ABSTRACT
All proposed explanations of the size- dependent behavior of electrospun polymer nanofibers based only on the effects of surface tension or near-surface layers cannot satisfactorily describe the aforementioned phenomenon quantitatively. McKenna and others argues that the surface tension contribution is insufficient to fully account for the observed overall rubbery stiffening behavior, which, actually, should be attributed to a mixture of both molecular stiffening and surface tension effects. Focusing on the confinement hypothesis, from the physical point of view, the confinement-induced size-dependent behavior of electrospun polymer nanofibers should be related to an internal scale parameter that is comparable with the scale of the system. Malkin and others have shown that high rate deformations of the macromolecular network results in the formation of large inhomogeneous structures: "grains" or "bundles". Taking into account the fact that the electrospinning process is accompanied by high strain rate, it is reasonable to assume that similar structures can be formed also in electrospun polymer nanofibers.
