Based On The Aggregate Of Keggin Type Heteropoly Acid Surface Modification Preparation Of Pam Microgels Structure Microspheres

Heteropoly acid catalysts for epoxidation of olefins and deep desulfurization get popularly attention.This kind of reaction based on biphase catalysis sensitize to the dispersion of dispersed phase.Compounding the heteropoly acid salts and the quarternary ammonium salts surfactant plays apositive role to increase the dispersion; however, there are some problem that cannot be resolvedsuch as the product purification and the recovery of catalyst. In this study, we based on thestructure of micelle and construct the dispersed phase that can be reused where the aqueous phaseform a unified integral by microgels. Based on this research thinking, we study the in-situpolymerization of heteropoly acids which can be polymerized happened on the surface of microgels.Based on the idea mentioned above, the research in this thesis includes the following four parts.(1) Under different acid environment, the sodium silicate and the sodium tungstate willchemical combine and generate silicotungstic acid in different crystallographic form. So, they -silicotungstate: Ks[γ-SiW10O₃₆]-12H₂O could be produced by adjusting their pH. Thissilicotungstate was characterized by X-ray diffraction (XRD) and ultraviolet spectrum (UV).(2) Add the methyl cyanide solution of MAPTMS into the acid solution ofKs[γ-SiW10O₃₆]-12H₂O, make MAPTMS hydrolyze and condensation, then combine they -silicotungstate with Si-O-Si to produce the hybrid materials which can be polymerizedsilicotungstic polyoxometates: Na₄{Ks[γ-SiW10O[CH₂=C(CH₃)CO₂SiO]₄}, To characterizePOM with FT-IR, the POM still have the characteristic peak of W-0 bond similar to silicotungsticacid and the infrared characteristic peak of long chain functional group like MAPTMS. So, thestructure of POM has the long chain of MAPTMS which is drainage on this side; and the Kegginstructure of silicotungstic acid on the other side, which is hydrophile. At the same time, thedrainage side has polymerisable C=C, it's a kind of polymerisable surfactant.(3) Use the swelling effect of microgel to take PAM microgel as the template; first to infusePAM with the water solution of POM or TMEDA, and then put the PAM in TMEDA, APS orPOM and APS, the core/shell type combined microsphere of PPOM-PAM will be created by thetwo methods. We have alternated the concentration of initiators POM, TMEDA, and also changethe reaction time and the concentration of salt. And then, PPOM-PAM microspheres arecharacterized by Scan Electronic Microscope (SEM) and FT-IR. The result shows that thePPOM-PAM composite microspheres can be prepared by both ways. The PPOM microspheresincrease with the prolonging of reaction time. Comparatively, first to infuse PAM with the water solution of TMEDA, and then put the PAM in POM and APS, the PPOM-PAM microspheres havemore PPOM microspheres on the surface. Increasing the concentration of reactant can increase thenumber of PPOM microspheres on the surface; and the affect of salt solution make the size ofPPOM microspheres minish. The composite microspheres got by the two methods have thecore/shell type. We can control the surface morphology by the preparation conditions.(4) The status of POM in the water solution and the internal surface look of PPOM-PAMcombined microsphere are analyzed by the methods like fluorescence spectrum and SEM, and thenthe possible formation mechanism of PPOM-PAM is concluded. The mechanism is like this: PAMmicrogel could be the container of TMEDA water solution. When the PAM microgel has storedsome certain quantity of TMEDA water solution, dipped the water solution with POM, APS andTMEDA in it. POM will form micelle in the water solution, and the C=C double bond tail is inner,the silicotungstate heteropolyacid outside. APS can initiate the double bond polymerization, andthen by the consumption of TMEDA, which stored inside PAM will spread to the surface of themicrosphere, and enter the micelle of POM, make the combine reaction continue going. So, thepolymerized PPOM microspheres will assemble on the surface of PAM microgel.