Thermal Properties of Electrospun Fibers, with Research Opportunities for Deaf and Hard of Hearing Interns

Tufts University, Medford MA

Investigators

Abstract

NON-TECHNICAL SUMMARY: Polymer fibers are used in a wide variety of applications such as textiles. Now, through a process called electrospinning, it has become possible to make polymer fibers with extremely small diameters, much smaller than a human hair. Ability to create very small fibers is significant because it opens up the possibility for use in more advanced applications, for example as oil-water separation membranes for provision of clean water (promoting human welfare), or as supports to assist the growth of human cells like neurons (promoting human health). The first part of the research project involves making small diameter polymer fibers and characterizing their properties. The next part involves heating these small diameter fibers to discover what changes will occur in the structure of the fibers when they experience heating. For example, some fibers when they are heated may shrink, twist up, melt, or completely fall apart, depending upon how much heat they experience, and how fast they are heated up. There are also positive changes that may occur in the fibers, such as becoming stronger and less likely to break, or developing more resistance to chemicals which could attack them. Making small diameter fibers and studying these properties will provide important fundamental information to optimize their structure and behavior for use in their intended applications. The proposed research also will provide education and training to graduate and undergraduate students. Societal benefit will be derived from the internship program for deaf and hard of hearing students. This program will contribute to improving the diversity of the scientific workforce, by increasing the participation in science and technology of persons with disabilities, who belong to a group under-represented in these fields. TECHNICAL SUMMARY: Advanced methods of thermal analysis, such as temperature modulated and fast scanning chip calorimetry, will be used for fundamental studies of electrospun micron to nanoscale fibers. These approaches will be used to study crystallization, and the glass and liquid states, of fibers and droplets made from melting the fibers. Candidate polymers will have glass transition temperatures above room temperature. Examples include nylon 11, poly(ethylene terephthalate), poly(butylene terephthalate), or, poly(vinyl alcohol), which degrades at its melting temperature. The technical objectives are to: 1. prepare an array of electrospun fibers, and investigate thermal properties in relationship to fiber morphology and structure; 2. use fast scanning chip calorimetry on fibers, including polymers that degrade above their glass transition temperatures, to minimize effects of degradation on thermal properties; and, 3. measure nucleation and growth processes in droplets made from these fibers, and compare with behavior in bulk materials. The amounts of crystal, mobile amorphous, and rigid amorphous phases will be evaluated from the heat capacity increment at the glass transition. By using the fast scanning approach, the process of nucleation and crystal growth will be evaluated over six orders of magnitude in the cooling rate. The thermal analysis undertaken will provide new experimental protocols and aid in the evaluation of fast scanning data from semicrystalline polymers. The research will increase the participation in STEM fields of under-represented groups, especially persons with disabilities, through the summer program for deaf and hard of hearing undergraduate interns. Through collaborative projects, fibers for more applied uses will be studied, such as fibers for oil-water separation, or oriented fibers for guided growth of neurons.