Electrospinning of Polyacrylonitrile Solutions at Elevated Temperatures

Abstract

Using a jacket-type heat exchanger to control the solution temperature, the electrospinning of polyacrylonitrile/dimethylformamide (PAN/DMF) solutions with various concentrations was carried out at temperatures ranging from ambient to 88.7 °C. The purpose of this is to investigate the temperature effect on the cone/jet/fiber morphologies that developed. By varying the solution temperature, the chain entanglement status existing in the solution (which is the prerequisite condition for preparing uniform fibers) remained intact. However, the solution properties were significantly altered, thereby giving rise to a feasible route to manipulate the as-spun fiber diameter. By increasing the solution temperature, it was found that the viscosity (η o ) and surface tension (γ) of the PAN/DMF solutions were decreased, but the solution conductivity (κ) was increased; all these trends favored the development of thinner electrospun PAN fibers at high electrospinning temperatures. For instance, with the 6 wt % solutions, PAN fibers with a diameter of 65-85 nm were readily prepared by electrospinning at 88.7 °C, whereas larger fibers with a diameter of 190-240 nm were frequently obtained at room temperature. The temperature dependence of η o , γ, and κ followed the Arrhenius equation, and the corresponding activation energies were composition dependent and found to be ca. 15-28, ∼10 and ∼3.7 kJ/mol, respectively. Hightemperature electrospinning eventually produced PAN fibers with less crystallinity but higher chain orientation as revealed by the wide-angle X-ray diffraction and birefringence measurements. Moreover, the scaling law for the viscosity dependence of fiber diameter, d f , was also altered from d f ) 14.8η o 0.52 (unit: d f in nm and η o in cP) at room temperature to d f ) 3.0η o 0.74 at 88.7 °C, suggesting that high-temperature electrospinning was an effective method to produce ultrathin fibers.

Interactions between silver nanoparticles and polyvinyl alcohol nanofibers

“…2 A prerequisite for fiber formation during electrospinning is the presence of sufficient cohesive force in the working solution to develop a deformable entangled chain structure that prevents jet breakup. 3 Fibers manufactured using this method possess several attractive characteristics such as small diameters, high specific surface areas, flexibility of the surface functionality, high porosities, and so on. Thus, the nanofibers can be used as filter materials, biomedical elements, tissue scaffolds, components of biosensors and photoelectric devices, reinforced composite materials, and so on.…”

Environmentally controlled emulsion electrospinning for the encapsulation of temperature-sensitive compounds

“…However, while producing nanofibers, the environmental conditions (temperature and relative humidity) are strongly influencing the obtained fiber morphology [7][8][9][10][11][12][13].…”

A review on electrospun bio-based polymers for water treatment

“…It was deduced that the increase in temperature reduces the viscosity of the solution and enhances the solvent evaporation, which results in thinner nanofibres [89]. Depending on the system under investigation, two antagonistic effects are observed: (1) reduction in fibre diameters, and (2) increase in diameter which may result in fusion of the nanofibres [90].…”