  The classical Cox-Voinov theory of contact line motion provides a relation
between the macroscopically observable contact angle, and the microscopic
wetting angle as a function of contact line velocity. Here we investigate how
viscoelasticity, specifically the normal stress effect, modifies wetting
dynamics. Using the thin film equation for the second-order fluid, it is found
that the normal stress effect is dominant at small scales. We show that the
effect can be incorporated in the Cox-Voinov theory through an apparent
microscopic angle, which differs from the true microscopic angle. The theory is
applied to the classical problems of drop spreading and dip-coating, which
shows how normal stress facilitates (inhibits) the motion of advancing
(receding) contact lines. For rapid advancing motion, the apparent microscopic
angle can tend to zero in which case the dynamics is described by a new regime
that was already anticipated in Boudaoud (2007).
