Surface Modification Of Natural Polymer Materials Via Surface-Initiated ATRP

In this thesis, surface modification of natural polymer materials via AGET ATRP (Atom Transfer Radical Polymerization with Activators Generated by Electron Transfer) or normal ATRP was demonstrated. The obtained materials composed of natural polymers and synthetic polymers have both advantages of natural polymers and synthetic polymers, which facilitates wider applications of the natural polymer materials.The work in this thesis can be summarized as follows:(1) Surface modification of chitosan nannospheres via iron-mediated AGET ATRP. Cross-linked chitosan nanospheres (SCTS) with an average diameter of 80 nm, were first prepared in a water/oil emulsion using glutaraldehyde as a crossing agent, and ATRP initiators were immobilized on the surfaces of the nanospheres. Iron(III)-mediated surface AGET ATRP was then successfully carried out on the SCTS using FeCl3·6H2O as the catalyst, PPh3 as the ligand, and ascorbic acid (VC) as the reducing agent in the presence of a limited amount air. The homopolymer, poly(methyl methacrylate) (PMMA), and amphiphilic block copolymer poly(methyl methacrylate)-b-poly(poly(ethylene glycol)methylether methacrylate) (PMMA-b- P(PEGMA)) were grafted onto the surfaces of the SCTS. Well-defined polymer chains were grown from the SCTS surfaces to yield individual nanospheres composed of a chitosan core and a well-defined, densely grafted outer PMMA or PMMA-b-P(PEGMA) layer. The kinetic of surface-initiated AGET ATRP of MMA in the presence of a limited amount of air was investigated. Linear kinetic plot and linear increase of molecular weight (Mn) with conversion for the sacrificial initiator initiated solution AGET ATRP, and linear plot of grafted percentage verse time were observed. The chemical composition of the nanosphere surfaces at different surface modification stages was validated by Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS).(2) Synthesis of filter paper with antibacterial activity via surface-initiated ATRP. Poly(tert-butyl acrylate) (PtBA) brushes were successfully grafted on the cellulose filter papers via surface-initiated ATRP. Then the grafting PtBA brushes were transferred into poly(acrylic acid) (PAA) in the presence of trifluoroactic acid (TFA), which can form chelate complexes with Ag+. The Ag+ was reduced in situ to obtain the silver nanoparticles modified cellulose filter papers. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA) and X-ray diffraction (XRD) were used to characterize the resulting products. The morphologies of the filter paper at different stages of surface modification were investigated by field emission scanning electron microscopy (FESEM). The silver nanoparticles modified filter paper performed good antibacterial ability against E. coli as compared with the original filter paper and PAA modified filter paper.