Preparation, Structure And Properties Of SF/PVA Blending Nanofibers With A Ternary Solvent

In this paper, silk fibroin (SF)/ polyvinyl alcohol (PVA) blending nanofibers were prepared via electrospinning in order to improve SF material's physical properties. The compatibility and spinnability of SF/PVA blending solution were investigated; fibers'morphology and structure were also characterized. The electrospun textiles possess many advantages such as small pore size, high surface area, very small diameters; these outstanding properties make the polymer nanfibers be optimal candidates for many important applications like biomedical science and scaffolding material for tissue engineering.The thesis contains following four main parts:1. The influence of solvent properties on the electrospinnability of SF was investigated using two different solvents, formic acid and mixing solvent of trifluoroacetic acid (TFA)/ dichloromethane (MC) (70/30 in weight). The regenerated SF solution obtained by dissolving the regenerated SF in these two solvents were transparent and did not aggregate or precipitate even though the solution was stored for a long time. The composition of solvents had effect on the surface morphology and diameter distribution of electrospun nanofibers. In the SF-formic acid solution, small beads and interconnected fibers were found, however using mixing solvents of TFA/MC, the fibers became more homogenous and smooth. Moreover, the spinning speed was faster. All attributed to solvent properties like boiling point, polarity, viscosity.2. With solvent mixtures of TFA, MC and water, SF/ PVA blending nanofibers mats were prepared using electrospinning method and influence of SF/PVA ratio on compatibility of the blend was investigated. Because of polarity of TFA, adding appropriate PVA in SF solution, the blending solution was more uniform and stable than water solution. But when the blending ratio was 80/20 and 75/25, the blending solution became turbid and precipitated due to aggregated and entangle PVA molecules themselves, resulting in worst spinnability.3. Nanofiber formation of SF/PVA by electrospinning was studied, the applied voltage and tip-to-collector distance were fixed. The results showed the flexibility of SF could be improved by adding PVA, the average diameter of the blending nanofibers was thinner than pure SF nanofibers due to higher conductivity of solution. Then Blending nanofiber mats were treated with organic alcohol in order to increase their stability and mechanical properties in the presence of water. After treatment, the fibers became tight, and the porous between fibers became smaller.4. The fiber morphology and structure were characterized with scanning electron microscopy(SEM), infrared(IR) and X-Ray diffraction. The results showed that there existed interaction between SF molecule and PVA molecule, the mechanical properties of the blending nanofibers were increased. After chemical treatment, it was indicated that the blending nanofiber mats had higher crystallinity and less solubility in water, the tensile strength and elongation were also improved.