有机蒙脱石层间微结构的分子模拟

MOLECULAR DYNAMIC SIMULATION ON INTERLAYER MICRO-STRUCTURE IN ORGANIC MONTMORILIONITE

采用分子动力学模拟方法，对含烷基长链阳离子表面活性剂改性有机蒙脱石的层间域内分子环境及烷基长链排列状况进行模拟研究，并考察改性剂负载量与层间域含水量的改变对烷基链排列方式和活动性以及表面活性剂离子中N，C原子的分布状况的影响。1．0倍阳离子交换容量改性的有机蒙脱石在含少量水的情况下（干态），N，C原子均呈双层分布，表明烷基长链为双层平卧排列。含水量的提高（湿态）会导致烷基链从双层分布向在层间域内均匀分布转变。2．0倍阳离子交换容量改性的有机蒙脱石在含少量水的情况下（干态），烷基链呈双层倾斜分布于层间域内，烷基链的头部靠近四面体片层。含水量的提高（湿态）对烷基链在层间域内分布状态影响有限，但会导致烷基链整体向层间域中心平面移动，水分子优先占据靠近四面体片层的位置。

Molecular dynamics simulation technique was used to investigate the molecular environment and the alkyl chains arrangement in the interlayer of cation surfactant modified montmorillonite, and the influence caused by water content in organic montmorillonite with different surfactant loading was studied. For lower surfactant loading samples, the atomic density profiles revealed that C and N atoms were arranged in two layers which agreed to the lateral bilayer of alkyl chains bilayer. The N and C atomics were spread averagely in the interlayer space when the water content rose. For higher surfactant loading samples, when the water content was low, the Cm and N atoms were close to the clay surface and arranged in two layers, and the water molecules were located at the middle of interlayer. The Cm, C and N atoms kept the arrangement in two layers when the water content rose, but their positions were moved toward the middle of interlayer. The simulation revealed that the water molecules were anchored above the surface six-member rings through H-bonds between water hydrogen and surface oxygen when the water content was high. When water content increased, the rest water positioned nearby the top and bottom surface of interlayer space rather than distributed in the interlayer space.