The excess electron in polymer nanocomposites
The excess electron in polymer nanocomposites
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DOI：
10.1039/c8cp04741c
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发表时间：
2018-11-21
影响因子：
3.3
通讯作者：
Quirke, Nick
中科院分区：
文献类型：
--
作者：
Saiz, Fernan;Quirke, Nick
我们已经使用从头算分子动力学和密度泛函理论（DFT）计算在B3 LYP/6- 31 G ** 水平的理论来评估的能量和本地化的过剩电子在一些代表性的界面的聚合物纳米复合材料。这些模拟界面是由液态水和聚乙烯和二氧化硅的无定形板组合而成的。无定形二氧化硅板的壁由两种表面化学组成：Q（4）或完全脱羟基化和Q（3）/Q（4）或部分羟基化，硅烷醇含量为1.62至6.86个基团/nm（2）。我们的研究结果表明，在二氧化硅/聚乙烯系统中，过量电子将位于界面处，能量在-1.75 eV（无羟基化）和-0.99 eV（硅烷醇含量最高）之间。然而，在存在自由水膜的情况下，二氧化硅表面的化学性质对过量电子的行为的影响可以忽略不计。电子优先位于水/蒸汽界面，能量为负十分之几eV。我们的结论是，在湿聚合物纳米复合材料中的水分含量具有深远的影响，电子捕获行为，因为它产生低得多的捕获能量和更高的过剩电子迁移率相比，干燥的材料。
We have used ab initio molecular dynamics and density-functional theory (DFT) calculations at the B3LYP/6-31G** level of theory to evaluate the energy and localisation of excess electrons at a number of representative interfaces of polymer nanocomposites. These modelled interfaces are made by combining liquid water and amorphous slabs of polyethylene and silica. The walls of the amorphous silica slabs are built with two surface chemistries: Q(4) or fully-dehydroxylated and Q(3)/Q(4) or partially-hydroxylated with a silanol content between 1.62 and 6.86 groups per nm(2). Our results indicate that in silica/polyethylene systems an excess electron would sit at the interface with energies between -1.75 eV with no hydroxylation and -0.99 eV with the highest silanol content. However, in the presence of a free water film, the chemistry of the silica surface has a negligible influence on the behaviour of the excess electron. The electron sits preferentially at the water/vapour interface with an energy of minus a few tenths of an eV. We conclude that the moisture content in a wet polymer nanocomposite has a profound influence on the electron trapping behaviour as it produces much lower trapping energies and a higher excess-electron mobility compared to the dry material.