Light Scattering of Electrospinning Jet with Internal Structures by Flow-Induced Phase Separation

Area of Science:

• Materials Science
• Polymer Science
• Fluid Dynamics

Background:

• Electrospinning is a widely used technique for producing polymer nanofibers.
• Understanding the internal dynamics of the electrospinning jet is crucial for controlling fiber morphology.
• Phase separation phenomena can significantly influence the structure formation during electrospinning.

Purpose of the Study:

• To provide direct morphological evidence of extension-induced phase separation in electrospinning jets.
• To investigate the formation of internal structures within the jet using advanced imaging and scattering techniques.
• To correlate jet extension rates with phase separation and self-assembly processes.

Main Methods:

• High-speed video imaging of the electrospinning jet.
• Light scattering techniques (Vv and Hv configurations) to analyze internal structures.
• Rheological measurements to determine polymer relaxation rates.
• Development of a light scattering model for quantitative analysis.

Main Results:

• Observed two types of internal structures: long strings and short ellipsoids within the PVA/water electrospinning jet.
• Demonstrated that internal structures dominate light scattering, masking the jet's contribution.
• Quantified high extension rates (approx. 3420 s⁻¹) near the Taylor cone apex, exceeding polymer relaxation rates.
• Observed chain anisotropy parallel to the jet axis via Hv scattering.

Conclusions:

• Extension-induced phase separation occurs in the Taylor cone apex for PVA solutions.
• This phase separation triggers self-assembly, forming strings and bulges in the jet.
• These structures evolve into nanofibers upon solvent removal.