| 초록 |
Monte Carlo simulations of polyethylene (PE) nanofiber, which contains up to 72 chains of C100H204 and have the radius ~ 5.0 nm, have been produced and equilibrated on the second nearest neighbor diamond (2nnd) lattice. In these fibers, the density profiles are hyperbolic, with end beads being more abundant than the middle beads at the surface. There are orientational preferences at the surface on the scale of individual bond and whole chains. Surface energies can be calculated directly from the on-lattice energies. Comparison of fiber with different thickness (the range from 5.6 to 7.6 nm), which contain different number of chains, does not indicate any significant differences in local and global equilibrium properties. Simulation of the crystallization quenched from the melt to 298 K shows that the nanofiber adopts a configuration dominated by extended chains aligned parallel to the fiber axis. The vicinity of the fiber axis is less dense, and less well ordered, than the portions of the fiber located further from the fiber axis. Annealing at ~ 10 K below its melting temperature finds that this low-density region inside the fiber is not easily removed.
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