Implication of stable jet length in electrospinning for collecting well-aligned ultrafine PLLA fibers

Stable jet based electrospinning (SJES) has recently emerged as a straight-forward approach for the continuous fabrication of well-aligned ultrafine fibers and fiber assemblies. This article reports on the influences of some pivotal solution parameters including solvent, polymer molecular weight, and concentration on the formation of a stable jet length (SJL) in electrospinning of a biodegradable polymer, poly(l-lactide acid) (PLLA). Our results reveal that enhanced critical SJL can be achieved at lower solvent dielectric constant and higher viscoelasticity of solutions contributed by the molecular weight and concentration, beneficial for achieving higher degree of fiber alignment. Moreover, hierarchical orderliness including the macroscopic fiber alignment, the elongation along the fiber direction of microscopic pores on the fiber surface and the molecular orientation within the electrospun PLLA fibers, can be modulated by the SJL. The molecular orientation and crystallinity of the aligned PLLA fibers from SJES increased with increasing the SJLs. Also, the measured tensile properties data suggest a positive trend associated with the SJL. This study thus allows establishing a solid correlation of SJL with respect to the macroscopic alignment, internal molecular structural development, and mechanical performance of the electrospun ultrafine PLLA fibers pertaining to the SJES.