Rapid viscoelastic spreading

We investigate the rapid spreading dynamics of a viscoelastic drop on a solid. Upon contact, surface tension drives a fast motion of the contact line along the substrate. Here we resolve this motion for viscoelastic liquids by experiments on aqueous polymer solutions of varying concentration. It is found that while the contact line motion is only mildly affected by the polymers, the interface profile becomes much sharper owing to singular polymer stress. This behavior is reminiscent of that observed for viscoelastic drop coalescence; in this context we revisit the analogy between spreading and coalescence, which sheds light also on the spreading of Newtonian liquids