圆筒受限高分子链的Monte Carlo模拟  

Monte Carlo simulation of polymer chain confined in cylinder

作　　者：李安邦[1] 缪晗[1] 

机构地区：[1]华中师范大学物理学院,湖北武汉430079

出　　处：《计算机与应用化学》2010年第5期654-658,共5页Computers and Applied Chemistry

摘　　要：高分子链的构象性质是高分子研究中的重要研究对象。当高分子链受限于各种微腔中时,链的构象熵与微腔的形状和体积有十分密切的关系。平面壁限制条件下的高分子构象研究极多,然而在考虑高分子链穿越半径很小的纳米管时,有必要将微腔视为细长管道,而不是平面壁,因此约束在软管中的高分子链在近几年中得到了更多的重视。现有文献中主要讨论构象和能量与约束半径R之间的关系,没有考虑温度T的影响。本文采用自避行走(SAW)为模型链,利用硬球链模型模拟高分子链在无限长圆筒受限条件下的结构。模型由弹性链连接的硬球构成,球与球之间通过弹性势能函数相互作用,利用标准的Metropolis算法,通过MonteCarlo模拟,改变约束半径R和与绝对温度T成反比例关系的相关系数K,分别计算了高分子链的平均回转半径,平均末端距,平均弹性势能,能量均方涨落,能量相对涨落与R、T的关系。结果表明,圆筒受限高分子链的构像主要取决于R,在R小于某个临界值时高分子链受到明显的约束作用,当R超过临界值时高分子链变为无扰链。温度T并不明显地影响受限高分子链的构象。能量性质在R较小时主要取决于R,但R为临界受限值附近时,能量性质受T影响明显,容易出现能量和涨落的状态突变。Conformational properties of polymers are important study objects. When a polymer chain is confmed in a micro-cavity, conformational entropy of the polymer is strongly related to the shape and volume of the micro-cavity. There have been lots of studies on polymers near confined to a wall, however it is necessary to regard micro-cavity as microtube rather than a wall, when we are considering polymers walking across nanotube whose radius is very small radius. In this paper, by means of the self-avoiding walk （SAW） as the model of a polymer chain, the properties of conformation and energy of a polymer chain confined in an infinite cylinder were studied. The model was consisted of globules connected by elastic bonds. Monte Carlo simulation based on Metropolis arithmetic was performed with vaVies cylinder＇s radii R and interrelated coefficients K which were reverse proportional to absolute temperature T. The mean gyration radius, mean end-end distance, mean elastic energy, root mean square fluctuation of energy and mean relative fluctuation of energy of the confined polymer chain were calculated. Results showed that the chain＇s conformational properties were mainly determined by R, the chain was distinctly confined while R was relative small, and ttmaed to be unperturbed when R was great than a criteria value. The chain＇s energy properties were also largely determined by R while R were relative small, but influenced greatly by Twhen R were near the criteria value, and abrupt changes of energy were observed in this region.

关 键 词：MONTE Carlo 受限高分子链 自避无规行走 

分 类 号：O631[理学—高分子化学]