Fiber electrospun

Normal transmission IRLD can also be used to characterize polymeric fibers, although scattering can induce sloping baselines. Raman spectroscopy then becomes a convenient alternative. Rutledge et al. have recently probed the orientation in electrospun nanofibers composed of a core of Bombyx mori fibroin and an outer shell of poly (ethylene oxide) [24], The orientation values were low, less than 0.1, as is often the case in electrospun fibers. 

Figure 12.7 Photographs of electrospun fiber mats embedded with 1 (a) before and (b) after 254-nm UV irradiation (1 mW/cm ) for 3 min. (c) Scanning electron microscopy image of the microfibers containing polymerized 1. (c) Photographs of the polydiacetylene-embedded electrospun fiber mats prepared with various diacetylene monomers after exposure to organic solvent. Reprinted fi om Yoon et al. (2007). Copyright 2007 American Chemical Society. (See color insert.)...

Yoon J, Chae SK, Kim J-M. Colorimetric sensors for volatile organic compounds (VOCs) based on conjugated polymer-embedded electrospun fibers. J Am Chem Soc 2007 129 3038-3039. 

Fig. 9 Cell-fiber sandwiches can be constructed by LbL cell/fiber assembly. The cells are sandwiched between layers of electrospun fiber mashes. The mesh thickness and cell loading can be controlled within this process. Reprinted, with permission, from [190] copyright (2009) Mary Ann...

Figure 9 The electrospun fiber of fibroin (a) and the correlation between the concentration of fibroin and the diameter of electrospun fiber (b).

PVA is also one of the most studied polymers to produce fibers by electrospinning. PVA/CNTs electrospun fibers have first been reported in 2005 (43) and the interaction between PVA and nanotubes in these particular fibers was studied in 2007 (44). A mixture of purified MWNTs and water is sonicated and then added to a PVA solution. The resulting dispersion is electrospun via a voltage of 20 kV. This leads to the production of very thin fibers of typically 300 nm in diameter, as shown in Figure 11.3. 

Figure 11.3. SEM image of PVA/MWNT electrospun fibers. The scale bar is 1pm. Reprinted with permission from reference (44).

A comparison of the diameter of the electrospun fibers with the electrical conductivity of the solutions was shown in Figure 6. There was a significant drop in the diameter of the electrospun polymer fibers when the electrical conductivity of the solution increased. Beads were also observed due to low eonductivity of the solution, which results in insufficient elongation of a jet by eleetrieal foree to produce uniform fiber. 

At 8% concentration less than 30 nm diameter fibers were formed with beads (drops of polymer over the woven mesh) and they were not uniform and were branched off (Figure 23). At 10% eoneentration with 5 em spinning distanee and 2, 3 and 4 kV/em eleetrie fields, drops were formed instead of fibers. Continuous fibers were obtained above 12% regardless of eleetrie field and distanee (Figures 22 and 23). At 19.5%, the average fiber diameter was much larger than that of fibers spun at lower eoneentrations. In the short distanee as well as low concentration (10%), the solution reaehes the eolleetion plate before the solvent fully evaporates. This explains the formation of droplets and beads at the low eoneentration and distanee. Fewer beads were observed in electrospun fibers at higher concentration. 

PW. Gibson, HE. Schreuder-Gibson, D. Riven. 1999.Electrospun fiber mats transport properties. AIChE J., 45(l).pp. 190-195. 

Fig. 4.7 FV height left) and force images right) of electrospun fiber of PVA on SAM of octadecanethiol. The data was acquired with unmodified AFM tips in air. The gray scale denotes bright low forces) to dark (high forces), —4 nN to —30 nN. With kind permission from Springer Science+Business Media [25], Copyright 2005. Springer-Verlag...

Doshi J, Reneker DH (1995) Electrospinning process and applications of electrospun fibers. J Electrostal 35(2-3) 151-160... 

Casper CL et al (2005) Functionalizing electrospun fibers with biologically relevant macromolecules. Biomacromolecules 6(4) 1998-2007... 

Electrospun Fibers as Substrates for Peripheral Nerve Regeneration... 

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