Polyaniline nanostructured template

X. Luo, A. J. Killard, A. Moirin, and M. R. Smyth, Electrochemical preparation of distinct polyaniline nanostructures by surface charge control of polystyrene nanoparticle templates, Chem. Commun., 3207-3209 (2007). 

Chen, W., R. B. Rakhi, and H. N. Alshareef. 2013. Morphology-dependent enhancement of the pseudocapacitance of template-guided tunable polyaniline nanostructures. Journal of Physical Chemistry C 117 15009-15019. 

Using functional molecules as structural directors in the chemical polymerization bath can also produce polyaniline nanostructures. Such structural directors include surfactants [16-18], liquid crystals [19], polyelectrolytes (including DNA) [20,21], or complex bulky dopants [22-24]. It is believed that functional molecules can promote the formation of nanostructured soft condensed phase materials (e.g., micelles and emulsions) that can serve as soft templates for aniline polymerization (Figure 7.3). Polyelectrolytes such as polyacrylic acid, polystyrenesulfonic acid, and DNA can bind aniline monomer molecules, which can be polymerized in situ forming polyaniline nanowires along the polyelectrolyte molecules. Compared to templated syntheses, self-assembly routes are more scalable but they rely on the structural director molecules. It is also difficult to make nanostructures with small diameters (e.g., <50 nm). For example, in the dopant induced self-assembly route, very complex dopants with bulky side groups are needed to obtain nanotubes with diameters smaller than 100 nm, such as sulfonated naphthalene derivatives [23-25], fidlerenes [26], or dendrimers [27,28]. 

Polyaniline nanostructures have been synthesized with specific structural-directing materials added to the polymerization bath including templates (8, 9) or functional molecules 10, II). Both of these methods lead to complex synthetic conditions that require the removal of the templates and/or produce nanostructures with small yields and low reproducibility. Electrospinning is a... 

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. 

X. Yu, Y. Li, and K. Kalantar-zadeh, Synthesis and electrochemical properties of template-based polyaniline nanowires and template-free nanofibril arrays Two potential nanostructures for gas sensors, Sens. Actuat. B, 136, 1-7 (2009). 

There are various methods to synthesize polymer nanostructures, i.e., template synthesis, chiral reactions, self-assembly, interfacial polymerization and electrospinning. Recent developments in conducting polymer nanotubes and nanofibers were summarized by Long et al. Different preparation methods, physical properties, and potential applications of one-dimensional nanostructures of conjugated polyaniline (PANI), pol5 3nrole (PPy) and poly (3, 4-ethylenediox3d hiophene) (PEDOT) were discussed. 

Obviously, STFM is a facile and efficient approach to synthesize polymer, in particular PANI, nanostructures because it not only omits hard template and post-treatment of template removal but also simplifies reagents. However, the self-assembly mechanism of the conductive nanotubes of PANI by the STFM is not yet understood. It might be due to the formation of aniline dimer cation radicals which could act as effective surfactants to shape the polyaniline morphology. 

For some applications, especially in the area of corrosion protection, electropolymerization of polyaniline onto active substrate is of interest. Lacroix and co-workers achieved this by first coating mild steel with a very thin PPy layer and then electrocoating polyaniline on top of this. Others have electrodeposited polyaniline-PPy composites on aluminum or steeP surfaces using oxalic acid electrolytes. A number of ring-substituted anilines have also been directly electrodeposited on active iron substrates using an oxalic acid electrolyte. To create novel nanostructures, polyanilines have been recently deposited on aligned carbon nanotubes or into the interstitial spaces of inverse opals to create novel ordered 3-D networks (Figure 4.2). Molecular templates (such as cyclodextrin) have also been added to electrode surfaces to facilitate electrodeposition of nanostructures. ... 

A.D.W. CarsweU,E.A.O Rea, B.P. Grady, Adsorbed surfactants as templates for the synthesis of morphologically controlled polyaniline and polypyrrole nanostructures on flat surfaces from spheres to wires to flat films. J. Am. Chem. Soc. 125(48), 14793-14800 (2003). doi 10. 1021/ja0365983... 

---