Synthesis, Characterization And Mechanism Of High Performance Fluorinated-Acrylate, Silicaon And Acrylate Copolymerization Latex

Fluorine-silicon-acrylate copolymers are one kind of materials with high performance including excellent weather resistance, thermal and chemical stability, and particularly the ultra-low surface free energy, which make the surface water-repellent, oil-repellent and self-cleaning. Fluorine-silicon-acrylate copolymers are widely used as coating, textile finishing, leather finishing and so on. The study on the preparation of fluorine-silicon-acrylate copolymers is remarkable and worthwhile. As an important method for the preparation of high performance fluorine-silicon-acrylate copolymers, emulsion polymerization has many advantages, such as the high polymerization rate, safety and no pollution. In present dissertation, high performance emulsions of polymers copolymerized by fluorinated-acrylate, silicone and acrylate were synthesized by different emulsion polymerization techniques including the seeded emulsion polymerization and the miniemulsion polymerization, and the structures, properties and the application behaviors of the emulsions were studied. Furthermore, the kinetics and the nucleation mechanism of the cationic ring-opening miniemulsion polymerization of D4 were systemically explored. The main research works are as follows:1. The synthesis of fluorine-containing latex with core-shell structure and the preparation of coatings with high hydrophobic surfaces.A pivotal question in the synthesis of fluorine-silicon-acrylate copolymers is how to minimize the amount of fluorinate monomers. In this paper, the latex particles were designed with core-shell structures and synthesized by semi-continuous seeded emulsion polymerization. The latex core is composed with low Tg poly(methyl methylacrylate-butyl acrylate) (P(MMA-BA)). The latex shell is composed with high Tg P(MMA-BA) containing vinyl tris(β-methoxyethoxy) silane (A-172) and dodecafluroheptyl methacrylate(DFMA). A-172 is serving as the crosslinking monomer. DFMA is the functional monomer which provides the anti-water properties. The core-shell latex has been characterized by various methods, such as fourier-transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), the X-ray photoelectron spectroscopy (XPS), a video-based contact angle measuring device and atomic force microscope (AFM). The result shows that the surface hydrophobic property characterized by the values of advancing contact angle and receding contact angle for water, were dramatically improved with low amount of DFMA. Coatings prepared by the synthetic latex with different DFMA and A-172 content were compared and the antifouling capability of the coatings were analyzed. It was found that the anti-fouling capability was improved with the increase of hydrophobic property.2. The synthesis of polysiloxane latex grafted by F-containing acrylate via a two-step miniemulsion polymerization method.The fluorine-containing polysiloxane latex is used as multifunctional textile finishing, which provides the textile with pleasant softness and water-repelling properties. However, the low solubility of cyclosiloxanes and fluorinated monomer in water make them unstable in conventional emulsion polymerization. In this dissertation, a fluorine-containing polysiloxane latex were synthesized via two-step miniemulsion polymerization:vinyl groups were introduced into the polysiloxane by ring-opening copolymerization of octamethylcyclotetrasiloxane (D4) and tetravinyltetramethylcyclotetrasiloxane (D4V) in miniemulsion, then the fluorinated monomer(DFMA) were grafted onto polysiloxane by radical copolymerization. The effect of the content of D4V and DFMA on the structure and properties of the emulsion was investigated. The fluorine-containing polysiloxane latex, prepared with appropriate content of D4V and DFMA, is of high performance on the softening and water-repelling properties when it is utilized as a finishing of textile. A comparative study on the conventional emulsion polymerization and miniemulsion polymerization of the polymerization was also carried out. The result shows that the miniemulsion copolymerization of D4/D4V has many advantages, such as the higher polymerization rate, lower emulsifier concentration and better stability. 3. The study on mini-emulsification method and the stability of the correspondingly miniemulsions.The preparation of monomer miniemulsion is the key step in the miniemulsion polymerization. In this dissertation, D4 was chosen as the model monomer and the effects of preparation methods were systemically studied by static multiple light scattering (MLS) and dynamic laser scattering (DLS) technique. Monomer miniemulsion of D4 were prepared by three different devices, rotor-stator system, sonifier and high-pressure homogenizer, respectively and the the stability of monomer miniemulsions were estimated. The results show that the monomer miniemulsion prepared by high-pressure homogenizer was most stable. Furthermore, the effect of homogenization condition and the recipes on the droplet size and distribution (DSD) of monomer miniemulsion were studied in detail. The influences of the droplet size of monomer miniemulsion, the concentration of DBSA and the temperature on the stability of monomer miniemulsion were also discussed.4. Kinetic study on the cationic polymerization of D4 in miniemulsion.The cationic polymerization of D4 in miniemulsion is of its unique kinetic and thermodynamic feasures. A kinetic study on the ring-opening polymerization (ROP) of D4 in miniemulsion is presented in this dissertation. The polymerization was initiated by dodecylbenzenesulfonic acid (DBSA) which also served as the surfactant (inisurf). The influence of the size of monomer droplet and the concentration of DBSA on the polymerization rate were studied. With the main place for the ROP of D4 confirmed at the oil/water interface, a three-layer interface model was proposed to analyze the distribution of molecules in the interface and the effects of the DBSA. A kinetic equation was then developed based on the interface model. In the equation, the polymerization rate (Rp) was related to the initial monomer concentration ([D4]0), the droplet radius (r), the coverage of DBSA on monomer droplets surface (χ). The polymerization rate can be predicted from the kinetic equation after all the parameters determined. Finally, the equation was verified by the good accordance of the predicted polymerization rate data with the experimental results under different polymerization conditions.5. The study on the nucleation mechanism in the cationic polymerization of D4 in miniemulsion.The miniemulsion polymerization of octamethylcyclotetrasiloxane (D4) was carried out and the particle sizes during polymerization were monitored by DLS technique. Although the monomer miniemulsion was homogenized very well by a high-pressure homogenizer, the particle sizes kept on decreasing with the increase of the monomer conversion in the polymerization, which indicated the occurrence of new particles. Considering the hydrophilicity of the components in the miniemulsion system, a homogenous nucleation of oligomers was likely to happen besides the primary droplet nucleation mechanism. The oligomers nucleation mechanism was justified by the linear relationship between the natural logarithm of the particles diameter (lnd(t)) and the natural logarithm of conversion of monomer(lnf(t)). In addition, the influence of the inisurf concentration and the polymerization temperature on the ratio of the oligomers entering water phase to all the polymers produced were discussed.