Study On Preparations And Properties Of Polymeirc Microspheres Through Photopolymerization

Photopolymerization is an important synthesis technology in polymer material，andcompared to thermal-initiated polymerization, The typical characteristic ofPhotopolymerization lies in that it can be carried out at low temperature,high reaction rate，energy saving, simple equipment, easy to implement industrial production and so on. With therapid development of global economy，the threats of energy and environment problem areincreasingly serious； Photopolymerization has tremendous advantages on sustainabledevelopment strategy.Polymer microspheres are finding to be increasing applications in various fields, such asmedicines, biotechnologies, electronics, chemical technologies, cosmetics and so on. Variousmethods have been employed to prepare polymer microspheres, such as emulsionpolymerization, suspension polymerization, and dispersion polymerization. However, thesemethods must be proceeded at high temperature by thermal-initiated polymerization, whichare energy-consuming and often difficult to prepare in low temperature. The thesis hasreviewed the photopolymerization technology was applied in the preparation polymermicrospheres. The main contents of this paper are as follows.(1) P(St-g-NIPAAM) microspheres were synthesized through dispersionPhotopolymerization. Taking2,2-dimethoxy-2-phenylacetophenone (BDK) as photoinitiator,PNIPAAM with a vinyl end groupas stabilizer,the mixture of ethanol and water asdispersion medium，P(St-g-NIPAAM) microspheres with narrow size distribution weresynthesized under the irradiation of UV-lamp．The obtained microspheres were characterizedby scanning electron microscopy (SEM) and laser light scattering (LLS). The monodispersionP(St-g-NIPAAM) nanospheres were obtained by UV photo-initiated polymerization of St andPNIPAAM in the ethanol-water media at low UV illumination. The results show that the sizeof microspheres can be controlled by changing the UV illumination, concentration ofmacromoners, and the polymerization temperature.(2) Pd/PNVA-g-PAN/PSt composite microspheres were synthesized successfully.Firstly, PNVA-g-PAN/PSt microspheres were prepared by dispersion photocopolymerizationof acrylonitrile (AN) with styrene (St) in the mixture of ethanol and water using dispersionmedium, PNVA macromonomer as reaction stabilizer. PNVA-g-PAN/PSt microsphereswere characterized FT-IR and1H-NMR. The diameter range of microspheres were controledin range from500-1000nm.Next, palladium nanoparticles were located onto the surfaces ofmicrospheres in the mixture of ethanol and water by in-situ reduction method using PdCl2as metal source and ethanol as reducing agent at90℃. The sizes of PdNPs were around9nmby TEM observations, The weight percents of PdNPs immobilized onto the microsphereswere15to30%, depending on the feed amount of Pd2+ions based on determination of TGA.XRD pattern showed that PdNPs were of face-centered cubic crystal structures. PdNPsshowed high activity and selectivity to catalyze the cross-coupling reaction of iodobenzenewith acrylic acid. (3) Ag/P(St-co-MMA) composite microspheres were synthesized. Firstly,P(St-co-MMA) microspheres were prepared by dispersion Photocopolymerization of Styrene(St) and methyl methacrylate (MMA) in a mixture of ethanol and water(Vethanol/Vwater=7/3) using BDK and polyvinylpyrrolidone (PVP) as the initiator andstabilizer, respectively. The structure of microspheres were characterized by FTIR, The sizeand size distribution of microspheres were characterized by LLS, The shape of microsphereswere characterized TEM. The results show that the size of P(St-co-MMA) microspheres canbe controlled in range from500to800nm. Next, Ag nanoparticles were located evenly ontosurface of the microspheres above. Taking silver nitrate (AgNO3) as metal source, Theultrafine dispersed nanoparticles of Ag can be located surface of the microspheres via thereduction of corresponding silver ions (Ag+) by sodium borohydride (NaBH4) or ultraviolet(UV) light. The composite microspheres were characterized by UV-vis, TEM and X-raydiffractometry (XRD). The composite microspheres had good antibacterial property andphotocatalytic. The composite microspheres on the fluorescent properties of fluorescein (FL)were also investigated. With the increase of Ag nanoparticles concentrations, the fluorescenceenhancement efficiency had a maximum.(4) P(St-co-AA) microspheres were prepared by Soap-free EmulsionPhotocopolymerization of St and acrylic acid (AA) in water using2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone. The structure of microspheres werecharacterized by FTIR, The shape of microspheres were characterized TEM,The size and sizedistribution of microspheres were characterized by LLS, The sizes of microspheres werearound70nm, Conversion rate of photopolymerization is up to86%.