Dissertation > Excellent graduate degree dissertation topics show

Preparation and Characterization of Organic/Inorganic Core-Shell Materials

Author: LiZuo
Tutor: GaoGe
School: Jilin University
Course: Polymer Chemistry and Physics
Keywords: Emulsion polymerization sol-gel SiO2 PS OMC core-shell structure
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 341
Quote: 0
Read: Download Dissertation

Abstract


In recent years, there has been increasing interest in core-shell materials due to its potential in developing novel materials with unique functions. The exterior coating structure is very useful in many applications in order to enhance the stability of dispersions, to protect the particles from interaction with surrounding medium, and to endow the core optical, conductive, magnetic, adsorptive, and surface reactive properties. Polymer organic-inorganic core-shell particles attract scientists’attention because it realizes the molecular scale fabrication. Combining the properties of organic and inorganic components, this kind of materials has excellent and special capability as compared to its components. The inorganic shell can improve the internal domain thermal stability, mechanical strength and scratch resistance. The latex core exhibits elasticity and film formation ability. The latex coated with inorganic matter imparts the core-shell particles with improved chemical and physical properties, creating synergistic effects.Many studies for coating process have been proceeded comprised of in situ deposition as well as layer-by-layer （LbL） technique. In situ deposition is to prepare the core-shell particles by controlled precipitation of inorganic precursors onto the core domain. The second approach, LbL technique is versatile method to synthesize core-shell materials. It’s based on electrostatic interaction between particles, the species having opposite charge with core and absorbing on the surface of the core. The coated particles subsequently centrifuged and washed could be deposited in order to obtain the desirable coating thickness. Disadvantages of this technique are not only the time-consuming sequential polyelectrolyte deposition cycles and purification steps, but also the incorporation of redundant polyelectrolyte into shell. Chemical coprecipitation is first to immerge the polymer colloid with inorganic salts, next, by using in situ reaction, the organic core were coated with inorganic shell.Silica has many advantages:ⅰ) It is chemical inert and optical transparent;ⅱ) The silanol groups on the shell are available for further surface modification;ⅲ) Silica can be easily doped with fluorophores and dyes. These specific properties are utilized for technological application from medicine, paints, inks, to fillers. Titania is also a good kind of inorganic material, and it can be used as catalysts, white pigments etc. Here, we mainly study polymer-inorganic core-shell materials, specifically the silica coating.Here, PS/SiO2 and OMC/SiO2 core/shell nanoparticles were synthesized by two different methods. In the second chapter, monodisperse polystyrene latexes were prepared by emulsion polymerization. Then tetraethoxysilane （TEOS） was added to this system in acid condition using sol-gel method, and the obtained polystyrene latexes were employed as the template. The electrostatic interaction at the surfactant/inorganic interfaces governed the assembly process. As a result, there was a layer of about 17 nm silica at the surface of polystyrene latex. The polystyrene-silica particles were analyzed by TEM、SEM、DLS、FT-IR and DSC. In addition, effect of the amount of surfactant on diameter and conversion of polystyrene latexes was investigated in detail.In the third chapter, OMC/SiO2 core/shell nanoparticles were prepared with a novel method. First, SiO2 shell precursor was prepared with a sol-gel method. It contained a large amount of OH groups, which offers versatile possibilities for condensation polymerization under alkaline condition. Then an O/W emulsion was produced under the stirring of a homogenizer. After the outer surfaces of the emulsion droplets are solidified by the condensation reactions between the surface silanols, they may serve as self-templates. Subsequently, the un-reacted precursor within the emulsion droplets becomes solidified onto the templates as shell, while the core compounds stay inside as core, producing core-shell nanoparticles. In the last, the mechanism of this method for forming core-shell nanoparticles was discussed. The obtained core/shell particles were analyzed by TEM、SEM、DLS、FT-IR and UV.

Related Dissertations

  1. Preparation and Photocatalytic Properties for Water Decomposition of Titanate Photocatalyst,O643.36
  2. Preparation of ITO Quai-1D Nanostructures by Sol-Gel Method Combined with Porous Anodic Aluminum Oxide Template,TB383.1
  3. Hydrothermal Synthesis of Oxide Hollow Spheres,TB383.4
  4. Preparation and Electrocaloric Effect of BaxSr1-xTiO3 Ferroelectric Thin Films,TB383.2
  5. Multi-walled Carbon Nanotubes Au _AT_ of Pt, Au _AT_ of Pd core-shell structure of the catalyst preparation and electrochemical properties of,O643.36
  6. Preparation and Characteration of Composite Microspheres with Dual-, Triple- Responsive Properties,O631.3
  7. Preparation and Performance of V2O5-WO3/MOx/Cordierite Catalyst Modified with Cu、Mn、Ce for DeNOx,X701
  8. Study on Properties of Ce、Co、Ni/V-W/TiO2 Modified by Composite Sol for Selective Catalytic Reduction,X701
  9. Preparation and Characterization of Polymer Micro/Nano Fibers by Laser Melt Electrospinning,TQ340.64
  10. Modification for PVA-Based Composite Packaging Material with Nano-SiO2 and Its Influence on Fresh Preservation Effect of Salted Duck Eggs,TS253.46
  11. Iron, lanthanum -doped nano TiO \u003csub\u003e 2 \u003c/ sub\u003e Preparation and photocatalytic properties,O614.411
  12. Synthesis of 1,4-Butynediol from HCHO and C2H2 Over CuO-Bi2O3/MgO-SiO2,TQ223.162
  13. Lithium anode material calcined alumina crucible Development,TQ174.6
  14. A class with a convex top semilinear elliptic boundary value problem research,O175.8
  15. Core-shell polymer microspheres synthesis, modification and application,O631.3
  16. Study on Preparation and Properties of Polyimide/SiO2 Hybrid Films,TB383.2
  17. Preparation and Characterization of Multifunctional Fe3O4/ZnO/SiIO2 Nanocomposites,TB383.1
  18. Research on Novel and Highly Efficient Modified Hybrid CrOx-B/SiO2 Catalyst for Ethylene Polymerization,TQ325.12
  19. Study on Corrosion Resistance and Condensation Property of Ni-P/Nano SiO2 Composite Coatings,TG174.4
  20. Preparation and Characteristic of BiFeO3 /Bi3.25 La 0.75 Ti3O12 Multiferroic Bi-layer Films,O484.4
  21. Preparation and Properties of Platinum-based Catalysts for Potential Use in PEMFCs,TM911.4

CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Special structural materials
© 2012 www.DissertationTopic.Net  Mobile