纳米金属有机框架材料中聚合物单体高效吸附与取向性聚合的研究

发布时间：2018-09-01 12:42

【摘要】：利用光学各项异性材料制备的光子和光电子器件具有独特的功能和性能,成为未来新型光波导器件的研究重点之一。光学各向异性主要是指双折射性和吸收率上的二向色性,即材料对不同偏振光束的折射和吸收特性不一样。聚合物光学材料由于其成本低、加工容易、性能好和双折射性可调节等优势,具有重要的研究意义和潜在应用价值。聚合物光学材料的双折射性与聚合物材料分子链的取向度有关;取向度越高,双折射率越大。在众多提高聚合物光学材料取向度的方法中,基于金属有机框架(MOF)材料可以制备具有高取向度的聚合物材料。在此方法中,利用MOF材料作为反应容器,将聚合物单体分子吸附进MOF材料的规则排列孔道中发生聚合反应,则产物聚合物分子链也将具有和MOF材料孔道一样的高取向性。本文结合密度泛函理论、蒙特卡洛方法和分子动力学,建立甲基丙烯酸甲酯(MMA)、甲基丙烯酸三氟乙酯(TFMA)等聚合物单体以及聚甲基丙烯酸甲酯(PMMA)、聚甲基丙烯酸三氟乙酯(PTFMA)等聚合物材料和MOF材料的全原子模型,模拟MMA、TFMA在MOF材料中的吸附以及模拟PMMA、PTFMA在MOF材料中的分子动力学过程。通过分析模拟结果,得出影响聚合物单体及分子链在MOF材料中吸附特性的三个主要影响因素:A)MOF材料孔壁与聚合物单体之间的静电相互作用;并发现MOF材料的极性孔道壁与极性聚合物单体分子之间的静电相互作用对聚合物单体分子在孔道内的吸附和取向有促进作用;B)聚合物单体分子之间的静电相互作用;发现极性聚合物单体分子之间的静电相互作用使其分子间隙更加紧密,从而促进了聚合物单体分子在MOF材料中的吸附,同时对其分子取向也有一定的促进作用;C)MOF材料孔洞与聚合物单体分子之间的相对大小,亦即有机配体与聚合物单体分子之间的相对大小;模拟中选择不同长度的有机配体而得到不同的孔道大小,所吸附的聚合物单体分子数量也将不同,从而影响聚合物单体分子在MOF材料孔道中聚合的转化率和聚合物分子链的取向度。这三个因素的重要影响,为聚合物单体或MOF材料的选取、对聚合物链取向度的控制提供理论预测方法。
[Abstract]:Photons and optoelectronic devices fabricated from optically heterosexual materials have unique functions and properties and have become one of the key research areas of new optical waveguide devices in the future. Optical anisotropy mainly refers to the birefringence and the dichroism of absorptivity, that is, the material's refraction and absorption characteristics of different polarized light beams are different. Because of its advantages of low cost, easy processing, good performance and adjustable birefringence, polymer optical materials have important research significance and potential application value. The birefringence of the polymer optical material is related to the orientation degree of the molecular chain of the polymer material, and the higher the orientation degree is, the greater the birefringence is. Among many methods to improve the orientation of polymer optical materials, (MOF) materials based on organometallic frames can be used to prepare polymer materials with high orientation. In this method, polymer monomers are adsorbed into the regular arranged pores of MOF materials by using MOF as the reaction vessel, and the polymer chains will have the same high orientation as that of MOF materials. This paper combines density functional theory, Monte Carlo method and molecular dynamics. A total atomic model of methyl methacrylate (MMA), poly (methyl methacrylate), poly (trifluoroethyl methacrylate), trifluoroethyl methacrylate (PMMA), trifluoroethyl methacrylate (PTFMA) and MOF was established. The adsorption of MMA,TFMA in MOF and the molecular dynamics of PMMA,PTFMA in MOF were simulated. By analyzing the simulation results, the electrostatic interaction between the pore wall of polymer monomer and polymer monomer was obtained, which mainly affected the adsorption characteristics of polymer monomer and molecular chain in MOF material. It is also found that the electrostatic interaction between polar pore wall and polar polymer monomer molecules of MOF materials can promote the adsorption and orientation of polymer monomer molecules in the pore channels. It is found that the electrostatic interaction between polar polymer monomers makes the intermolecular gap closer, thus promoting the adsorption of polymer monomer molecules in MOF materials. At the same time, it can also promote the molecular orientation of MOF materials. The relative size between pores and polymer monomers, that is, the relative size between organic ligands and polymer monomers; When organic ligands of different lengths are selected to obtain different pore sizes in the simulation, the number of polymer monomer molecules adsorbed will also be different. Thus, the conversion of polymer monomers and the orientation of polymer chains in the pore channels of MOF were affected. The important influence of these three factors provides a theoretical prediction method for the selection of polymer monomer or MOF material and the control of orientation degree of polymer chain.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631

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