Date of Award


Publication Type

Master Thesis

Degree Name



Mechanical, Automotive, and Materials Engineering

First Advisor

Derek D. N. Northwood

Second Advisor

Reza R. R. Riahi




Electrospinning is a method centered on electrostatic forces for fabricating continuous nanofibers with a substantial active surface area per mass unit. One of the essential parameters that affect a polymer's ability to create nanofibers is the chain length, given by the molecular weight. In this study, polyethylene oxide (PEO) with molecular weights from 100,000 to 5,000,000 g/mol were used to investigate the effect of molecular weight on the shape, size, and morphology of the fabricated fibers. The electrospinning experiments were conducted at flow rates ranging from 4.16 to 16.67μL/min and working distances between 10 and 20 cm. The collected fibers were analyzed using Scanning Electron Microscopy (SEM). Based on the solution and processing conditions, different structures from droplets, and heavily beaded fibers to defect-free mats were obtained. PEO's water-based solutions produced bead free fibers for molecular weights in the range of 100,000 to 900,000 g/mol for a range of processing conditions. However, the processing window for the formation of bead free fibers was more restricted for water-ethanol solutions than for deionized water solutions. Furthermore, the electrospun jet of ultra-high molecular weight PEO (5,000,000 g/mol) solutions showed very small bending instabilities, which reduced the chance of drying the jet during its flight time, even with a relatively high working distance (20cm). Therefore, the products exhibited over-wetting and film formation. The results are discussed in terms of the viscosity and entanglement number, (ne) soln, of the PEO solution.