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Preparation of Different Morphology Particles via Miniemulsion Technology and Their Properties

Author: LuWei
Tutor: WuLiMin；Elodie Bourgeat-Lami
School: Fudan University
Course: Materials Physics and Chemistry
Keywords: Miniemulsion droplets CdS hollow spheres Dodecyl mercaptan Miniemulsion Polymerization mechanism Organic - inorganic composite microspheres Silane coupling agent Hybrid asymmetric particles
CLC: O631.5
Type: PhD thesis
Year: 2009
Downloads: 303
Quote: 1
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Abstract


Miniemulsion technology development and now has 30 years of history, the droplet nucleation mechanism, the rate of polymerization prepared latex particles and good uniformity characteristics of the decision miniemulsion technology in many areas larger development, to expand the field of application of the miniemulsion technology has important practical significance and research prospects. Miniemulsion technology in order to expand the application fields of the miniemulsion for the purpose-oriented in the field of cutting-edge research, carried out in miniemulsion droplets as a template to prepare CdS nanocrystalline inorganic hollow spheres using miniemulsion synthesis sulfhydryl of the PSt particles and further preparation of organic - inorganic composite microspheres and the fine emulsion polymerization of PSt-SiO 2 organic - inorganic hybrid asymmetric particle, such as a series of specific research and experimental results are as follows: (1) as a template miniemulsion droplets prepared CdS nanocrystalline inorganic hollow spheres. -Dodecyl mercaptan (DDM), a functional group having a mercapto group as a co-stabilizer, and the lower boiling iso-octane as a fine emulsion of the oil phase prepared functional fine emulsion droplets, then the miniemulsion droplets template synthesis of CdS Nanocrystals hollow microspheres. Although optional droplet soft template, but the hollow microspheres prepared in spherical maintain good and relatively uniform size. DDM has a dual function, on the one hand, as the stability of the stabilizers fine emulsion droplets, adsorption of metal ions other hand, as a functional group, a mercapto group with NaOH under alkaline conditions the reaction of S - , S - metal Cd 2 (Cd (Ac) 2 · 2H 2 O) to form the metal thiolate coated in miniemulsion droplets surface, the adsorbed Cd 2 with the subsequent addition of S 2 - (Na 2 S · 9H 2 O) and of the reaction under the heating conditions of the droplet outer CdS shell is formed. Isooctane CdS formation that is volatile in the process or the subsequent drying out, therefore, can be this simple and effective method is easier CdS Nanocrystals hollow microspheres, compared with the method of preparation of hollow microspheres, the method simple, without template functional process without the use of additional methods out of the template. The CdS nanocrystals size of the hollow microspheres can be adjusted by adjusting the molar ratio of the non-ionic surface active agent with the anionic surface active agent, the wall thickness can be adjusted by controlling the amount of the DDM. EDX, XRD, HRTEM and SA-ED results show that the shell of the hollow microspheres is from the the CdS hexagonal crystal type nano-crystalline composition, and is present in the form of polycrystalline. UV-visible absorption and fluorescence spectroscopy results show the preparation of CdS hollow microspheres with quantum confinement effects, further confirmed the nanocrystalline CdS hollow spheres of housing. (2) the use of miniemulsion technology prepared mercapto functionalized PSt particles, a new way to provide a process for preparing organic - inorganic composite microspheres. Dodecyl mercaptan (DDM) as co-stabilizers, octyl phenol polyoxyethylene ether (CA-897), non-ionic surface active agent is an emulsifier, optional oxidation of KPS / NaHSO 3 redox system as initiator, to prepare a mercapto functional PSt particles. By changing the concentration of the emulsifier, and the type of initiator, the polymerization mode, adding method and the alkaline component added or not conditions of the DDM is the more detailed and systematic study of the kinetics of the process of preparation. Further, use of the strong interaction of the mercapto group and inorganic particles, the prepared organic - inorganic composite material and to explore the interaction between the different functional groups and the inorganic particles, the results showed that, the-S - functional groups and-SH functional group of the inorganic particles with a strong adsorption, while the other functional group such as SO the 4 the 2 - and non-ionic surfactants no adsorption effect of the agent on the inorganic particles. The TGA results further confirm the above conclusion, and be seen by TGA results-SH functional groups may be more than the-S - functional groups on the inorganic particles have a stronger sorption. (3) Based on the technology of the miniemulsion step preparation of a PSt-SiO 2 hybrid asymmetric particles. The organic monomer is styrene (St), and an inorganic precursor tetraethyl orthosilicate (TEOS) is limited caused by phase separation due to heating and polymerization in a fine emulsion droplets micro-reactor, along with of PST particles and SiO 2 the formation of the particle is further strengthened, prior to add fine emulsion droplets in the silane coupling agent γ-methacryloyloxy propyl trimethoxy silane (γ-MPS) enriched in the organic particles and inorganic particles at the connection as a bridge and link them together, the last of PSt-SiO 2 hybrid asymmetric particle. The method of preparation of organic - inorganic hybrid asymmetric particles without going through the process of preparation and modification of the template particles to achieve a one-step synthesis the hybrid asymmetric particles, the method is relatively simple and innovative, creative, prepared by a hybrid an asymmetric particle yield exceeding 40%. PSt-SiO 2 hybrid asymmetric particles PSt particle size by adjusting the fine oil emulsion phase St TEOS is carried out by the mass ratio and the change of the fine emulsion prepared ultrasonic power adjustment. The preparation PSt-SiO proposed based on the experimental results and comparative experiments 2 hybrid asymmetric particle formation mechanism shows that the presence of the silane coupling agent γ-MPS is to ensure that the experiment is successful, the crucial factors. When coated with metallic silver nano colloid asymmetric particle surface, its target molecules with strong surface-enhanced Raman scattering (SERS) effect. In addition, the method also extends swelling - a kind of micro-phase separation theory is applied.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > Polymerization,polycondensation reaction
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