| 초록 |
Polymer melt confined in a nanoscale space shows dynamic properties distinct from the bulk state, and understanding the behavior of the confined system is important for various application such as nanocomposites, lubricants, and thin films for electric devices. Polymer dynamics are generally discussed in terms of two models: (1) Rouse dynamics for short unentangled chains, and (2) reptation dynamics for highly entangled chains. In the Rouse model, the fluid surrounding a chain relaxes rapidly, providing a stochastic background for a chain’s motion. In the reptation model, on the other hand, the surrounding fluid relaxes on an infinite time scale, thus presenting fixed obstacles to a chain’s motion. In the present work, we investigated the effect of confinement on the dynamics of polymer melts by using a molecular dynamics simulation. A bead-spring model and stochastic walls are used to model a polymer melt in a confined geometry. Varying the distance between two walls, various dynamic properties such as the self diffusion constant, Dself, were measured and the results were compared to that in the bulk system. From these simulation results, the effect of confinement on the crossover from the Rouse dynamics to the dynamics of the reptation model was discussed.
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