Electrospinning is a convenient and versatile method to fabricate different kinds of one-dimensional nanostructures such as nanofibers, nanotubes, and nanobelts from a wide array of polymers. Fundamental studies on various aspects of the electrospinning process have identified important parameters that affect the fiber size and morphology. The molecular weight is the predominant factor that determines the diameter of the collected fibers. The relationship between polymer molecular weight and the types of structures produced by electrospinning technique has been widely investigated. As early as 1971, Baumgarten reported the effect of the polymer concentration and viscosity on electrospinning processes. When the polymer concentration improved from 7% to 20%, the viscosity increased from 0.17 Pa·s to 21.5 Pa·s correspondingly, and the diameter of the fiber increased with increasing solution concentration. Electrospinning solution generally consists of a polymer and a solvent, which belongs to the binary system and is different from the one-component fluid.