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Swelling, Exfoliation and Application of Layered Organic Material

Author: XuZuo
Tutor: LiLiangBin
School: University of Science and Technology of China
Course: Synchrotron Radiation and Applications
Keywords: two-dimensional organic nanomaterials oligo(p-benzamide) swelling exfoliation polymer nanocomposite materials
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Type: PhD thesis
Year: 2013
Downloads: 133
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Abstract

Recently, two-dimensional organic nanomaterials have attracted extensive investigations and applications in novel catalysts, information storage and optoelectronic devices due to their unique property as compared to two-dimensional metal or inorganic nanomaterials, such as flexibility, absence of grain boundaries and minimal concentration of charge traps. However, due to the weak intermolecular interaction in layered structure of organic materials, where van der Waals force and hydrogen bond are generally the main force to glue molecules together, as compared with metallic and ionic bonds in metal and inorganic nanomaterials, many kinds of preparation methods of two-dimensional metal and inorganic nanomaterials cannot be used to prepare two-dimensional organic nanomaterials. To date, self-assembly is still the most effective and wildly used approach to prepare the two-dimensional organic materials. However, this time consuming and low-yield process limits the application of layered organic materials. Therefore, it is of great importance in both research and application to develop facile method to prepare two-dimensional organic nanomaterials.In this thesis, two different series of linear molecules based on oligo(p-benzamide) were designed and sythesised. Through re-crystallizing these target molecules, a variety of layered organic materials can be obtained. After evaluation of dispersion property of layered material in water, S6was selected as a model system to study the swelling and exfoliation of layered organic material. The main research work and conclusion are depicted as follows:1. Two series (Sn and SnF) of linear oligo(p-benzamide) molecules were designed and sythesised via a controlled solution polycondensation and characterized by NMR and MS spectra. Through a simple re-crystallization method, all molecules can form layered material as confirmed by small angle X-ray scattering. The exfoliation of all layered materials was tried via dispersion of layered materials in water with ultrasonic assistance.2. Through a simple re-crystallization method, layered S6with well oriented layer-stacking structure can be obtained. The dynamic swelling and deswelling of layered S6were monitored by simultaneous small angle X-ray scattering/wide angle X-ray diffraction measurements. Well oriented layers of S6can be partitioned upon intercalation of water molecules, while in-plane morphology was retained during swelling. By volatilization of water molecules from gallery or deswelling of swollen S6, the swelling process is found to be reversible as demonstrated by the restoration of original structure after deswelling. In addition, the interlayer separation is adjustable through controlling the extent of hydration of the sample by adding or volatilizing water.3. According to the results of swelling process, the probability of exfoliation of layered S6was demonstrated. With a simple dispersion in water, layered S6can be successfully delaminated into monolayer nanosheets. This method is a green, time-saving and low-cost approach and possibly is the first achievement of exfoliation of three-dimensional multilayer organic material into two-dimensional organic materials. This achievement may provide a new strategy to prepare two-dimensional organic nanomaterials without using any substrates or templates, which are required in conventional and widely used self-assembly route.4. Based on S6nanosheets obtained from exfoliation of layered S6, the preparation of PVA nanocomposites with S6nanosheets as nanofiller were achieved via a simple water solution processing. After homogeneous dispersion of S6nanosheets in PVA matrix, the mechanical property of PVA nanocomposites were significantly enhanced as compared to pure PVA. A64%increase in tensile strength and a63%improvement of Young’s modulus are achieved by addition of7wt%of S6nanosheets. Furthermore, the improvement of the thermal stability of PVA nanocomposites can also be achieved via addition of S6nanosheet.

Swelling, Exfoliation and Application of Layered Organic Material

Abstract

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