MEH-PPV nanofiber

Poly[2-methoxy-5-(2 -ethyl-hexyloxy)-l,4-phenylene vinylene] (MEH-PPV) is an excellent conjugated polymer and broadly used in polymer photoelectron devices, but is difficult to electronspin directly. In the work by Zhao et al, core-shell structured nanofibers were fabricated by coaxial electrospinning MEH-PPV (shell) in chlorobenzene and PVP (core) in 1,2-dichloroethane [64]. MEH-PPV was soluble in the above two solvents, which prevented the precipitation of MEH-PPV and enhanced the adhering action between the two polymers in the coaxial electrospinning process. It should be noted that this is an unusual example of core-shell nanofibers where (a nonprocessable) PPV was spun as the shell and not in the core. These uniform core/shell PVP/MEH-PPV nanofibers with a highly fluorescent property can have potential applications in the fabrication of polymer nanophotoelectron devices. 

Figure 6.11 Cycles of photo-conductivity (here, a, black curves) for a phototransistor based on an electrospun MEH-PPV nanofiber. Vds = -50 V, Vas = 0 V. Pi incident light intensity (red curves highlighting the on-off illumination eycles). The transistor channel width is 0.5 pm (a), 5 pm (b), 40 pm (c) and 80 pm (d). Reproduced with permission from Ref. 195, Appl. Phys. Lett., 2011, 98, 023307. Doi 10.1063/ 1.3534803. Copyright 2011, American Chemical Society.

H-C. Chen, C-T. Wang, C-L Liu, Y-C. Liu, and W-C Chen, Full color light-emitting electrospun nanofibers prepared from PFO/MEH-PPV/PMMA ternary blends, J. Polymer Sci. B Polymer Phys., 47, 463 70 (2009). 

Moreover, the extended polymer chains should be oriented along the fiber axis due to the strong stretching of the liquid jet during electrospinning better n electron delocalization. In the absorption spectra of MEH-PPV/PFO blend nanofibers a 20-30 nm red shift of the PFO absorption band to 400-410 nm was observed, suggesting that the PFO chains are also extended and oriented along the fiber axis. ... 

The morphology can be controlled using poly(vinyl alcohol) (PVA)/PPV precursor polymers [153,154]. The morphology of fibers can be characterized by scanning electron microscopy and fluorescence microscopy. The fluorescence spectra of PVA/PPV nanofibers and of composite nanofibers made from PPV/MEH-PPV exhibit an appreciable blue-shift, a stronger intensity of fluorescence, and a higher surface photovoltage in comparison to bulk material [154,155],... 

FIGURE 16.2 SEM images o (a) polyacetylene nanofiber ropes. (From Park, J.H., Electronic and scanning tunneling spectroscopic studies of conducting polymer nanostructures Polyacetylene nanofibers, PPV nanotubes and MEH-PPV nanowires, Ph.D. thesis, Seoul National University, Seoul, 2004.) (b) R-helical polyacetylene nanofiber ropes. (From Akagi, K., Unpublished data, 2004.)... 

MEH-PPV thin strip FETs [32], DNA—templated SWNT FETs [99], and some other lowdimensional structures [1]. To evaluate the field-effect mobility (/afet) of polymer nanofiber one can consider the relatively low voltage region of the I-V characteristics in terms of the linear region in conventional MOSFETs. Then from the transconductance, the /Afet can be estimated [82] as... 

Park, J.H. 2004. Electronic and scanning tunneling spectroscopic studies of conducting polymer nanostructures Polyacetylene nanofibers, PPV nanotubes and MEH-PPV nanowires. Ph.D. thesis, Seoul National University, Seoul. 

Recently, there have been some attempts to prepare PPV nanowires and nanotubes by electrospinning [380-382]. Electrospim nanofiber consisted of a binary blend of poly[2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) with regioregular P3HT or poly(9,9-dioctylfluorene) [380]. The resultant nanofiber was found to have the diameter of ca. 100-500 nm with tunable optical and charge transport properties. In this manner, electro-spiiming has been a powerful technique to fabricate polymer, ceramic and inorganic nanowire. Nanotubular structiu e and coaxial nanowire composite could be also fabricated with blend of soluble core and insoluble wall material by the electrospinning method. 

Madhugiri, S., A. Dalton, J. Gutierrez, J. P. Ferraris, and K. J. Balkus, Jr. (2003). Electrospun MEH-PPV/SBA-15 composite nanofibers using a dual syringe method. Journal of the American Chemical Society 125(47) 14531 -14538. 

Electrospinning of the blends of MEH-PPV and PVP in individually prepared solutions by using a coaxial two-capillary spinneret has been reported [55, 56]. Instead of such polymers, electrospinning of the mixture of polymer precursor and PVP followed by the polymerization had also been reported to prepare uniform nanofibers [57, 58]. Extraction of PVP out from the electrospun fibers in those techniques can be carried out easily, but the design of the spinneret for the first case and the post-thermal conversion of PPV precursor to PPV for the later one are quite complicated. 

We have first reported organic solar cells made of electrospun conducting nanofibers from a derivative of PPV (i.e., MEH-PPV) in 2008 [59]. MEH-PPV... 

---