Preparation Of 1D, 2D, 3D Nanoparticles/Polymer Composite Nanomaterials Based On Metal Methacrylate Monomers

Semiconductor nanoparticles have been a subject of intensive research due totheir optical, electrical, magnetic, catalytic properties, and promising applications inoptical materials, sensors, solaode and so on. However, it is difficult to utilize thesenanoparticles directly because of their small size, large specific surface area andhigh surface energy. Making these nanoparticles to real-world application, it isrequired to stabilize them in inert matrices. Polymer serves as good host materialsfor functional nanoparticles. By incorporation of optic, electrical, and magneticsemiconductor nanoparticles into polymer matrices, multifunctionalized compositematerials can be synthesized. Much attention has been paid to the semiconductornanoparticles/polymer composite materials in recent years.In this thesis, we prepare a series of one dimensional (1D), two dimensional(2D) and three dimensional (3D) semiconductor nanoparticles/polymernanocomposite materials based on metal(Ⅱ) methacrylate monomers. Since thereare two C=C bonds in each metal(Ⅱ) methacrylate molecule, cross-linked structuresare produced in the polymerization procedure, which not only enhance themechanical strength and the thermal and chemical stability of the compositematerials, but also favor formation of uniform semiconductor nanoparticles in theentire polymer matrix in the process of sulfuration. Therefore, metal(Ⅱ)methacrylate molecules are ideal monomers to prepare semiconductornanoparticles/polymer composite materials.In chapter 2, we describe the fabrication of SiO2@PCDMA core-shellnanospheres through the atom transfer radical polymerization (ATRP) of cadmiumdimethacrylate (CDMA) on silica nanospheres. We find that it was convenient andreproducible to control the thickness of poly(cadmium dimethacrylate) (PCDMA)shells by adjusting the concentration of Cu+ ions catalyst. CdS nanoparticles are thengenerated in-situ in the PCDMA shells by a gas/solid reaction, and CdSnanoparticles/polymer composite shells are formed. The CdS nanoparticles withdiameters of approximate 3 nm are attributed to hexagonal system (a = 4.121 ?, c =6.682 ?). The intense emission of CdS nanoparticles occur centered at 617 nm (λex =453 nm). Furthermore, we also successfully prepare block copolymer shellsconsisting of PCDMA and PMMA on silica nanospheres by repeatedly performingthe surface-initiated ATRP procedures using CDMA and MMA as the monomersrespectively. SiO2@polymer-CdS@PMMA and SiO2@PMMA@polymer-CdScore-shell nanospheres are fabricated.In chapter 3, lead dimethacrylate (Pb(MA)2) crystals with lamellar structuresare prepared. The distance between each two adjacent layers is about 1.2 nm, and thePb(MA)2 molecules pack in form of hexagon in one layer. Since there areunsaturated bonds and metal ions in the Pb(MA)2 molecules, we convert thesemonomeric lamellas into PbS nanoparticles/polymer composite lamellar structuresthrough the combined use of γ-ray irradiation and a gas/solid reaction. In thisapproach, γ-ray irradiation offers an ideal means to fabricate polymer lamellarwithout changing the morphology and introducing any other reagent. After exposingthe poly(lead dimethacrylate) (P-Pb(MA)2) lamellas to H2S gas, PbS nanoparticlesare generated in-situ. The PbS nanoparticles with diameters of 4 nm are welldispersed in the polymer lamellas and have a cubic fcc structure (a = 5.936 ?).In chapter 4, we report for the first time on the preparation of organicmetal-salt (Pb(MA)2) nanowires through a dissolution-recrystallization process. Thenanowires with diameters of 200~300 nm, and lengths ranging from tens tohundreds micrometers, have excellent thermal stability and solvent resistance. Wealso have discussed the mechanism for the formation of these nanostructures in thischapter. Furthermore, we convert these monomeric nanowires into PbSnanoparticles/polymer composite nanowires without altering their morphology,through the combined use of γ-irradiation and gas/solid. γ-Ray irradiation offers anideal means to fabricate polymer nanowires without changing the morphology andintroducing any other reagent. The obtained polymer nanowires also have excellentthermal stability and solvent resistance as are the Pb(MA)2 nanowires. It has beenproved in our experiments that, the irradiation process is necessary to stable thewirelike morphology. PbS nanoparticles are prepared in-situ by exposing theP-Pb(MA)2 nanowires to H2S gas at room temperature. The dense PbS nanoparticleswith diameters of approximate 4 nm are separated from each other and welldispersed in the polymer nanowires. The PbS nanoparticles have a cubic fccrock-salt structure (a = 5.936 ?). Moreover, we also prepare a novel fluorescentorganic metal-salt (Eu(MA)3) nanowires through this dissolution-recrystallizationprocess.In summary, we have developed the methods for preparing 1D PbSnanoparticles/polymer composite nanowires and 2D PbS nanoparticles/polymercomposite lamellar structures based on Pb(MA)2 molecules. Furthermore, we alsoprepared 3D silica/CdS nanoparticles-block copolymer core/shell nanospheres basedon CDMA monomers.