SLOW SPREADING OF POLYMER MELTS

We discuss the precursor film profiles expected to be encountered during the spreading of large N polymer melts. We introduce a new control parameter: the ratio f of bulk to substrate monomer mobility. As a function of f, a variety of shapes are encountered. For f-1, the sliding profile of Brochard and de Gennes is recovered. With increasing f the macroscopic foot predicted by Brochard and de Gennes diminishes in height and eventually vanishes. For large f, the precursor is found to spread by a new mechanism: reptation instead of hydrodynamic flow. The new precursor profile is characterized by a shoulder or step with a height on the order of the radius of gyration of the polymers. © 1990, American Chemical Society. All rights reserved.