Polymeric nanofibers

Pol5mier nanofibers exhibit several properties making them favorable for different applications. Nanofibers have a high specific surface area due to their small diameters, and nanofiber mats can 

Polymer nanofibers can be obtained by applying electrical force at the surface of a polymer solution. A charged jet is ejected to the tip of the needle, and the jet extends, bends, and then follows a looping and spiraling path due to the action of the electrical field. It becomes very thin, until it reaches the collector. Nanofibers thathave diameters from several nanometers to hundreds of nanometers can be obtained in the form of nonwoven fiber mats. The small diameters lead to a large surface-area-to-mass ratio, a porous structure with excellent pore interconnectivity, and extremely small pore dimensions. 

In fuel cells, well known catalyst is produced from carbon black-supported Pt particles (Pt/C) for hydrogen and oxygen redox reactions which occurs at anode and cathode but conventional Pt/C catalyst has low durability and can be easily poisoned by carbon monoxide. Electrospun Pt/ruthenium, Pt/rhodium, and Pt nanowires have been produced and compared with Pt/C showing better performance in a proton exchange membrane fuel cell (PEMFC). 

The combination of electrical properties with good mechanical performance is of particular interest in electroactive pol5mieric technology. Fibers have an intrinsically high structure factor, which results in lower percolation threshold values, avoiding material fracture with low filler content Also, the use of mechanically stronger fibers will result in stronger composites. 

The electrical performance of conjugated fiber composites is investigated in the gelation process in a pol5mier after crosslinking, where the conductive network corresponds to the gel fraction. If a fiber segment is able to conduct it must be connected to the gel in both ends. 

---

Pascault, J., Sautereau, H., Verdu, J., and Williams, R. 2002. Thermosetting Polymers. Dekker, New York. Reneker, D.H. and Fong, H. 2006. Polymeric Nanofibers. Oxford University Press, New York. 

Polymer-supported Ag nanoparticles have been widely investigated and provide potential applications as catalysts, photonic and electronic sensors, wound dressings, body wall repairs, augmentation devices, tissue scaffolds, and antimicrobial filters [15-22]. For these applications, Ag nanoparticles have to be supported in a biocompatible polymer system [23-26]. The electrospinning technique has often been adopted for the incorporation of Ag nanoparticles into polymer porous media. In this chapter, we review the preparation methods and properties of Ag nanoparticles incorporated into polymeric nanofibers and their applications in the fields of filtration, catalysis, tissue engineering and wound dressing. 

The present volume entitled, Biomedical Applications of Polymeric Nanofibers attempts to provide a broad overview on the preparation techniques, structures and biomedical applications of different biopolymeric nanofibers. The book consists of 9 chapters ... 

Subbiah, T. and Ramkumar, S.S., 2004b, Polymeric nanofibers by electrospinning. Proceedings of International Conference of High Performance Textiles and Apparels, Coimbatore, India, pp. 81-90. 

Pham, Q. R, Sharma, U., and Mikos, A. G, Electrospinning of polymeric nanofibers for tissue engineering apphcations A review. Tissue Eng, 12, 1197, 2006. 

S. Jang, M. Khil, V. Seshadri, M. Marquez, P. T. Mather, and G. A. Sotzing, Electrospinning of electrochromic conductive polymeric nanofibers. Polymer Preprints, 46, 513-514 (2005). 

Pham, Q.R Sharma, U. Mikos, A.G. Electrospinning of polymeric nanofibers for tissne engineering applications. Tissue Eng. 2006,12 (5), 1197-1211. 

Graham, K., Ouyang, M., Raether, T., (jrafe, T., McDonald, B., andKnauf, P. Polymeric Nanofibers in Air Filtration Application, Fifteenth Annual Technical corference and Expo of the American Filtration and Separations Society. Galveston, Texas, pp. 9-12 (April, 2002). 

There are several techniques that allow to produce polymeric nanofibers, such as drawing, template synthesis, phase separation, self-assembly, solution blow spinning, and electrospinning. The drawing process requires a polymer with appropriate viscoelastic properties that is able to be deformed and kept connected by cohesive forces. Besides being simple and inexpensive, this technique is very limited for conjugate polymers, since most of them have lower solubility and form solutions with a small viscous modulus. 

Electrospinning based on the application of a static electric field on a polymer solution or melt through a spinneret appears to be a simple and well-controllable technique able to produce polymeric nanofibers. A typical experimental setup is based on a capillary injection tip, a high-voltage source able to apply electric fields of 100-500 KVm , and a metallic collector, or counter electrode. Electric current in electrospinning experiments is usually in the order of a few milliamperes. ... 

---