基于非共价键的宏观薄膜对溶剂选择透过性及应用的研究

发布时间：2019-02-16 18:02

【摘要】：作为非共价键中最重要的两种弱相互作用力——氢键和阳离子-π作用力,它们所具有的能量仅为共价键能量的十几分之一甚至几十分之一;因此,很多分子在通常情况下都具有足够的能量将这种弱相互作用力破坏。所以,这类弱相互作用力在往往很容易被破坏,同时也很容易重新形成。本文正是基于这两类非共价键弱相互作用力的这一特点,一方面,我们分别利用超长一维纳米结构的α-MnO2以及V_2O_5作为结构基元构建出了一种宏观薄膜,这类薄膜因为其结构基元表面暴露的氧原子(氢键受体)而很容易与外来溶剂中的氢键供体结合形成氢键,以至于氢键供体分子另一端的基团(烷基)被暴露以薄膜表面。因此,当我们利用不同的氢键供体溶剂对薄膜进行交替处理时,薄膜表面就会交替地被不同的基团所覆盖。正是基于此,当我们利用水和乙醇分别对薄膜进行淋洗处理之后发现该薄膜对非极性有机溶剂的通透性会发生极大的改变:被水处理之后非极性有机溶剂完全不能透过薄膜,而被乙醇处理之后,非极性溶剂变得能畅通无阻地通过;并且还发现,不同乙醇含量的乙醇-水的混合溶剂能对薄膜的这种“开关”大小程度能起到有效的调控作用。基于此,我们利用这种薄膜对均匀乳液进行了有效地分离,一定程度上实现了油水分离的应用。另一方面,我们利用另一种纳米结构作为结构基元来构建薄膜,即氧化石墨烯(GO);由于GO结构中包含有sp2杂化的π电子体系和sp3杂化成分,于是当以阳离子修饰之后,GO纳米片与阳离子之间将以阳离子-π相互作用力结合,使得阳离子被固定在薄膜表面和内部的纳米片之间;得到的这种薄膜与纯的GO薄膜相比,其对有机溶剂的通透性表现出截然不同的现象:这种薄膜对于不同的有机溶剂表现出不同的透过速率;并且醇类不能透过此薄膜,而芳香性溶剂却可以透过此薄膜,这是因为薄膜中嵌入的阳离子与溶剂中的芳香环的π电子体系以阳离子-π作用力结合之后,层与层之间的阳离子逐渐导通的结果。基于此实验结果,这种薄膜还被成功地应用于膜反应器中,对一系列酯化反应的连续进行起到了良好的促进作用,这一应用在促进化学反应的正向进行进而提高化工产品生产效率等重大课题中具有巨大的潜力。
[Abstract]:As the two most important weak interaction forces in non-covalent bond, hydrogen bond and cationic 蟺 interaction force, their energy is only 10 percent or even tens of percent of the energy of covalent bond. Therefore, many molecules usually have enough energy to destroy this weak interaction. As a result, such weak interactions are often easily destroyed and easily re-formed. In this paper, based on the weak interaction between these two kinds of noncovalent bonds, on the one hand, we have constructed a kind of macroscopical thin films by using 伪-MnO2 and V_2O_5 of super long one-dimensional nanostructures as structural primitives, respectively. Because of the exposed oxygen atoms (hydrogen bond receptors) on the surface of the structural unit, such thin films are easily bound to hydrogen bond donors in foreign solvents, so that the groups (alkyl) at the other end of the hydrogen bond donor are exposed to the surface of the film. Therefore, when the films are alternately treated with different hydrogen bond donor solvents, the surface of the films will be alternately covered by different groups. Because of this, when we wash the film separately with water and ethanol, we find that the permeability of the film to non-polar organic solvent will be greatly changed: after water treatment, the non-polar organic solvent can not penetrate the film. After being treated with ethanol, the non-polar solvent can pass through unhindered. It is also found that the mixed solvent of ethanol and water with different ethanol content can play an effective role in regulating the size of the "switch" of the film. Based on this, we used the thin film to separate the homogeneous emulsion effectively, and to some extent realized the application of oil and water separation. On the other hand, we use another kind of nanostructure as the structure unit to construct the thin film, called graphene oxide (GO);). Because the structure of GO contains sp2 hybrid 蟺 electron system and sp3 hybrid, when modified by cationic, the cationic-蟺 interaction between GO nanoparticles and cations will be combined. The cations are fixed between the surface of the film and the inside of the film. Compared with the pure GO film, the film shows a different permeability to organic solvents: the film exhibits different transmittance rates for different organic solvents; And alcohols do not pass through the film, but aromatic solvents do, because the cation embedded in the film binds to the 蟺 electron system of the aromatic ring in the solvent by cationic-蟺 force. The result of the gradual conduction of cations between layers. Based on the experimental results, the film was also successfully used in the membrane reactor, which played a good role in promoting a series of esterification reactions. This application has great potential in promoting forward chemical reaction and improving the production efficiency of chemical products.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ051.893

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