A Monte Carlo Simulation on the Effects of Chain End Modification on Freely Standing Thin Films of Amorphous Polyethylene Melts
A Monte Carlo Simulation on the Effects of Chain End Modification on Freely Standing Thin Films of Amorphous Polyethylene Melts
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DOI：
10.1021/ma000957m
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发表时间：
2000-09
期刊：
影响因子：
5.5
通讯作者：
J. Jang;R. Ozisik;W. Mattice
中科院分区：
文献类型：
--
作者：
J. Jang;R. Ozisik;W. Mattice
采用蒙特卡罗（MC）方法，在高配位点阵上研究了链端修饰对厚度为2~4Rg（回转半径）的自由站立非晶态聚乙烯薄膜的影响。旋转异构态（RIS）模型被纳入到模拟作为短程相互作用，和一个Lennard-Jones（LJ）势被用来计算长程相互作用。通过改变与中间珠相比的LJ势的阱深度（e）来引入链末端的改性。eend ≤ emiddle的链端在自由表面附近表现出分离，而eend> emiddle的链端更倾向于保留在块状区域。熵和焓都是决定链端分布的主要因素。自由表面的影响可以延伸到比Rg更远的薄膜内部。然而，对于相对有吸引力的链端（eend略大于emiddle）的情况，相当大的各向同性区域长度将是一个很好的选择。
The effects of chain end modification on freely standing amorphous polyethylene thin films with a thickness 2Rg to 4Rg (radius of gyration) are studied by a Monte Carlo (MC) simulation on a high coordination lattice. The rotational isomeric state (RIS) model is incorporated into the simulation as short-range interactions, and a Lennard-Jones (LJ) potential is used to calculate the long-range interactions. The modification of the chain ends is introduced by changing the well-depth (e) of the LJ potential as compared to the middle beads. Chain ends with eend ≤ emiddle show segregation near the free surface, but chain ends with eend ≫ emiddle prefer to remain in the bulklike region. Both entropy and enthalpy are major factors in the determination of the distribution of the chain ends. The effects of the free surface can extend farther than Rg into the interior of the thin film. However, for the case of relatively attractive chain end (eend slightly larger than emiddle), a fairly large length of isotropic reg...