Chain conformation in thin polymer layers as revealed by simulations of ideal random walks.

A confinement-induced mode was discovered in thin cis-1,4-polyisoprene (PI) layers if the film thickness becomes comparable with the size of the PI coil (A. Serghei, F. Kremer, to be published in Phys. Rev. Lett.). It was assigned to the fluctuation of the terminal subchains which are formed by the immobilization of chain segments at the contact with a confining interface. In the present paper we discuss the results of simulations done in order to gain an additional insight into the nature of this novel relaxation process. It turns out that the simulations of the chains as pinned random walks reproduce most of the essential features observed in the experiment.