New tools to study confined liquids include surface force apparatus (SFA), 2,5,6 atomic force microscopy (AFM), 7,8 and spectroscopic techniques 9 such as fluorescence correlation spectroscopy (FCS). 10 Various experiments have yielded mutually exclusive findings on the dynamics of these confined systems.…”