Conducting Polymer Nanostructures

Abstract

Nowadays, functionalized nanomaterials, which size is 1 100 nm, have been received great attention in nanosciences and nanotechnology because of their large surface area. Compared with their bulk materials, moreover, nanomaterials are advantageous of hollow structures. Therefore, the nanotubes or hollow nanospheres can be served as " nanoreactors " , allowing chemical reaction carries out inside of the nanotubes or hollow spheres. Furthermore, multi-functionalized composite nanostructures are easily fabricated by coating other materials on the surface of the nanotubes or filling metal nanoparticles inside of the nanotubes. As demonstrated in Chapters 1 3, conducting polymer nanostructures have unique properties such as S-conjugation polymeric chain, metal-like conductivity, reversible physical properties by a novel doping/de-doping process that can be used as molecule wires and nanodevices, resulting in attracting attention in nanosciences and nanotechnology. For the conducting polymer nanostructures, however, some basic issues are necessary to be solved: (1) To search simple and efficient methods to synthesize or prepare conducting polymer nanostructures and to understand formation mechanism of various methods. (2) To character molecular structure and to measure physical properties of the conducting polymer nanostructures, especially finding difference from their bulk materials and understanding their origin. (3) Since the size of nanomaterials is in a range of 1 100 nm, influence of size on the physical properties must be considered, which is called as size effect. (4) To search fabrication technology and to improve properties of nanodevices made of conducting polymer nanostructures. (5) To realize commercial application of conducting polymer-based nanodevices in technology. Discussions of this chapter are dealing with above-mentioned issues and following an order of synthetic method and formation mechanism, composite nanostructures, as well as physical properties and applications. 4.1 Synthetic Method and Formation Mechanism Searching facile and efficient synthetic method is a basic and an important object for the conducting polymer nanostructures. Up to date, hard template and soft template method as well as physical methodologies (e.g. electro-spinning technique) have been employed to synthesize conducting polymer nanostructures and their Chapter 4 Conducting Polymer Nanostructures 89 composite nanostructures. In the hard template method, porous membrane is required as a hard template that guides growth of the nanostructures within the pore in the membranes, leading to completely controlling nanostructures in morphology and diameter dominated by morphology and size of the pores. Since the hard template is often removed after polymerization in order to obtain pure nanostructures, resulting in complex preparation procedure. In the soft template method, super-molecule self-assembled via hydrogen bonds, S S stacking interactions, Van der Waals force and electrostatic interaction as the driving forces instead of the hard-template to grow the nanostructures. Therefore, the soft-template method is simpler than that of the hard template method owing to omitting the membrane as a hard template and post-treatment of removing template. Since the formation super-molecule as a soft-template is often affected by the reaction conditions, thus controllability of the soft-template synthesized nanostructures is lack compared with hard-template method. On the contrary, the less controllability of soft-template method might properly provide a great chance to prepare complex three-dimensional (3D) micro/nanostructures self-assembled from one-dimensional (1D) nanostructures, which is unable for the hard template method, because only cylindrical pores are available in the commercial membrane as a hard template. Besides, electro-spinning technique as a physical method has been used to fabricate conducting polymer nanofibers. However, it is difficult to prepare pure conducting polymer nanofibers due to their low viscosity dissolved in organic solvent. Thereby this method is generally used to fabricate composite nanofibers of conducting polymers. In this section, different synthesis methods and formation mechanism for resultant conducting polymer nanostructures and their composite nanostructures are reviewed in detail.