title: Dynamic wetting of Boger fluids.
abstract: The impact of fluid elasticity on the dynamic wetting of polymer solutions is important because many polymer solutions in technological use exhibit non-Newtonian behaviors in the high shear environment of the wedge-like flow near a moving contact line. Our former study [G.K. Seevaratnam, Y. Suo, E. Ramé, L.M. Walker, Phys. Fluids 19 (2007) Art. No. 012103] showed that shear thinning induced by a semi-flexible high molecular weight polymer reduces the viscous bending near a moving contact line as compared to a Newtonian fluid having the same zero-shear viscosity. This results in a dramatic reduction of the dependence of the effective dynamic contact angle on contact line speed. In this paper, we discuss dynamic wetting of Boger fluids which exhibit elasticity-dominated rheology with minimal shear thinning. These fluids are prepared by dissolving a dilute concentration of high molecular weight polymer in a "solvent" of the oligomer of the polymer. We demonstrate that elasticity in these fluids increases curvature near the contact line but that the enhancement arises mostly from the weakly non-Newtonian behavior already present in the oligomeric solvent. We present evidence of instabilities on the liquid/vapor interface near the moving contact line.
authors.affiliation: Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wei
authors.forename: G K
authors.initials: GK
authors.lastname: Seevaratnam
authors.forename: S
authors.initials: S
authors.lastname: Garoff
authors.forename: E
authors.initials: E
authors.lastname: Ramé
authors.forename: L M
authors.initials: LM
authors.lastname: Walker