Research On The Surface-initiated Polymerization And Application

Atom transfer radical polymerization (ATRP) has been established as a powerful technique to prepare a variety of polymers with predetermined molecular weight, narrow molecular distribution, high functionality, and complex architecture. The commercialization of these new polymers will require detailed polymer reaction engineering investigation. The objective of this thesis has been to apply this technique to prepare well-defined functional polymeric materials such as bio-related materials and functional surfaces. Microemulsion polymerization is an effective method to prepare polymer/inorganic composite materials, which provides a large interfacial area and is generally less viscous. This thesis is composed of two main subjects: the synthesis of functional surfaces, such as antibacterial surface and thermo-responsive surface by surface-initiated ATRP; the preparation of the hydroxyapatite/poly (methyl methacrylate) composites in situ microemulsion polymerization.In the first part of this thesis, it is explored to prepare antibacterial surfaces and thermo-responsive surfaces. My work start with the preparation of functional polymer brushes of 4-vinylpyridine (4VP) via surface-initiated ATRP from polyimide (PI) films, followed by the alkylation of the grafted P4VP with hexyl bromide. The present surface functionalization method has the advantage of being effective in conferring polymeric materials with antibacterial properties. The antibacterial efficiency of the modified PI film is dependent on the amount of quaternary pyridinium groups on the surface. Moreover, Thermo-responsive surfaces are prepared from commercial poly (vinylidene fluoride) (PVDF) films via ATRP. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the N-isopropylacrylamide (NIPAAm) monomer. The temperature dependent swelling behavior of the surfaces in aqueous solution is studied by atomic force microscope (AFM). At 37°C [above the lower critical solution temperature (LCST, about 32°C) of NIPAAm], the seeded cells adhered and spread on the NIPAAm grafted PVDF surface. Below the LCST, the cells detached from the poly (N-isopropylacrylamide)-grafted PVDF surface spontaneously.In the second part of this thesis, we report the preparation of the HA/PMMA composites in situ microemulsion polymerization, in which HA microspheres are wrapped by PMMA. The thermal properties and sturctures of the composites are investigated by a differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FTIR spectroscopy, X-ray diffractometer (XRD), scanning electron microscopy (SEM). Compared with pure PMMA, the HA/PMMA composites show enhanced thermal properties. When the content of HA in the composites is 5 wt%, the glass-transition temperature of the composite increases from 114℃up to 132℃.