Electrospinning is the most popular technique to prepare nanofibers for many polymer applications. The comparison of extension rates in the jet with the intrinsic relaxation rate of the fluid (both obtained from experimental measurements) is essential to understand the electrospinning for the general readers to appreciate the importance of molecular aspect of solution rheology in the electrospinning. 

Based on the light scattering experiments to obtain the jet diameter during electrospinning, we found that the extension rate (R) is position (or time) dependent; its magnitude is the highest at the apex (region I with a magnitude of R_I) and rapidly decreases to a relatively constant value in the main jet (region II with a magnitude of R_II) before reaching the jet end (region III), where the extension rate is zero. Our analyses of the extension rate in the straight jet reveal the general trend of R_I > R_II > t_d^-1, suggesting likely a sequential structure evolution leading eventually to the strings within the jet due to, first, the flow-induced large concentration fluctuations in single phase solution and, subsequently, phase separation eventually leading to evolution of the strings with increasing R, where t_d^-1 is the chain disentanglement rate.

We validated the flow-induced phase separation to disclose that the electrospun poly(vinyl alcohol) aqueous solutions evolve, in cascade, hierarchically self-organized dissipative structures along the electrospinning line. A brief discussion of flow-induced phase separation in the electrospinning jet will be given for the formation of nanofibers.