Monte Carlo simulation of PFPE molecular conformation in the ultrathin liquid films
Monte Carlo simulation of PFPE molecular conformation in the ultrathin liquid films
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超薄液膜中PFPE分子构象的蒙特卡罗模拟
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
Junho Choi
中科院分区：
文献类型：
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作者：
T. Kato;M. S. Mayeed;M. Kawaguchi;Junho Choi
将爬行算法应用于简化的全氟聚醚 (PFPE) 珠弹簧晶格聚合物模型，进行 NVT Monte Calro 模拟来模拟本体和超薄膜聚合物构象。在本体中使用珠-珠 Lennard-Jones (LJ) 电势，并且在超薄膜条件下添加该基板-珠 LJ 电势。 Fomblin Z (Ausimont) 的分子量为 3840 和 1700 g/mol，是在室温和压力条件的假设下考虑的。对于块体和超薄膜条件，均考虑约 80-82% 的最大体积分数，这是室温条件下熔体的典型情况。 R g 在 x、y 和 z 方向上的平均分量 R gx 、R gy 和 R gz 在整体上几乎彼此相等，表示聚合物的平均形状为球体。在几纳米厚的超薄膜中，引入了底部基底表面和不同纳米薄膜高度的顶部限制，以保持最大体积分数与本体相似。与它们的体积值相比，R g 和 R gz 减小，R gx 和 R gy 增大（这里，xy 平面平行于基底表面，z 表示距同一表面的高度），并且在取决于分子量的特定超薄膜厚度下开始膜厚度减小。结果还揭示了构象变化对密度变化的影响。
Applying the reptation algorithm to a simplified perfluoropolyether (PFPE) bead-spring off lattice polymer model, an NVT Monte Calro simulation has been performed to simulate the bulk and ultrathin film polymer conformation. Bead-bead Lennard-Jones (LJ) potential is used in the bulk and with this substrate-bead LJ potential is added in the ultrathin film condition. Molecular weights of 3840 and 1700 g/mol for Fomblin Z (Ausimont) are considered with the assumption of room temperature and pressure condition. Maximum volume fraction of approximately 80-82%, typical of a melt at room condition, is considered for both the bulk and the ultrathin film condition. The average components of R g in the x, y and z directions R gx , R gy and R gz are almost equal to each other in the bulk denoting the average shape of a polymer as a sphere. In the ultrathin films of several nano-meters thick a substrate surface at the bottom and a top restriction at film heights of different nano-meters are introduced keeping the maximum volume fraction similar to that of the bulk. R g and R gz decrease and R gx and R gy increase (here, the xy plane is taken parallel to the substrate surface and z denotes the height from the same surface) in comparison to their bulk values with the decrease of film thickness initiated at a specific ultrathin film thickness which depends on the molecular weight. Effect on density variation due to conformation change is also revealed in the results.