Micro- and nano-fibrous structures: Fabrication and application

This dissertation explores the fabrication of micro- and nano-fibrous structures by electrospinning. The simplicity of the process, the diversity of electrospinnable materials, and the unique features associated with electrospun fibrous structures make electrospinning and resultant micro- and nano-fibers attractive for a broad range of applications, including enzyme immobilization, reinforcing materials, and nanostructured ceramics, which were systematically discussed in the work.;Chapter 5 and 6 cover the preparation of the cellulose nanocrystal (CNC)-based nanocomposites. In chapter 5, CNC with rodlike, spherical, and network-structured morphologies were prepared by sulfuric acid hydrolysis and freeze-drying. The as-prepared CNC showed quick aqueous dispersion capability, high thermal conductivity, large specific surface area, and mesoporous structure. Electrospinning has been proven to be an effective method to incorporate CNC into polymeric nanofibers in chapter 6. Crosslinking of poly(acrylic acid) (PAA)/CNC nanocomposites was accomplished by heat treatment with CNC acting as a crosslinking agent. The PAA/CNC nanocomposites exhibited excellent water resistance, high thermal conductivity, low weight loss upon heating, and superior mechanical properties.;Chapter 7 and 8 address the fabrication of nanostructured ceramics by electrospinning. In chapter 7, noncovalent functionalization approach was employed to disperse carbon nanotubes (CNTs) into alumina nanoparticle suspensions. Alumina/CNT composite particles were transformed to continuous composite fibers via electrospinning followed by high temperature calcination. The axial alignment of CNTs observed in the composite fibers is promising for developing textured ceramics. In chapter 8, nanoporous silicon oxycarbide fibers (SiCO) with luffa-like shells were successfully prepared. The shell-core structures with patterned ridges on the shell and nanoparticles in the core showed superhydrophobicity and demonstrated an exceptional ability to absorb oils and organic solvents up to 39-fold of the material mass.;Chapter 1 gives a general review of the history and process of electrospinning technique and some interesting applications of the electrospun fibers. Chapter 2 reports the fabrication and crosslinking of non-ionic polyacrylamide (PAAm) fibers. The successfully crosslinked PAAm hydrogel nanofibrous membrane was used for entrapping beta-galactosidase. In chapter 3, Cibacron Blue F3GA (CB) bound cellulose (Cell) nanofibrous membranes (CB-Cell) were prepared and studied as affinity membranes for lipase. In chapter 4, multilayer coatings of lipase and CB onto Cell nanofiber surface was realized by the layer-by-layer (LBL) technique.