Preparation of ultrafine uniform electrospun polyimide nanofiber

Abstract

This paper reports the preparation of bead-free ultrafine uniform nanofibers with a narrow fiber diameter distribution from fluorinated polyimide by electrospinning. Increasing the electrical conductivity of polymer solutions by the addition of salts and decreasing the discharge rate of water from the polymer by decreasing the humidity in the surrounding air decreases the diameter of the electrospun nanofiber. Ultrafine uniform nanofibers were achieved using these new salt and humidity conditions, and we successfully prepared bead-free ultrafine uniform nanofibers with a narrow range of nanoscale diameters (33±5 nm). Polymer Journal (2010) 42, 514-518; doi:10.1038/pj.2010.33; published online 28 April 2010Keywords: electrospinning; fluorinated polyimide; humidity; nanofiber; salt INTRODUCTION Nanoscale fibers prepared by the electrospinning method have received a great deal of attention, as electrospinning is capable of producing fibers with diameters in the nanometer range. 1-4 Electrospun nanofibers possess many unique properties including a large specific surface area and superior mechanical properties, and they have potential use as nanoscale building blocks. Nanofibers have been successfully prepared for many applications such as filters, optical and chemical sensors, catalyst systems, scaffolds for tissue regeneration and immobilized enzymes. 5-10 However, the applications are currently somewhat limited by the fact that most electrospun nanofibers are in the form of nonwoven mats composed of disordered nanofibers. Aligned nanofibers can be used in a variety of electrical, optical, mechanical and biomedical applications.Recently, we reported the synthesis of novel nanofibrous fluorinated polyimide membranes using an electrospinning method on a specially designed collector composed of conductive aluminum plates and glass insulator materials that can be removed from the apparatus. 11 The electrospun nanofibers were deposited across the plates and uniaxially aligned to the collector. In addition, multilayer stacked nanofibrous membranes consisting of three-dimensionally ordered nanopores were produced, and the water flux properties of the nanofibrous membranes were measured. The distance between the uniaxially aligned nanofibers decreased with deposition time, and the collector resulted in square nanopores with a regular diameter of approximately 200 nm. The nanopores prepared by the uniaxially aligned nanofibers had a significantly more regular structure than that formed by nonwoven nanofibers.The nanopore size or the distance between the uniaxially aligned nanofibers strongly depended on the nanofiber diameter. Many papers report a uniform nanofiber without beads with a diameter of

Effects of poly(ethylene oxide) and ZnO nanoparticles on the morphology, tensile and thermal properties of cellulose acetate nanocomposite fibrous film

“…These results suggested that the fine morphology of the electrospun fibers can be successfully created by the proper modulation of the solution properties; similar results have also been reported by other researchers. 9,17,[19][20][21][22][23][24][25] The Fourier-transform infrared spectra of the electrospun CA fibers showed a strong ester carbonyl stretching vibration at 1750 cm À1 , 26 whereas those of PEO fibers exhibited strong peaks at 2900 cm À1 that were attributed to the molecular stretching of methylene groups (CH 2 ). 9 The Fourier-transform infrared spectra of the CA-PEO fibers exhibited both of these characteristic peaks, as shown in Figure 4.…”

Carbon nanofibers prepared from electrospun polyimide, polysulfone and polyacrylonitrile nanofibers by ion-beam irradiation

“…The other appropriate electrospinning conditions, including applied voltages, feeding rate, distance between the spinneret and the collector, and relative humidity, were 15-30 kV, 0.12-1.2 ml hr À1 , 10-20 cm and 5-10% relative humidity, respectively. 13,14,16,17 It was also found that using a polymer concentration that was too low or too high gave mixtures of nanofibers and beads or thick fibers, respectively. On the basis of our knowledge, the optimal electrospinning conditions for 6FDA-APPS, PSF and PAN were carefully studied.…”

“…[8][9][10][11][12] We have succeeded in preparing uniform non-beaded nanofibers with diameters of B30 nm by controlling the processing parameters, including applied voltage, feed rate, electrospinning humidity, and polymer solution viscosity and electrical conductivity. 13,14 The productivity of nanofibers by the electrospinning method is sufficiently high to supply industrial applications by using non-nozzle type spinnerets and/or rotary drum collectors. The configuration of nanofiber assembly can also be controlled from nonwoven nanofibrous membranes to aligned nanofibers.…”

“…We chose polyimides and PSF for several reasons: they easily provide nanofibers by the electrospinning method [13][14][15][16] and have distinctive thermal and mechanical properties that may help to maintain the nanofiber structures after ion-beam irradiation. 17 PAN was chosen because there have been many reports on carbon fibers prepared from PAN fibers by thermal carbonization.…”

Electrospinning of radical polymers: redox-active fibrous membrane formation

“…These materials have attracted much interest for use as sensors, filters and tissue engineering scaffolds, and drug delivery membranes, among other applications. [12][13][14][15][16][17] In the electrospinning process, a viscous, entangled polymer solution is ejected through a syringe toward a grounded target under the application of a high electric potential (typically 10-30 kV). The droplet of solution stretches into a thin jet during flight, and solvent evaporates rapidly from the jet, reducing its diameter and increasing the charge density on the surface.…”