Electrospun Polymer Nanocomposite Fibers And Their Applications

Electrospinning is a facile and versatile method for preparing continuous polymericand composite fibers with diameters ranging from a few nanometers to severalmicrometers. Electrospinning technique uses an electrical field to draw very fine（typically on the micro or nano scale） fibers from a polymer solution or moltenpolymer. The process of electrospining does not require the use of coagulationchemistry or high temperatures to produce solid threads from solution， which makesthe process particularly suited to the production of fibers using large and complexmolecules. Due to these advantages, the electrospun fibers have been widely used inmany areas, such as such as catalysis, filtration, absorption, sensor, drug deliverysystem, etc.In chapter1, we first give an introduction of the electrospinning technique in terms ofits historical, current, and future research tendency as well as its practical applications.We also introduce the basic principle of the electrospinning process theoretically, byanalyzing the generation of the capillary jet flow, the stretch of the jet, and theinstability of the jet. We also discussed the effect of the precursor material,concentration, and the external environment on the morphology of the electrospunfibers. At last, we also summarized the applications of the electrospun fibers andestablished the research focus of this thesis.In chapter2, we studied the electrospining of polystyrene andpolystyrene/polyethylene glycol blend, and prepared electrospun polystyrene andpolystyrene/polyethylene glycol composite fibers.The effects of the solution concentration of PS and the addition of PEG into the PS solution on fiber morphologywere discussed. By adjusting the concentration of PS solution, different morphologiesof PS from beads to beads-on-fibers, and fibers were obtained. By using opticalmicroscopy, it was found that PS with a concentration of25wt%could lead to fiberswith well-defined morphology. Furthermore, polyethylene glycol was then added tothe PS solution with the optimized concentration of25wt%, and electrospinning ofPS/PEG blend was conducted.By using polarized microscope observation, it wasfound that core-shell structured PS-PEG fibers were obtained after theelectrospinning.In chapter3, we have synthesized the block copolymer of PEG-b-PS by using ATRPmethod. The as-synthesized the PEG-b-PS block copolymer was characterized by theFTIR,1H-NMR and GPC. Furthermore, by using this PEG-b-PS block copolymer asa solubilizing agent added to PS/PEG blend, homogeneous electrospun fibers withoutphase separation were obtained.In chapter4, catalytic nanofibers are prepared by the immobilization of Aunanoparticles （AuNPs） onto the surface of cross-linked electrospun poly（4-vinylpyridine）（P4VP） nanofibers.The crosslinking of the P4VP nanofibers by1,4-diiodobutane via quaternizationreaction greatly enhances the stability of thenanofibers against the solventdissolution, which can be then used as promisingplatform for the immobilization ofcatalytic metal nanoparticles. The AuNPsimmobilized cross-linked P4VP nanofibershas shown a good catalytic activity for thereduction of4-nitrophenol （4-NP） to4-aminophenol （4-AP）.