ON THE INTERPRETATION OF RIPPLE POLYMER INTERDIFFUSION EXPERIMENTS IN TERMS OF MODELS FOR BULK SINGLE-CHAIN DYNAMICS

The short-time ripple in the deuterium fraction profile observed during interdiffusion of deuterium-labeled polystyrenes, reported by Russell et al [Nature (London) 365, 235 (1993)] and Agrawal et al. [Macromolecules 27, 4407 (1994)] has been called "direct evidence of reptation." We suggest that this may overstate the present case. Models of polymer motion which lack the essential features of reptation, in particular the Rouse and polymer mode-coupling models, are shown here to also predict the qualitative results of these "ripple" interdiffusion experiments. We suggest that for ripple interdiffusion experiments to be able to place stringent restrictions on models for bulk polymer dynamics they must be done with higher resolution of the ripple, and be combined with a more detailed understanding of the equilibrium structure of polymer fluids near interfaces. © 1995 American Institute of Physics. © 1995 American Institute of Physics.