Preparation And Characterization Of Polymer Micro/Nano Particles Via Electrospray Ionization

Monodisperse colloids, especially polymer colloidal spheres with the diameter from nanometer to submicrometer have been attracting considerable attention for their potential applications in the field of optics, magnetics, electronics, colloidal chemistry, biochemistry and medicine. Polymers colloids of different chemical compositions can be produced as exceedingly uniform spheres by a process called emulsion polymerization. Recently, a large number of templating methods have been combined with the self-assembly of colloidal spheres. Thus these approaches are usually limited to the formation of colloidal spheres by using only some radical polymers, especially such as polystyrene (PS) and poly (methyl methacry-late) (PMMA) and not applicable for most of the other common polymers. In this paper, we use a simple method called electrospray ionization to obtain polymer microspheres. This method is applicable for most of common polymers such as poly (vinyl pyrrolidone) (PVP), polyacrylonitrile (PAN), polyvinyl alcohol (PVA) and or so. The ESI technique describes an experimental setup for the production of polymer colloid microsphere using an electrostatic force. There are basically three components to fulfill the process: A high voltage supplier, a capillary tube with a pipette or needle of small diameter, and a metal collecting screen. If the voltage surpasses a threshold value, electrostatic forces overcome the surface tension, and a fine charged jet is ejected. The jet moves towards a metal collecting screen actin as counter electrode. electrospray ionization (ESI) has found broad application in mass spectrometry (MS) as a nondestructive method for producing gas phase ions of biological and synthetic macromolecules. However, there is few report for further study of polymer colloid spheres by ESI though Morozov has prepared several polymer ions by ESI. My dissertation involves three parts: polymer pure microsphere, polymer compose microsphere containing of inorganic nanoparticles and carbon microsphere. On the first part of the dissertation, effect of concentrations, solvent, electric field and distance of tip-to-electrode to the morphology of polymer was further studied. The electrospraying PAN microspheres have been successfully prepared by using different concentrations of PAN electrospraying solutions. The morphology of microspheres was strongly affected by the parameters such as polymer concentration, applied voltage, and distance between the electrodes. In PAN/DMF solution, at above 6 wt%, the fibers formed due to high viscosity; At 2─4wt%, expected microsphers formed. The half hollow spheres were observed at 1wt%. Similarly, it can be observed at long distance or high applied voltage, too. Shape of the spheres is not influenced significantly by the species of solvent. At 3 wt% concentration, 10 cm from tip to collector, and 1.1 KV of applied voltage is the optimum condition for preparing microspheres. DSC and XRD results indicate that the PAN microspheres...