The Prepartion And Structure Of Polymer/Silica Nanocomposite Emulsion

The application of waterborne resins are the inevitable development in the coating industry and adhesive industry. There are many prepared technique such as emulsion polymerization method and post-emulsification technique used to obtain the waterborne resins, however, the properties of the waterborne resins are lower than that of the solvent-based resins.Recently, a number of waterborne polymer/silica nanocomposite emulsions had been synthesized using various techniques such as in situ emulsion polymerization and blending method, since inorganic nanosilica particles could improve some performances and even endow polymers with novel properties. However, the previous studies mainly focused on the morphology and properties of the coating under ambient temperature, very few studies have been concerned the film formation of these nanocomposite emulsion under more than 100℃.In ths dissertation, the polymer/silica nanocomposite emulsions were prepared by in situ surfactant-free emulsion polymerization, blending method and post-emulsification technique using nanosilica as a "Pickering" emulsifier. When the nanocomposite emulsions were dried to form a film at a certain temperature, the 2D surface porous structure, "inverse opal" structure and adhesives were fabricated by adjusting prepared technique, monomer composites, nanosilica content, temperature of forming film and etc.. A macromolecules Phytic acid-polysilsesquioxanes was prepared by silylated phytic acid reacting with MTES and TEOS, which had significantly excellent corrosion resistance.All the research content and results are as follows:(1) This paper presents a novel and facile method for the fabrication of nanocomposite films with ordered porous surface structures. In this approach, a water-borne poly(styrene-co-butyl acrylate-co-acrylic acid) /silica nanocomposite emulsion was synthesized in situ emulsion polymerization using 3-allyloxy-2-hydroxy-1-propanesulfonate as a polymerizable surfactant. When this emulsion was dried to form a film at a certain temperature, an ordered porous structure could be directly obtained on the surface of the nanocomposite film. This was probably duing at a fast evaporation rate of water, silica particles transform into hard silica framework via the condensation of silianol groups, meanwhile, soft polymer particles can easily collapseand immigrate into the voids existing in silica framework to form ordered porous structure on the surface of the nanocomposite film. SEM, TEM and AFM were employed to observe the morphology, XPS and particle analyzer were used to analyze the surface composition of the ordered porous nanocomposite film, and the particle size, respectively.(2) An one-step strategy to fabricate large-scale inverse opal photonic crystals has been proposed, in which a nanocomposite emulsion composed of polymer latex and colloidal silica is blended first, and then forced-drying on a substrate under relatively high temperatures to directly obtain a film with three-dimensionally array of ordered pores. This strategy is really simple and inexpensive: Neither complex processes nor special equipments are needed, as large as several square meters inverse opal photonic crystal can be fabricated on any substrates without any templates. And the backbone of the inverse opal is composed of organic and inorganic phases, thus the optical, electric, magnetic and mechanical properties of the inverse opals can be modulated. This technique presents a new paradigm in the preparations of inverse opal photonic crystals.The particle size of polymer particles, surface components, morphology and optical properties of photonic crystal films were investigated by FTIR, ATR-FTIR, XPS, TEM, SEM and Reflection spectra. The PCs films have very beautiful iridescence phenomena and regular periodicity. The reflectance spectra of PCs stimulated by layered-KKR method has a very good agreement with the experimental results.(3)Stable waterborne silylated polymer latex was obtained via post-emulsification process by utilizing reaction between hydroxyl groups on the surface of nanosilica and alkoxysilyl groups on the molecular chain of the silylated polymer, only a small quantity of surfactant was needed. A large quantity of nanosilica was adsorbed on the surface of the silylated polymer latex particles. The nanosilica not only can serve as a Pickering emulsifying agent to stabilize the polymer latex particles, but also can inhibit the self-crosslinking of the silylated polymer in water and improve the mechnics properties, aging resistance properties.The structure, stability and rheological behavior of the silylated latex was investigated by FTIR, particle size analysis, SEM, respectively. The smaller the colloidal silica size was or the more the silica content was, the greater the storage modulus was at low strain amplitude, indicating a stronger interparticle interaction and a solidlike viscoelastic behavior of the emulsion. This rheological behavior can be explained by the formation of the reversible particulate network in the emulsion.(4) Waterborne nanocomposite adhesives were obtained via silylated polymer/silica nanocomposite emulsion cured with nanosilica stemming from tetraethyl orthosilicate (TEOS), silica sol and/or fumed silica powder. Effects of TEOS content, silica sol content and the type and content of fumed silica on the shear strength of the adhesive were investigated using a scanning electronic microscope and an electronic instron tester and the strengthening mechanisms of different silica source were discussed. Colloidal silica particles was less efficient than fumed silica particles for reinforcing the nanocomposite adhesive but can increase the shear strength of hydrophobic fumed silica embedded adhesive. Comparing the adhesives with the hydrophilic fumed silica (HS-5) or the extremely hydrophobic fumed silica (TS-720), the adhesive with moderate hydrophobic fumed silica (TS-610) had the highest shear strength. It seemed that TEOS, silica sol and fumed silica played crosslinking, dispersing (for fumed silica) and reinforcing roles on waterborne adhesive, respectively.(5) The high-molecular-weight phytic acid-polysilsesquioxane was successfully synthesized via sol-gel process using silylated phytic acid reacting with MTES and TEOS without any low molecular acid, the molecular weight of phytic acid-polysilsesquioxanes was more than 50000. Phytic acid served as not only catalysts but also reactant and chelating agent, which was in-situ incorporated with polysilsesquioxane chain uniformly. GPC, ¹³CNMR, ²⁹SiNMR, XPS, Raman, SEM, electro-chemical techniques were used to investigate the correlation between the microstructure and property of PAP, TAP and HCP. PAP could form a compacting protective film because of strong chemical interaction between metal substrate and phytic acid-polysilsesquioxane, which had significantly better corrosion resistance compared to tannin-catalyzed polysilsesquioxane and HCl-catalyzed polysilsesquioxane.