Short Time Dynamics of Polymer Diffusion

Abstract

We investigated diffusion between deuterated and protonated polystyrene films at short times using neutron reflectometry (NR) and nuclear reaction analysis (NRA). We covered six orders of magnitude in time and identified two time regimes of diffusion with a crossover at the reptation time τ _rep. Below τ _rep the interfacial profile can be described by two superposed error functions attributed to the Rouse-type mobility and reptation. The contribution due to reptation shows a discontinuity at the position of the interface. There are some strong indications for an enhanced concentration of chain ends at the interface. The reliability of the results is supported by the agreement of the three values of τ _rep obtained by the use of the two complementary techniques.