Studies Of ATRP In Aqueous Media And Preparation Of Several Functional Hybrid Materials

Recently, there are four kinds of methods arising in the fields of livingradical polymerization: they are initiator-transfer agent-terminator (Iniferter),nitroxide mediated polymerization (NMP), reversible addition and fragmentationchain transfer polymerization (RAFT) and atom transfer radical polymerization(ATRP). ATRP is an entirely new living radical polymerization method since1995. It has many advantages including in the formation of the lowpolydispersities, predetermined molecular weights and well-defined structurepolymer over other living polymerization methods. Furthermore, ATRP can alsobe used in the field of surface-initiated polymerizations and polymer brushes canbe easily grown from the initiator modified substrates. So many functional hybridmaterials can be synthesized by ATRP method.As an environmental friend media, water has received more and moreattention. With the development of studies of ATRP, researchers found out thatthe polymerization process still exhibit living characters by using water as thereaction media. Later, researchers found that water not only acted as thepolymerization solution, it can also help to accelerate the polymerization process.Moreover, it can make the polymerization proceed at ambient temperature andmuch time was saved during the polymerization process. So the studies of ATRPin aqueous media attracted much interesting of the researchers. On the other hand,direct and reverse ATRP have been carried out successfully in emulsion.In chapter 2, immobilization of α-bromoester initiator on spherical silicongel for the subsequent ATRP was first carried out. Then surface-initiated ATRP ofmethyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), methylmethacrylate (GMA) and N-isopropylacrylamide (NIPAM) were carried outseparately on the above with initiator modified silicon gel in aqueous media atambient temperature. The resulting hybrid particles owned core-shell structureand the polymer content in them was very high (>30%). In this process ofsurface-initiated ATRP, water acted as a promoter rather than merely as a solvent.Both the low PDI and the subsequent growth of MMA from the PMMA modifiedsurface exhibited living characters. Then two kinds of metal ions (Cu2+ and Cd2+)were introduced into the PHEMA chains grown from the silicon gel particles bythe comlexing bond between the hydroxyl groups and metal ions. As a result,these two kinds of polymer metal complexes (PMCs) modified silicon gel withmore thermal stability and excellent paramagnetic property were obtained. In theend, a relatively high concentration of glucose oxidase (GOx) was coupleddirectly to the well-defined PGMA brushes via the ring-opening reaction of theepoxide groups with the amine moieties of the enzyme.In chapter 3, the initiator for ATRP modified SiO2 nanospheres were firstsynthesized. Then surface-initiated ATRP HEMA, GMA and NIPAM werecarried out separately on the above with initiator modified SiO2 nanospheres inaqueous media at ambient temperature. The resulting hybrid particles owedobvious core-shell structures and the polymer shell can tune the properties ofSiO2 nanospheres' surface. For example, the PNIPAM/ SiO2 nanospheres hybridparticles showed good thermoresponsiveness because PNIPAM is a kind ofthermoresponsive polymer. Then by using the hydroxyl groups in PHEMAbrushes as the ligand, Cr3+ was introduced into PHEMA brushes and a new kindof PMCs modified SiO2 nanospheres was obtained. It can be used as a catalyst inthe CO2-dehydrogenation of ethane and it showed good catalytic properties. Inthe end, GOx was immobilized on the well-defined PGMA brushes grown fromSiO2 nanospheres via the same reaction as the method in chapter 2.In chapter 4, thick PHEMA brushes (>350nm) on α-bromoester initiatormodified flat silicon wafers were obtained by water-accelerated surface-initiatedATRP first and the polymerization process showed good living characters. Thenby using the hydroxyl groups in PHEMA brushes as the ligands, Cu2+ wasintroduced by the complexing bond and PMCs were formed. In the end, we usedNaBH4 to reduce Cu2+ in PMCs and nanoparticles of Cu0 were formed mainly onthe surface of the PHEMA brushes. Furthermore, PMMA brushes, PNIPAMbrushes and PMMA-PNIPAM block copolymer brushes were also grown fromthe above α-bromoester initiator modified flat silicon wafers and the PNIPAMbrushes modified silicon wafer exhibited a little thermoresponsibility.In chapter 5, Reverse ATRP of styrene in emulsion was thoroughly studiedand it carried out successfully by using the initiate-catalyze system made up ofAIBN, CuCl2, phen or bpy. The polymerization process showed living characters:molecular weight and monomer conversion were in a linear relationship;themolecular weight distribution (Mw/Mn) remained fairly low. The latex was verystable and the size of it was mean when using Brij-98 as the surfactant. Thenunder similar polymerization conditions, reverse ATRP of MMA was also carriedout in emulsion. This kind of initiate-catalyze system must be widely used inapplication because it has many advantages such as simple, cheap and so on. Inthe end, by using bromide substitute polystyrene as the grafting initiator, ATRP ofMMA was carried out in emulsion. The grafting copolymerization processexhibited some living characters and it opened a new way to synthesize graftingcopolymers in emulsion.