随着人类经济的快速发展和工业化进程的加快，人们面临能源短缺和环境恶化的两大困境。而海水淡化、废水回收和电池被认为是解决淡水资源短缺和能源 环境 问题的重要方法 之一 。膜分离技术被认为是有希望解决这些问题的重要方法之一。反渗透 、 超滤 和锂 离子 电池是目前应用呈快速上升趋势的技术，对其展开微观作用机理的研究具有重要意义 。本文采用介电弛豫谱和分子动力学 模拟 方法从理论方面对高分子膜 /电解液体系的微观结构和作用机制进行了探究。 具体研究内容如下：

一、结合介电谱和全原子分子动力学模拟方法研究了 12-草酸十二烷酸甲酯基团内壁修饰的多壁碳纳米管 (MWNT-C14H25O4)掺杂聚酰胺 (PA)反渗透膜的脱盐机理。介电谱方法的研究主要包括两个方面 :(1)通过 介电谱 数据的模型分析， 结果显示 MWNT-C14H25O4/PA膜的水体积分数、平均孔径和介电参数大于 PA膜，这说明 MWNT-C14H25O4/PA的水通量高于 PA膜。 (2)进一步分析发现，相较于 PA膜， MWNT-C14H25O4/PA膜具有较高的平均电荷密度、离子溶剂化势垒和反射系数，这说明内壁改性的多壁碳纳米管的添加可以提高 PA膜的脱盐性能。在微观方面，利用 分子动力学模拟 方法计算得到了水和离子的自由体积分布、扩散系数等数据。结果表明，分子动力学模拟得到的微观数据较好地支持了介电谱方法数据得到的结论。 该 研究提供了一种方便且非入侵的方法从膜结构方面表征膜的特性。

二、利用粗粒化分子动力学模拟的方法研究了海藻酸盐在内壁改性碳纳米管 /聚酰胺掺杂反渗透膜和聚酰胺膜表面吸附的过程以及其 相互作用。结果表明，海藻酸盐在 300ns后接近 PA表面，而 MWNT-C14H25O4/PA膜对海藻酸盐的吸附存在延迟，在模拟过程的 500ns内未接近 MWNT-C14H25O4/PA表面。 MWNT修饰官能团中的极性氧原子增加了 PA膜的负电荷，使其排斥带负电荷的海藻酸盐，从而延缓了吸附过程。另外水分子的扩散系数在MWNT-C14H25O4/PA膜中较大、海藻酸盐与 MWNT之间的径向分布函数较小都说明了海藻酸盐不易污染 MWNT-C14H25O4/PA膜。

三、利用介电谱和粗粒化分子动力学模拟方法研究了 Na+，Cl-的存在对共聚邻苯二氮酮联苯醚砜 (PPBES)超 滤膜过滤刚果红带电染料的影响。介电谱方法分析得到 Na+和 Cl-的存在使 PPBES膜的水体积分数、膜孔参数和膜孔介电参数的增加，结合膜污染模型，推断出Na+和Cl-的加入使刚果红染料不易在的加入使刚果红染料不易在PPBES膜表面吸附，进而使膜表面吸附，进而使PPBES膜水通量的增膜水通量的增加。进一步用粗粒化分子动力学方法获得加。进一步用粗粒化分子动力学方法获得了了刚果红染料分子与刚果红染料分子与PPBES膜在不同离子浓度膜在不同离子浓度体系中的最近的距离、径向分布函数和扩散系数数据体系中的最近的距离、径向分布函数和扩散系数数据，该数据，该数据进一步支持了进一步支持了介电谱方法得介电谱方法得到的到的结论。

四、采用介电谱方法对锂离子电池隔膜采用介电谱方法对锂离子电池隔膜/LiCl溶液体系进行了溶液体系进行了研究。锂离子在隔膜中的研究。锂离子在隔膜中的迁移能力和电解液的浸润性是评价锂离子电池隔膜的重要因素。通过计算得到了膜、膜孔、迁移能力和电解液的浸润性是评价锂离子电池隔膜的重要因素。通过计算得到了膜、膜孔、溶液的介电常数和电导率以及锂离子的溶剂化能垒。计算结果显示锂离子溶剂化能垒较小，溶液的介电常数和电导率以及锂离子的溶剂化能垒。计算结果显示锂离子溶剂化能垒较小，膜孔介电常数接近于电解液介电常数，这说明该隔膜可以允许锂离子自由通过，并且被膜孔介电常数接近于电解液介电常数，这说明该隔膜可以允许锂离子自由通过，并且被LiCl溶液充分浸润。溶液充分浸润。

With the rapid development of human economy and the acceleration of the process of industrialization, energy shortage and environmental deterioration are globally challenging problem in our future. Seawater desalination, brackish water desalination, wastewater recovery and battery are considered as the important methods to solve the problems of fresh water shortage and energy. Membranes separation is considered to be a very promising technique to address this issue. Reverse osmosis, ultrafiltration technology and lithium battery are rapidly increasing technologies, and it is of great significance to study the microscopic mechanism of action. In this paper, the microstructure and mechanism of polymer membranes/electrolyte system were studied theoretically by dielectric relaxation spectroscopy and molecular dynamics simulation. The specific research contents are as follows:
(1) Desalination mechanism of multi-walled carbon nanotubes (MWNT) modified by methyl Dodecanoate group on the inner wall doped polyamide (PA) reverse osmosis membrane was studied by combining dielectric relaxation spectrum (DRS) and molecular dynamics (MD) simulation. DRS analysis mainly focus on two aspects: (1) the water volume fraction, average pore size and dielectric parameters of MWNT-C14H25O4/PA membranes obtained by model analysis of DRS data were higher than PA membrane, which indicate that the water flux of MWNT-C₁₄H₂₅O₄/PA was higher than that of PA membranes. (2) Further analysis shows that MWNT-C₁₄H₂₅O₄/PA membrane has high average charge density, ion solvation barrier and reflection coefficient, which indicates that the added interior-modified MWNT could improve the salt rejection of PA membranes. In the microscopic aspect, the desalination behavior of MWNT-C₁₄H₂₅O₄/PA and PA membrane was analyzed from the aspects of free volume distribution,dynamic diffusion process of water and ions. The results show that the microscopic data of MD well support the conclusion of DRS method. This study provides a convenient and non-invasive methodology to characterize the properties of the membrane from aspect of membrane structure.
(2) Adsorption of alginate on MWNT-C₁₄H₂₅O₄/PA and PA membranes surfaces and surface?alginate interactions in an aqueous environment was investigated using coarse-grained molecular dynamics. Results showed that alginate observed in close proximity to PA surface after 300 ns, while the MWNT-C₁₄H₂₅O₄/PA showed delayed adsorption of alginate with alginate not observed near to MWNT-C₁₄H₂₅O₄/PA surface within 500 ns. The polar oxygen group in the function groups of modification MWNT increased the negative charge of PA membrane, which repelled negatively charged alginate, thereby delaying the adsorption process. In addition, the larger diffusion coefficient of water molecules in MWNT-C₁₄H₂₅O₄/PA membrane and the smaller radial distribution function between alginate and MWNT indicate that alginate was not easy to adsorption in MWNT-C₁₄H₂₅O₄/PA membrane surface.
(3) Adsorption of charged Congo red dye on phthalazinone biphenyl ether sulfone (PPBES) ultrafiltration membrane surfaces were investigated in the presence and absence of ions using DRS and coarse-grained MD methods. DRS analysis showed that the presence of Na⁺ and Cl^- makes the water volume fraction, pore parameters and pore dielectric parameters of PPBES membrane increase. Combined with the membrane pollution model, we conclude that the addition of Na⁺ and Cl^- makes Congo red dye not easy to adsorb on the surface of PPBES membrane and increases the water flux. The data of distance, radial distribution function and diffusion coefficient between Congo red dye and PPBES membrane obtained by coarse-grained MD method further support the DRS conclusion.
(4) The battery membrane/LiCl solution system of Li-ion battery were studied by DRS. The transport of lithium ion in battery separator and the wettability by electrolyte are important factors to evaluate the separator. Results showed that the solvation energy barrier of lithium ion is small and the dielectric constant of membrane pore is close to that of electrolyte, which indicate that the battery membrane could allow lithium ions transport freely and adequately wetted by LiCl solution