Functional Particles: Synthesis, Structural Control, And Properties Investigation

In this thesis, the main attention is paid to the controlled fabrication and related performances of functional composite particle and hollow particles. Under the guidance of colloidal theory, the pursuit of specific target is to develop simple, effective and controlled preparation methods. Herein, several new, facile and controlled strategies that afford fine control over the size, composition, structure, and property of functional particles have been proposed. Centering on the above contents, the main works in this thesis cover the following five aspects:(1) Controlled Preparation of Monodisperse Core-Shell PS/PANi Composite Particles. By means of "Swelling-Diffusion-Interfacial Polymerization Method" (SDIPM), polyaniline (PANi) was successfully coated onto uncharged, micrometre-size polystyrene (PS) particles, or even positively charged PS particles. Based on thermodynamic principle, the distribution, diffusion and interfacial polymerization of aniline monomer were well controlled in colloidal system, and thus, the PANi overlayer was formed readily on the surface of substrate particles. This method affords much more effective control over the structure and morphology of the resultant composite particles by simply changing the aniline/PS weight ratio. These results not only break the traditional thinking that PANi cannot be coated onto positively charged substrates, but also demonstrate the possibility of obtaining the uniform PANi overlayer on the surface of micrometre-size PS particles, especially in the case of high concentration of aniline.(2) Controlling the Structure and Morphology of Organo-silica/PS/PANi Composite Particles. By virtue of a facile and ingenious strategy, multilayer and conductive organo-silica/PS/PANi composite particles were successfully prepared. First, organo-silica/PS core-shell composite particles were synthesized by seeded emulsion polymerization and vinyl groups located on the surface of organo-silica nanoparticles were used to induce in situ polymerization of styrene. The influence of the route of the addition of styrene on the morphology of organo-silica/PS composite particles was investigated. Then, the coating of organo-silica/PS composite particles with PANi was achieved by virtue of the SDIPM. The structure of multilayer and conductive composite particles can be well controlled by simply changing the weight ratio of aniline/PS. The whole preparation process was monitored by transmission electron microscope, scanning electron microscope, Fourier transform infrared and Raman spectroscopy, dynamic light scattering, and thermogravimetry.(3) Thermodynamically Driving Self-assembly for Fabricating Various Functional Polymer Composite Particles. In the system, the PS host particles were synthesized by dispersion polymerization, and no longer went through any surface pretreatments. By changing the medium, the PS host particles shifted into the metastable state due to the increase of interfacial tension against the aqueous medium. Subsequently, the thermodynamic effect is utilized as a unique driving force for coating of PS host particles with different functional guest units, for example, zero-dimensional nanoparticles, one-dimensional nanorods or nanotubes and two-dimensional nanooverlayers, to obtain a variety of functional composite particles. These plentiful results fully demonstrate the thermodynamically driving self-assembly for fabricating various functional composite particles is facile and versatile. In addition, there exists the thermodynamically driving effect in such cases of synthesizing the corresponding guest units, for example, noble metal nanoparticles or conducting polymers, in the presence of the PS host particles. In other words, the self-assembly process is further simplified to be completed in one-step.(4) Thermodynamically Driving Self-assembly for Fabricating Raspberry-like Gold Nanoparticles-coated Polystyrene Composite Particles in One-step. In the system, the gold nanoparticles (AuNPs) forming in the presence of PS microspheres play the role of the stabilizer, and thus adhere onto the surface of metastable substrate microspheres that can make the colloidal system have the lowest Gibbs free energy. The whole preparation process can be summarized as follows. The HAuCl4 aqueous solution was first heated up to boiling. Then, the PS microspheres and trisodium citrate solution were added in turn to the above-mentioned solution. Once the HAuCl4 was reduced to generate hydrophilic AuNPs, they were willing to attach upon the metastable PS microspheres to form the raspberry-like composite particles. Based on the preparation process and reaction mechanism, the morphology of the resultant composite particles can be easily controlled by adjusting the type and amount of reductant or the concentration of PS microspheres. In addition, the AuNPs-coated PS composite particles exhibit the good surface-enhanced Raman scattering and catalytic performances.(5) "Self-stable and Self-consumptive Template Method" for Controlled Fabrication of Hollow Silica Microspheres. The hollow silica microspheres were successfully prepared in a simple and green aqueous system, containing only two components, tetraethoxysilane (TEOS) as precursor and ammonia as catalyzer, by means of "Self-stable and Self-consumptive Template Method", which was carried out by adopting a novel process of feeding of TEOS. The whole preparation process can be summarized as follows. First, the first part of TEOS was slowly and continuously injected into an ammonia solution (stage 1); second, the residual part of the precursor was added collectively to the reaction system (stage 2). Based on the preparation process and reaction mechanism, rapid formation of silica shell on the oil-water interface should be a key effect on successfully fabricating hollow microspheres. Thus, several factors influencing the rapid formation of silica shell, involving the amount of TEOS added in stage 1, reaction temperature and concentration of ammonia, were systematically studied. The resultant results fully proved that the previous discussion on the formation mechanism of the hollow silica microspheres was reasonable, and indicated that the morphology of the hollow silica microspheres was governed by the above-mentioned three factors.