Preparation Of Organic/Inorganic Hybrid Composites Via Surface-Initiated Nitroxide-Mediated Radical Polymerization

As nanoscopic science, technology, and engineering have been rapidly developed in recent years, nanomaterials have attracted widespread attention for their specific capability in the optics, electrics, calorifics, magnetics, catalysis and mechanics because of their high activity, good selectivity, tremendous specific surface and small size. Polymer films with thicknesses in molecular dimensions attached to solid substrates are expected to have a wide application. Recently, surface-initiated polymerization (SIP) was successfully applied in modifying inorganic surfaces with polymers.In this thesis, the recent development of surface-initiated polymerization (SIP) is reviewed. The theory,experimental approaches and research prospects of the surface-initiated polymerization are introduced extensively. The applications of this technique such as the patterned nanostructures of polymer films and polymer brushes are also discussed in detail. Surface-initiated nitroxide-mediated radical polymerization has been studied and some structurally well-defined polymer brushes have been prepared. With those functional thin films we could modify the inorganic particles and improve effectively the surface properties. The main contents are lists in the following:(1) Polymer-grafted nanosilica hybrid composites which possess a hard backbone of nanosilica and a soft shell of brush-like polystyrene (PSt) and poly (styrene-co-maleic anhydride) (PSMA) were prepared via"grafting through"strategy based on nitroxide-mediated radical polymerization (NMRP) using 2, 2, 6, 6-tetramethylpiperidine-N-oxyl (TEMPO) as mediator. Finally, well controlled molecular weight (Mn) and narrow molecular weight distributions (Mw/Mn) of polymer chains were grown from the surface of nanosilica.(2) Polymer-grafted montmorillonite (MMT) hybrid composites were prepared via"grafting from"strategy based on NMRP using TEMPO as mediator. PSt chains with controlled molecular weights and polydispersities were grown from the alkoxyamine functionalized MMT surface. The TG results show that a proportional relationship was obtained between the polymer grafting and the polymerization times. As assessed by GPC analysis,the molecular weight of the grafted polymer increase linearly with the increase of conversion·The linear relationship between ln([M]0/[M]) and time can be observed. (3) The polymer/palygorskite (PT) composites have been prepared via surface-initiated nitroxide-mediated radical polymerization. A novel water-soluble quaternary ammonium alkoxyamine was first synthesized and attached to the PT surface by cation exchange. The observed narrow molecular weight distributions (Mw/Mn), linear kinetic plots and linear plots of molecular weight (Mn) versus conversion for the free polymer formed in solution indicate that the chain growth from the PT surface is a controlled process with a"living"characteristic.