Polymer nanostructures nanowires

Figure 10.8 Polymer line fabricated at 10 nm s 48% humidity, -12 V. Polymer line width 30 nm scale bar 250 nm. (Reprinted with permission from Journal of the American Chemical Society, Direct-Writing of Polymer Nanostructures Polyftbiopbene) Nanowires on Semiconducting and Insulating Surfaces by Benjamin W. Maynor et a ., 124, 4. Copyright (2002) American Chemical Society)...

With rapid developments in nanoscience and nanotechnology, various nanostructures, including nanotubes (NTs), nanowires (NWs), and nanopaiticles (NPs), have been fabricated using light-emitting polymers [4-6], The intrinsic characteristics of jr-conjugated polymer nanostructures can be controlled through the physical dimensions, chemical processes, and post-synthetic treatments. 

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 (From Akagi, K., Unpublished data, 2004.)... 

FIGURE 16.4 I-V characteristics of iodine doped PA nanofiber. Znsef shows scanning force microscope image of PA nanofiber on top of Pt electrodes (with 100 nm separation). Typical diameter of PA nanofiber is 16-20 mn (From Park, J.G., et al. Synth. Met., 119, 53, 2001 and Park, J.G., Electrical transport properties of conducting polymer nanostructures Polyacetylene nanofiber, polypyrrole nanotube/nanowire, Ph.D. thesis, Seoul National University, Seoul, 2003.). 

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. 

B. W. Maynor, S. F. Filocamo, M. W. Grinstaff, J. Liu, Direct-writing of polymer nanostructures poly(thiophene) nanowires on semiconducting and insulating surfaces, Journal of the American Chemical Society 2002, 124, 522. 

Nanostructured semiconducting block copolymers containing triphenylamine as hole transport moiety and perylene bisimide as dye and electron transport, have been investigated in view of applications in photovoltaic devices. The polymers show nanowire like structure which formation is driven by the crystallization of perylene bisimides via n- n stacking and since this self-assembly gives rise to domains size comparable to the exciton diffusion length, these materials offer perspectives for the implementation of organic solar cells [357]. 

Schematic of the mechanism of the soft-template synthesis of different conducting polymer nanostructures (a) micelles acted as soft-templates in the formation of nanotubes. Micelles were formed by the self-assembly of dopants, and the polymerization were carried out on the surface of the micelles (b) nanowites formed by the protection of dopants. The polymerization were carried out inside the micelles (c) monomer droplets acted as soft-templates in the formation of microsphere and (d) polymerization on the substrate producing aligned nanowire arrays. Nanowires were protected by the dopants, and polymerization preferred to cany out on the tips of nanowires.

Figure 1.2 Schemes of a few one-dimensional nanostructures that can be reahzed by polymeric materials, (a) Flexible nanofiber (typically made of amorphous polymers), (b) nanowire (frequently made of semicrystalline organics) and (c) nanoribbon. The insets in (b) and (c) show schematics of the corresponding cross-sections of the nanostructures, r. nanowire radius w nanoribbon width h nanoribbon thickness.

There is considerable interest in developing new types of magnetic materials, with a particular hope that ferroelectric solids and polymers can be constructed— materials having spontaneous electric polarization that can be reversed by an electric field. Such materials could lead to new low-cost memory devices for computers. The fine control of dispersed magnetic nanostructures will take the storage and tunability of magnetic media to new levels, and novel tunneling microscopy approaches allow measurement of microscopic hysteresis effects in iron nanowires. 

Similar approach has also been taken by Ferain and Legras [133,137,138] and De Pra et al. [139] to produce nanostructured materials based on the template of the membrane with etched pores. Polycarbonate film was also of use as the base membrane of the template, and micro- and nanopores were formed by precise control of the etching procedure. Their most resent report showed the successful formation of ultrasmall pores and electrodeposited materials of which sizes were as much as 20 nm [139]. Another attractive point of these studies is the deposited materials in the etched pores. Electrochemical polymerization of conjugated polymer materials was demonstrated in these studies, and the nanowires based on polypyrrole or polyaniline were formed with a fairly cylindrical shape reflecting the side wall structure of the etched pores. Figure 10 indicates the shape of the polypyrrole microwires with their dimension changes by the limitation of the thickness of the template. 

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