Abstract.
We present results from molecular dynamics simulations of strictly two-dimensional (2D) polymer melts and thin polymer films in a slit geometry of thickness of the order of the radius of gyration. We find that the dynamics of the 2D melt is qualitatively different from that of the films. The 2D monomer mean-square displacement shows a t8/15 power law at intermediate times instead of the t1/2 law expected from Rouse theory for nonentangled chains. In films of finite thickness, chain entanglements may occur. The impact of confinement on the entanglement length Ne has been analyzed by a primitive path analysis. The analysis reveals that Ne increases strongly with decreasing film thickness.
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We feel that our results should not be interpreted in the sense that the criterion for an increase of Ne is necessarily h < Rg bulk. It may be that it rather requires h to become smaller than the tube diameter dt bulk. A test of this hypothesis necessitates simulations of larger N because the two scales, dt bulk and Rg bulk, are not well separated for the studied chain length N=256
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Meyer, H., Kreer, T., Cavallo, A. et al. On the dynamics and disentanglement in thin and two-dimensional polymer films. Eur. Phys. J. Spec. Top. 141, 167–172 (2007). https://doi.org/10.1140/epjst/e2007-00035-9
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DOI: https://doi.org/10.1140/epjst/e2007-00035-9