Location

MoSE Room 3201A

Shiqi Wei

Advisor: Dr. Blair K. Brettmann

 

will propose a doctoral thesis entitled,


Electrospinning the “unelectrospinnable”: Using molecular interactions within polymer solutions to improve the electrospinning process


On


Monday, December 2 at 10:00 a.m.
MoSE Room 3201A

and/or

 Virtually via MS Teams

 

 

Committee:

  • Dr. Blair K. Brettmann, Advisor, ChBE and MSE
  • Prof. Edward Botchwey, BME
  • Dr. Scott Danielsen, MSE
  • Prof. Seung Soon Jang, MSE
  • Prof. Younan Xia, BME

 

 

Abstract

Electrospinning is a versatile processing technique for producing fiber mats with fibers of submicron-scale diameter. Successful electrospinning of polymer solutions to form fibers relies on polymer chain entanglements to maintain jet integrity against the Rayleigh instability during electrospinning, resulting in fibers. However, when polymer entanglements are insufficient (with low polymer molecular weight or low polymer concentration), carrier polymers, cosolvents, and additives are used to adjust the viscoelasticity and physical properties of the polymer solution. Herein, I propose to investigate the approach of using additives or cosolvents to enhance intermolecular interactions, thereby expanding the electrospinning processing window and enabling the electrospinning of a high-performance ultrafine fibrous hydrogel.

This proposal outlines the investigation of the intermolecular interactions within polymer solutions and their effects on the electrospinning process and product performance. Viscosity, a critical physical parameter of polymer solutions for electrospinning, is influenced by polymer entanglements and other interactions within the polymer solution. In my thesis project, I will study electrospinning of polymers without sufficient entanglements (such as solutions with low polymer concentration or low polymer molecular weight) by introducing polymer-additive interactions (Aim 1) or polymer-cosolvent interactions (Aim 2).  I will also research the effect of polymer solution properties on the performance of the product of ultrafine fibrous hydrogel (Aim 3). Specifically, Aim 1 investigates the impact of additive valency on the critical electrospinning polymer concentration of polyvinyl alcohol (PVA) in aqueous conditions. Additives with three or eight amine groups from melamine or OAP-POSS, respectively, will be used to probe the effect of valency on the improvement of electrospinnability. In Aim 2, the mechanism of the positive effect from adding 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) to poly(L, lactic acid) (PLLA) in dichloromethane (DCM) system on electrospinnability will be studied. In Aim 3, models of ultrafine fibrous hydrogel will be established by chemically crosslinking the electrospun fibers with UV light and physically crosslinking the electrospun fibers with the freeze-thaw method. In Aim 3, I will utilize the conclusions from Aim 1 and Aim 2 to study how the solvent or additive affects the performance of ultrafine fibrous mats and, eventually, the performance of hydrogels made from the electrospun mats.

Structure, properties, processing, and performance are the four essential components in materials science and engineering. For each aim, I will study how interactions within polymer solutions, either from small molecule additives, cosolvent, or oligomers, change the polymer's molecular structure in the polymer solution. The change in molecular structure will alter the chemical or physical properties of the polymer solution, such as rheology, vapor pressure, and surface tension. The properties of the polymer solution will further affect the processability, which is characterized by the processing window of electrospinning for the polymer solution, such as the critical electrospinning concentration (lower limit of polymer concentration for electrospinning of fiber). After processing, the molecular structure and properties of the processed ultrafine fiber mat will further enhance the performance, such as mechanical properties (modulus, elongation at break) and drug release rate of the resulting ultrafine fibrous hydrogel.

This research aims to expand the operational window for electrospinning by better understanding the secondary interactions within polymer solutions to guide further applications, such as the preparation of well-defined ultrafine fibrous hydrogel.