| 초록 |
Thin films of polymethylene melts and binary mixtures are studied by molecular dynamics simulations using a united atom model. Simulations of both pure (n-C44H90) and binary mixture (n-C44H90+n-C13H28) systems show various melts surface structures and properties. The calculated surface tensions are in good agreements with experiments. The surface segregation of methyl groups (chain ends) is one of the remarkable features of these systems. As temperature goes up, this effect decreases indicating the energetic origin. In the binary mixture melts, the shorter chain molecules are segregated out to the surfaces due to the larger portion of methyl groups. Moreover, in the mixture systems, the longer chain molecules exhibit a higher orientational order at the surfaces than the shorter ones. |
