Using the electrospinning (ES) technique for processing nano-scale fibers, the effect of confinement on fundamental physical and structural properties will be investigated. Confinement refers to restrictions on the mobility of the polymer chains brought about by addition of fixed barriers inside the fibers. Besides the crystals of the polymer, additives such as carbon nanotubes, organically modified silicates, or silica, lead to formation of nanocomposites in which these nanofillers also serve as fixed barriers leading to chain confinement. The relaxation properties of the nanocomposite are altered, leading to beneficial improvement of properties, for example an increase in the use temperature, and an increase in the mechanical modulus. The phase structure and physical properties of ES polymer-based nanocomposites will be studied as they relate to the fiber orientation, degree of crystallinity, filler type, and amount. The objectives are to: 1. Provide fundamental understanding about the relationship between crystals or nanofillers and the non-crystalline portions of the semicrystalline electrospun nanocomposite fibers, especially through new methods of quasi-isothermal heat capacity analysis and fast scanning chip calorimetry; 2. Correlate the fiber properties (e.g., diameter, crystallinity, chain orientation, filler type, amount, and dispersion) to the degree of constraint; and 3. Separate the confining effects of the filler from those of the crystals. Techniques to be used in the work include high precision, high accuracy heat capacity measurements by temperature modulated differential scanning calorimetry to quantify the level of confinement. For the first time, the techniques of fast scanning chip calorimetry on ES fibers (through international collaboration with the Schick group in Rostock, Germany) will be applied to study homogeneous nucleation in ES fibers. Also for the first time, dielectric relaxation spectroscopy (DRS) will be used to characterize the dipolar relaxations of ES fibers. These studies will provide a knowledge base which will enhance the use of ES fiber materials in technologically important areas such as non-woven textiles, regenerative medicine, and transport and catalysis.
NON-TECHNICAL SUMMARY:
Non-woven membranes will be created using very small diameter fibers, on the nano-scale, by applying a high electric field to a solution containing polymer and additives (such as carbon nanotubes or clay). Nanofibers formed this way are stronger and more heat resistant compared to conventional large diameter fibers. The processing conditions and nature of the additive will be varied to see which combinations yield nanofibers with the best properties. These non-woven fabrics are candidate materials for use as filtration membranes, in catalysis, for drug delivery, and as a component of smart clothing materials. Both national and international collaborations have been established for conducting this research using specialty equipment and novel processing conditions. To provide research opportunities for students with disabilities, four deaf and hard of hearing undergraduate students will participate in an internship, and perform research on the project during the summer months. These interns will learn to make the non-woven nanofibers, heat treat them, and study their physical properties.
