Confinement and complex viscosity

Abstract

Whereas much is known about the complex viscosity of polymeric liquids, far less is understood about the behavior of this material function when macromolecules are confined. By confined, we mean that the gap along the velocity gradient is small enough to reorient the polymers. We examine classical analytical solutions [O. O. Park and G. G. Fuller, “Dynamics of rigid and flexible polymer chains in confined geometries. II. Time-dependent shear flow,” J. Non-Newtonian Fluid Mech. 18, 111–122 (1985)] for a confined rigid dumbbell suspension in small-amplitude oscillatory shear flow. We test these analytical solutions against the measured effects of confinement on both parts of the complex viscosity of a carbopol suspension and three polystyrene solutions. From these comparisons, we find that both parts of the complex viscosity decrease with confinement and that macromolecular orientation explains this. We find the persistence length of macromolecular confinement, Lp, to be independent of both λω and λγ̇0.

Exploring the Depth-Dependent Microviscosity inside a Micelle Using Butterfly-Motion-Based Fluorescent Probes

“…To gain microscopic insights into the structure and dynamics of micelles, fully atomistic MD simulations of DPAC-F3@C 16 TAB , DPAC-F7@C 16 TAB , and DPAC-F15@C 16 TAB were conducted. The initial micellar structure was established by arranging 100 C 16 TAB molecules and 1 probe molecule through Packmol. − The concentration of the simulated micellar aqueous solution was set at 10 –3 M by adding water molecules and bromide ions to the system to maintain electrical neutrality, which is consistent with our experimental conditions. The selection of the number of ionic liquid molecules was based on studies from previous literature…”