Rotational and conformational dynamics of a model polymer melt at solid interfaces

Macromolecules, ISSN: 0024-9297, Vol: 42, Issue: 24, Page: 9498-9505
2009
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  • Citations
    20
    • Citation Indexes
      20
  • Captures
    27

Article Description

Performing molecular dynamics simulations for an all-atom model, we investigate the rotational and conformational dynamics of short polyethylene oxide) chains sandwiched between two parallel TiO surfaces. In this nanocomposite, the polymer forms layers parallel to the solid interfaces. At the studied temperatures, a substantial slowdown of polymer dynamics with respect to the bulk behavior is essentially restricted to the layer next to the solid interface. While the rotational correlation times in the surface layer follow an Arrhenius law, non-Arrhenius behavior is found for segments in the center of the slit. Moreover, unlike bulk segments, interfacial segments show a jump diffusion mechanism. In the immediate vicinity of the solid surfaces, the waiting times between conformational transitions are longer and the probabilities for back jumps are higher, in harmony with the slower loss of orientational correlation in these regions. The transitions between the conformational states do not obey Poisson statistics, particularly in the layer next to the interface. At sufficiently low temperatures, correlated forward-backward motion is an important aspect of the conformational relaxation, leading to strongly nonexponential distributions for the waiting times of the dihedrals in the various conformational states. ©2009 American Chemical Society.

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