| |
[摘要]：Performing molecular dynamics simulations for all all-atom model, we investigate the rotational and conformational dynamics of short poly(ethylene oxide) chains sandwiched between two parallel TiO2 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 ill 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. |
|
