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 behaviour is reminiscent of that observed for viscoelastic drop coalescence; in this light we revisit the analogy between spreading and coalescence, which sheds new light also on the spreading of Newtonian liquids.