Preparation Of Three-Dimensional Ordered Porous Materials Based On Polymer/Silica Nanocomposite Latex

Organic-inorganic composite materials combine the advantages of the two components, and have novel structures and properties. Combination of polymer latex with SiO2 particles is an important strategy to improve the properties of polymeric materials. Recently, researchers have done a lot of work on the preparation of polymer/SiO2 nanocomposite latex, morphology of composite particles, and properties of composite coating. But most of the researches only focus on the above three fields, and on the film-formation at ambient temperature. In this dissertation, when polymer/SiO2 nanocomposite latex was forced-dried at different high temperatures,3-dimensional-ordered-macroporous (3-DOM) film and surface morphology gradient can be directly obtained, respectively. We also use the nanocomposite latex as binary particle system, and prepared hierarchically ordered porous carbon via in-situ self-assembly of polymer spheres and silica particles with carbon source. All the research content and results are as follows:(1)A series of colloidal polymers with various Tg, composition, and sphere size were synthesized by surfactant-free emulsion polymerization and dispersion polymerization methods and then blended with colloidal silica particles to obtain stable polymer/silica nanocomposite latexes. When these nanocomposite latexes were forced dry at relatively high temperature (e.g.,110℃) for 2 h, a 3-DOM structure was directly obtained. Neither complex processes nor removal of any templates like in a templating method was needed. Therefore, it is really feasible, inexpensive, and environmentally friendly. More importantly, this process can be used for a large-scale fabrication of ordered porous polymer films. However, the strong repulsive force between polymer sphere and colloidal silica particles is necessary to successfully prepare the stable nanocomposite latex and then the ordered porous film. In addition, we investigated the effects of some key parameters, e.g., polymers with various glass transition temperature (Tg), composition, hydrophilic component, structure and sphere size, solvent with different volatility and silica particle size on the formation of ordered porous film, and tried to really understand the formation mechanism of this ordered porous structure via the forced-drying strategy, these ordered pores should form from the top surface and then propagate layer by layer from the top surface to substrate. The films are typical faced-centered-cubic structure, and show structure colors, and can be used as solvent sensors.(2) The second part presents a novel and feasible approach for fabrication of morphological gradient surfaces based on the film-formation of nanocomposite polymer latex. In this method, when the polymer latex with relatively low Tg was blended with colloidal silica and then dried at certain temperatures, a morphological evolution with deeper pores from the center to the edge could be directly obtained on polymer surface. Neither careful control of experimental conditions nor any complex processes are needed. The Tg of polymer, the silica content, the solvent and the drying temperature have significant influences on this surface morphology. The film-formation mechanisms at different drying temperatures are also discussed.(3) The third part presents an one-pot method to synthesize hierarchically ordered porous carbons with interconnected macropores and mespores, via in-situ self-assembly of colloidal polymer and silica spheres with sucrose as carbon source. Compared with other techniques, this procedure is veritably simple, neither pre-synthesis of the macropore/mesopore or crystal templates nor additional infiltration is needed, the self-assembly of polymer spheres into crystal template and the infiltration are finished in-situ in the same system. The sizes of macropores and mesopores can be independently tuned by the sizes of polymer and silica spheres, respectively. The obtained bimodal porous carbons have large BET surface areas, large pore volumes, and partially graphitized frameworks. And they show very good supports of Pt-Ru alloy catalyst in direct methanol fuel cell.