Preparation Of Organic/Inorganic Hybrid Composites From ATRP Or RAFT

With the development of nanotechnology, organic/inorganic nanocomposite particles have been of great interest based on the fact that the inorganic maintains intrinsic predominant optical, electrical, and magnetic properties while the organic enahnces mechanistic capability and biocompatibility. More recently, the synthesis of organic/inorganic hybrid nanoparticles with stimuli-responsive, antibacterial, and biocompatible properties has attracted special interest. Living radical polymerization, especially atom transfer radical polymerization(ATRP) and reversible addition fragmentation chain transfer (RAFT) radical polymerization, has become a main method for preparation of these kinds of nanoparticles just because of its merits to control the structure and the surface properties of polymeric materials. In this dissertation, several different organic/inorganic nanocomposites including the poly(methyl methacrylate)(PMMA)-grafted silica nanoparticles, a novel polyelectrolyte-grafted core-shell organic/inorganic hybrid nanospheres which possesses a hard backbone of silica nanoparticles and a soft shell of cross-linked poly(ionic liquids) (PILs), hollow polyelectrolyte nanospheres and a poly(ionic liquid)brush surface modified silicon wafer with tunable wettability, reversible switching between hydrophilicity and hydrophobicity, have been successfully synthesized.A novel functional ion liquid [1-(4-vinylbenzyl)-3-butyl imidazolium hexa- fluorophosphate(PVBIm-PF6) has been synthesized successufully. And using it as a monomer, with 2-bromoisobutyryl bromide and 3-aminopropyltriethoxysilane as the initiator, butyronitrile as the solvent, CuBr as the catalyst and PMDETA as the ligand, well-defined poly [1-(4-vinylbenzyl)-3-butyl imidazolium hexafluoro- phosphate brushes with tunable wettability using surface initiated atom transfer radical polymerization (ATRP) are synthesized. Kinetic studies revealed a linear increase in polymer film thickness with reaction time, indicating that chain growth from the surface was a controlled process with a'living'characteristic. Furthermore, the surface of poly (ionic liquid) brushes with tunable wettability, reversible switching between hydrophilicity and hydrophobicity can be easily achieved by exchanging their counteranions.Methyl methacrylate is polymerized by using functional silica with peroxide groups as the initiator, 2-cyanoprop-2-yl dithiobenzoate as the RAFT agent and toluene as the solvent, through a reversible addition fragmentation chain transfer (RAFT) radical polymerization at 80℃. Polymerization using this treated silica initiator displayed the diagnostic criteria for a'living'/controlled radical polymerization. The molecular weight of the grafted polymer and the thickness of the polymer film can be controlled and linearly increase with the conversion of monomer.The kinetic studies show that ln([M]0/[M]) increases linearly with the increase of polymerization time. The surface topography analysis of these particles is carried out through TEM and AFM.Using PVBIm-PF6 as a monomer, initiator immobilized silica nanoparticles an initiator, CuBr as the catalyst, PMDETA as the ligand, and propionitrile as the solvent, a new core-shell hybrid nanosphere, with silica nanoparticles as core and crosslinked PVBIm-PF6 and PDVB as shell is prepared via surface-initiated ATRP polymerization. After removal of the silica core, nearly monodispersed hollow polyelectrolyte nanospheres are obtained. TEM result indicates that the average particle size of the hollow nanospheres to be around 250 nm, and the average diameter of the hollow core was ca. 200 nm with a shell thickness of ca. 25 nm. The obtained hollow polyelectrolyte nanospheres could be applied in release-control systems, the related researches are going under way.