Synthesis of polyacrylonitrile/titania co-axial nanofibers via electrospinning

Titania nanofibers having polymer core were successfully prepared via the combination of sol-gel and co-axial electrospinning techniques, using polyacrylonitrile (PAN) in dimethyl formamide (DMF) as core solution and titania sol derived from titanium(IV) isopropoxide (TTIP), DMF, acetic acid and poly vinyl pyrrolidone (PVP) as sheath solution. For the co-axial electrospinning technique in this research, the core solution and the sheath solution were supplied separately to a co-axial nozzle. The effects of the flow rate of both core solution and sheath solution, and the electric potential applied were investigated in this research. The diameter of the electrospun fiber is increased when the flow rate of the core solution is increased. The uniform fibers with an average diameter of 380 nm could be fabricated by applying the electric potential of 22 kV on the co-axial electrospinning system, while the flow rate of the core solution and the sheath solution were 1.2ml/h and 0.9 ml/h, respectively. The core-sheath structure of the electrospun fibers was confirmed by using transmission electron microscopy. The electrospun co-axial fibers were then subjected to the calcination process. The crystallization of titania and the removal of PVP were found to depend upon the calcination temperature of the electrospun fibers. The presence of PAN core, which can withstand higher temperature than PVP, can provide flexibility to the final titania nanofibers. It is found that the biphasic titania nanofibers products with an average diameter of 150 nm can be obtained after calcination at 450 °C.