In order for polymeric nanofibers to be used more widely, a thorough understanding of fiber-formation physics and fiber chemistry is critical. The research conducted using the Nanospider electrospinning apparatus will be transformational because it will provide answers to some fundamental questions involving polymer-solvent interaction, role of viscosity and surface tension in fiber spinnability, effect of potential gradient and collector distance (from needle containing the polymer). These answers are critical to provide innovative solutions to overcome technical barriers that exist in more widespread use of this technology. The Nanospider, in concert with other equipment already available at UMD, will propel UMass Dartmouth toward a niche area in material development and characterization that will attract local businesses and universities to assist their business/academic needs.
This award enabled University of Massachusetts Dartmouth (UMass Dartmouth) to acquire a Nanospider™ instrument for electrospinning submicron and micron-sized fibers. These fibers have promising applications in environmental treatment, tissue regeneration, drug delivery, and other areas. The PI and the co-PI were successful in generating submicron (average diameter = 554 nm; standard deviation = 200 nm) fibers of PolyAcryloNitrile (PAN) and micron-sized (average diameter = 1185 nm; standard deviation = 930 nm) fibers of PolyVinyl Alcohol (PVA). In both cases, interaction of process parameters (polymer molecular weight, the choice of the solvent, the weight% of polymer and solvent, relative humidity, air temperature, air flow rate and applied voltage) was thoroughly studied and optimal conditions were determined for continuous electrospinning. Electrospun PAN was hydrolyzed by alkaline hydrolysis to convert the nitrile group to form carboxylic acid group. The carboxylic acid group can function as a weak-acid cation exchanger. The advantages of a submicron electrospun fiber vis-à-vis other ion exchanger morphologies (e.g., resins, membranes, etc.) include the ability of the former to be used in decontamination of hazardous waste streams with a high percentage of suspended solids, and higher ion exchange capacity per unit mass. Ion exchange capacity of electrospun PAN fibers depends on the hydrolyzing alkali, temperature, hydrolysis time, and mixing conditions. We were successful in optimizing the afore-mentioned variables to generate a submicron fiber with an ion exchange capacity of 2.0 milliequivalent/gm. Fourier Transform Infra-Red Spectroscopy FTIR) and X-ray Photoelectron Spectroscopy (XPS) of electrospun fibers before and after hydrolysis confirmed that the nitrile bond was converted to carboxylate functional group. Three graduate and 2 undergraduate students have been trained in the use of Nanospider™. The graduate students are using the Nanospider™ to pursue research in the use of electrospun fibers in environmental treatment and tissue regeneration. The College of Engineering at UMass Dartmouth runs a Freshman Summer Institute (FSI) program where incoming freshman students spend a week during the summer at the campus and are engaged in many academic and extra-curricular activities. In 2012, FSI was held from August 6-10. As part of the project of one group (8 students), a trained graduate student demonstrated the capabilities of the Nanospider™ to the incoming freshmen. The PIs also discussed the process of electrospinning in a freshman "Introduction to Engineering" class and a senior-level technical elective in water and wastewater treatment, and demonstrated the use of the Nanospider™ to the class.
