Polypyrrole electrospinning

Figure 4.10 SEM micrographs of electrospun nanofibers from (a) aqueous solutions of 1.5 wt% PEO as carrier with PPy content of 71.5 wt%, (b) 7.5wt% [(PPy3) (DEHS) ]x solution in DMF. The scale bar is Igm. (Reprinted with permission from Polymer, Conductive polypyrrole nanofibers via electrospinning Electrical and morphological properties by I. S. Chronakis, S. Grapenson and A. Jakob, 47, 1597-1603. Copyright (2006) Elsevier Ltd)...

A novel route to pure and composite fibers of polypyrrole was recently reported by Han and Shi [42]. An organic salt (FeAOT) was synthesized by the reaction of sodium l,4-bis(2-ethyUiexyl)sulfosuccinate (AOT) and ferric chloride. It was fabricated into nanofibers by manual drawing and electrospinning. Long PPy fibers were obtained for the first time by a vapor deposition reaction of pyrrole on the FeAOT fibers, and this technique was extended to the synthesis of PPy composite fibers with multiwalled carbon nanotubes (PPy-MWCNT fibers). The PPy and PPy-MWCNT fibers had a nanoporous morphology, a conductivity of 10-15 S cm and a tensile strength of 12—43 MPa. Studies of the electrochemistry and current-voltage characteristics of the PPy fibers were also reported. 

Figure 4.12 Schematic illustration of the mechanism for preparing core-shell nanostructured conductive PPy composites. (Reprinted with permission from Materials Letters, Fabrication of Polyacrylonitrile/polypyrrole (PAN/Ppy) composite nanofibers and nanospheres with core shell structures by electrospinning by X. Li, X. Hao, H. Yu and H. Na, 62, 1155-1158.

Dong and Jones Jr. reported on the preparation of submicron electrically conductive polypyrrole/poly(methyl methacrylate) coaxial fibers and conversion to polypyrrole tubes and carbon tubes [47]. In this study, PMMA fibers with an average diameter of 230 nm were initially fabricated by electrospinning as core materials. The PMMA fibers were subsequently coated as templates with a thin layer of PPy by in situ deposition of the conducting polymer from aqueous solution. Hollow PPy nanotubes were produced by dissolution of the PMMA core from PPy/PMMA coaxial fibers. Furthermore, high temperature (1000 °C) treatment under an inert atmosphere can be used to convert PPy/PMMA coaxial fibers into carbon tubes by complete decomposition of the PMMA fiber core and carbonization of the PPy wall (Figure 4.13). 

Extremely low-dimensional conducting nanowires (as small as 3 nm in diameter) for use in nanoelectronics can be produced with the electrospinning technique [103]. Using template methods, insulating PLA fibers with an average diameter of 200-700 nm as core materials were electrospun and subsequently coated with thin 50-100 nm films of polyaniline or polypyrrole by in situ polymer deposition methods. The PLA core fibers decompose upon relatively mild thermal treatment under inert atmosphere, leaving... 

I. S. Chronakis, S. Grapenson, and A. Jakob, Conductive polypyrrole nanofibers via electrospinning electrical and morphological properties. Polymer, 47, 1597-1603 (2006). 

S. Nair, E. Hsiao, and S. H. Kim Fabrication of electrically-conducting nonwoven porous mats of polystyrene-polypyrrole core-shell nanofibers via electrospinning and vapor phase polymerization, J. Mater. Chem., 18, 5155-5161 (2008). 

Y-W. Ju, J-H. Park, H-R. Jung, and W-J. Lee, Electrochemical properties of polypyrrole/ sulfonted SEBS composite nanofibers prepared by electrospinning, Electrochim. Acta, 52, 4841 847 (2007). 

Silver/polypyrrole/polyacrylonitrile composite nanofibrous mats were obtained by applying coating method. AgN03/PAN mats were prepared by electrospinning and the mats were placed into the boiling mixture of pyrrole and toluene. Then the pyrrole was oxidized by silver ions, leading to PPy and elemental Ag. 

Figure 8.6 shows the TEM images of silver/polypyrrole/ polyacrylonitrile composite nanofibrous mats prepared. It was reported that low AgN03 content could decrease the diameters of the Ag/PAN fibers and higher AgNOs concentration led to increase in the diameters of the hybrid fibers due to the high content of the solute in the electrospinning solution. ... 

Li X., Hao X., Yu H., and Na H., Fabrication of polyacrylonitrile/ polypyrrole (PAN/Ppy) composite nanofibres and nanospheres with core-shell structures by electrospinning. Mater. Lett, 2008,62,1155-1158. 

Kang, T.S., et al. 2005. Electrically conducting polypyrrole fibers spun by electrospinning. Synth Met 151 61. 

Although we have been able to electrospin polyaniline into nanofibers, polypyrrole is unable to be processed into homogenous textile fibers since this ICP is insoluble in common organic solvents and infusible, thus making thermal or solution processing difficult. To overcome this limitation. 

The first example is the work of Lu et al. [124] who fabricated polypyrrole (PPy)ATi02 coaxial nanocables, where the conductivity of PPy was integrated with the photocatalytic activity of Ti02 for applications in electrochromic devices, nonlinear optical systems, and photoelectrochemical devices. The synthetic approach consisted in (1) preparation of Ti02 fibers by sol-gel electrospinning and calcination of the polymer (PVP in the specific case), (2) physical adsorption of Fe " oxidant on the surface of Ti02 nanofibers, and (3) polymerization of pyrrole (from vapor) on the surface of Ti02 nanofibers. 

A straightforward method to prepare conductive nanofibrous membrane (NFM) is from the electrospinning of conducting polymers (Figure 13.8), such as polypyrrole, polyaniline, polyethylene oxide, and polythiophene [64, 65]. Electrically conducting polymers are known to possess numerous features, which allow them to act as excellent materials for the development of sensing devices as well as for the immobilization of biomolecules in the design of biosensors [66]. 

Besides water-soluble polymers, more synthetic polymers are insoluble in water and should be dissolved in organic solvent for electrospinning, such as polylactic-co-glycolic acid (PLLA), PCL, polybutylene succinate-co-butylene terephthalate (PBST), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), PAN, poly-sulfone (PSF), polyimide (PI), polyethylene-co-vinyl alcohol (PEVA), PU, polypyrrole (PPy), polyoxymethylene (POM), PS, polymethyl methacrylate (PMMA), PVC, polyvinylidene fluoride (PVDF), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), poly A-vinylcarbazole (PVK), polymeta-phenylene isophthalamide (PMIA), polyethylene terephthalate (PET), polycarbonate (PC), polybenzimidazole (PBI), polymer vinyl acetate (PVAc), polyvinyl butyral (PVB), and polyethylene-co-vinyl acetate (PEV). 

Srivastava et al. [48] demonstrated a microfluidic approach to fabricate hollow and core/sheath nanoflbers by electrospinning. They successfully fabricated hollow PVP + titania (Ti02) composite and core/sheath polypyrrole/PVP nanoflbers in the order of 100 and 250 nm, respectively, using elastomeric microfluidic devices. 

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