  We studied experimentally the breakup of liquid bridges made of aqueous
solutions of Poly(acrylic acid) between two separating solid surfaces with
freely moving contact lines. For polymer concentrations higher than a certain
threshold ($\sim$ 30 ppm), the contact line on the surface with the highest
receding contact angle fully retracts before the liquid bridge capillary
breakup takes place at its neck. This means that all the liquid remains
attached to the opposing surface when the surfaces are separated. This behavior
occurs regardless of the range of liquid volume and stretching speed studied.
Such behavior is very different from that observed for Newtonian liquids or
non-Newtonian systems where contact lines are intentionally pinned. It is shown
that this behavior stems from the competition between thinning of bridge neck
(delayed by extensional thickening) and receding of contact line (enhanced by
shear thinning) on the surface with lower receding contact angle. If the two
surfaces exhibit the same wetting properties, the upper contact line fully
retracts before the capillary breakup due to the asymmetry caused by gravity,
and, therefore, all the liquid remains on the lower surface.
