Electrospinning droplet formation

The surface tension seems more likely to be a function of solvent compositions, but is negligibly dependent on the solution concentration. Different solvents may contribute different surface tensions. However, not necessarily a lower surface tension of a solvent will always be more suitable for electrospinning. Generally, surface tension determines the upper and lower boundaries of electrospinning window if all other variables are held constant. The formation of droplets, bead and fibers can be driven by the surface tension of solution and lower surface tension of the spinning solution helps electrospinning to occur at lower electric field [57],... 

Electrospinning techniques are used to form particles and fibers as small as one nanometer in a principal direction. The phenomenon of electrospray involves the formation of a droplet of polymer melt at an end of a needle, the electric charging of that droplet, and an expulsion of parts of the droplet because of the repulsive electric force due to the electric charges. In electrospraying, a solvent present in the parts of the droplet evaporates and small particles are formed but not fibers. The electrospinning technique is similar to the electrospray technique. However, in electrospinning and during the expulsion, fibers are formed from the liquid as the parts are expelled (41). 

The electrostatic forces generated by the high electrostatic field can easily interact with electrically conductive liquids. In the case of classical electrospinning a droplet of solution is applied. If the interaction is adequate, the droplet forms a conical shape. This shape is called Taylor cone in honor of Taylor [59] who achieved significant results in the mathematical description of liquid surface formation. 

Figure 3.6 Top scheme Schematics of the formation of a linear supramolecular polymer from the self-organization of a heteroditopic monomer constituted by benzo-21-crown-7 and dialkylammonium salt. Bottom panels (a) SEM micrograph of a rod-like fiber, drawn from a chloroform solution, (b-d) SEM micrographs of nanofibers realized by electrospinning the linear supramolecular pol5nner. Spinning from acetonitrile solutions results instead in deposited droplets (e, 0- (g> h) TEM micrographs of the electrospun nanofibers. Adapted with permission from Ref. 78, Chem. Commun., 2011, 47, 7086-7088. Doi 10.1039/ clccll790d.

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