Properties of Polyaniline

Films of optically active PAn salts, such as PAn/(+)-FlCSA 4 or the optically active EB derived from them, have recently been shown49 to exhibit discrimination toward chiral compounds such as the enantiomers of CSA- and amino acids. The studies suggest that these novel chiral materials may indeed have potential for the separation of enantiomeric chemicals, such as chiral drugs. 

The mechanical properties of PAn differ considerably between the electrochemi-cally prepared polymer and that produced from solvent casting. As described earlier, electropolymerized emeraldine salts are highly porous and, consequently, have low mechanical strength. Freestanding films may be prepared electrochemically, but their poor mechanical properties limit their usefulness. In contrast, the polymers made from solution are much less porous and are widely used as freestanding films and fibers. The effect of polymer structures and morphology on PAn mechanical properties are described in the following text. 

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The acid-base properties of polyaniline can be utilized to produce solid-state pH sensors where polyaniline works both as the pH-sensitive material and as the ion-to-electron transducer. An excellent example is the electrodeposition of polyaniline on an ion-beam etched carbon fiber with a tip diameter of ca. 100-500 nm resulting in a solid-state pH nanoelectrode with a linear response (slope ca. — 60mV/pH unit) in the pH range of 2.0-12.5 and a working lifetime of 3 weeks [104]. The response time vary from ca. 10 s (around pH 7) to ca. 2 min (at pH 12.5). 

The rationale for preparing this hybrid copolymer was to combine the desirable properties of polyaniline with those of polythiophene. For example, polythiophene has demonstrated thermo- and electrochromism, solvatochromism, luminescence, and photoconductivity while polyaniline has demonstrated reversible protonic dupability, excellent redox re-cyclability, and chemical stability. 

This analysis technology was applied to screening of chemosensitive properties of polyanilines and copolymers of anilines and aniline derivatives. Combinatorial libraries were prepared by electrically addressed polymerization.42 43 Gaseous hydrogen chloride was selected as an analyte. The measured signal was electrical resistance detected simultaneously by 2 and 4-point techniques (s24 technique44,52), and the ratio of these values provides information on the contribution of the polymer/contact resistance into the total resistance measured by 2-point configuration. 

As with polypyrrole (PPy), the electrical, chemical, and mechanical properties of polyaniline (PAn) are inextricably linked. In addition, PAn has spectacular optical and chromic properties that distinguish it from other conducting electroactive polymers (CEPs). The current state of knowledge concerning properties of PAn is reviewed in this chapter. 

The polymerization potential has also been found to influence the mechanical properties of polyaniline PAn/HA emeraldine salt films.50 The most extensible films were formed at a polymerization potential of 0.65 V (versus Ag/Ag+), which displayed an extension to break of around 40%. Preparation of the PAn/HA films at 0.8 V and 1.0 V resulted in more brittle films. It was suggested that degradation of the PAn at polymerization potentials in excess of 0.8 V might explain the poor properties of the 1.0 V film. The difference in behavior of the films prepared at 0.65 V and 0.8 V was attributed to differences in their crosslink density. Unfortunately,... 

Some physical effects such as moisture absorption [49], temperature [50], protonation level [50], electron localization (polyorthotoluidine) [5la,b], polyaniline [52], crystallinity [53], elongation [54a,b,55] on microwave properties of polyaniline have been found through characterisation with the perturbation cavity method [56], Other methods have been employed and compared with the former one, such as microwave impedance bridge in the X-band (8.2-12.4 GHz) [57] or APC 7 standard (130 MHz-18 GHz) [47] with good agreement. 

Potential applications of the electromagnetic properties of polyaniline have been discussed [81-83], New polymers such as poly-/j-phenylene-benzobis-thiazole [20] have also been investigated. Tuning at 9 and 10 GHz has been obtained with this class of material. Double and single-layer Salisbury screens using PBT vrere fabricated [19]. An absorption of 90% was... 

In this section we will present the models used to describe relaxation phenomena in polymers or other materials. Then, we will present the special case of conducting polymers and the physical origin of the relaxation will be outlined. We will then propose a model able to explain the microwave properties of polyaniline samples. Experimental results concerning the effect of structural parameters of conducting polymers will be given at the end of this section. 

Ram M. K., Salerno M., Adami M., Farad R, and Nicolini C., Physical properties of polyaniline films Assembled by the layer-by-layer technique, Langmuir, 15, 1252-1259, 1999. 

Polyaniline Nanostructures 63 2.3.2 Structure and Properties of Polyaniline Nanotubes... 

P. Dallas, D. Stamopoulos, N. Boukos, V. Tzitzios, D. Niarchos, and D. Petridis, Characterization, magnetic and transport properties of polyaniline synthesized through interfacial polymerization. Polymer, 48, 3162-3169 (2007). 

M. Deepa, S. Ahmad, K. N. Sood, J. Alam, S. Ahmad, and A. K. Srivastava, Electrochromic properties of polyaniline thin film nanostructures derived from solutions of ionic Uquid/ polyethylene glycol, Electrochim. Acta, 52, 7453-7463 (2007). 

S. W. Phang, M. Tadokoro, J. Watanabe, and N. Kuramoto, Effect of Fe304 and Ti02 addition on the microwave absorption property of polyaniline micro/nanocomposites, Polym. Adv. Technol, 20, 550-557 (2009). 

V. Mottaghitalab, G.M. Spinks, and G.G. Wallace, The influence of carbon nanotubes on mechanical and electrical properties of polyaniline fibers, Synth. Met., 152, 77-80 (2005). 

A.P. O Mullane, S.E. Dale, J.V. Macpherson, and P.R. Unwin, Fabrication and electrocata-lytic properties of polyaniline/Pt nanoparticle composites, Chem. Commun., 1606-1607 (2004). 

Y. Long, Z. Chen, J.L. Duvail, Z. Zhang, and M. Wan, Electrical and magnetic properties of polyaniline/Fe304 nanostructures, Physica B Cond. Matter 370, 121-130 (2005). 

S.L. Zhang, R. Tang, and J.Q. Kan, Effect of magnetic field and rare-earth ions on properties of polyaniline nanoparticles, J. Appl. Poly. Sci., 103, 2286-2294 (2007). 

S.L. Mu, Novel properties of polyaniline nanofibers coated with polycatechol, Synth. Met., 156, 202-208 (2006). 

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