Functionalized conducting polymers

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Fig. 7. Schematic representation of enzyme covalently bound to a functionalized conductive polymer where ( ) represents the functional group on the polymer and (B) the active site on the enzyme (42). Courtesy of the American Chemical Society.

AJ Heeger and G Yu, Dual Function Conducting Polymer Diodes, U.S. Patent 5,504,323, 1996. 

PNA strand, resulting in an increase of the electrochemical signal (SWV peak current) as a result of probe-target hybridization. The PNA-functionalized conductive polymer sensor allowed for a detection limit of approximately 10 nM, and the feasibility for single-nucleotide mismatch detection was also demonstrated. 

Solid-state ion sensors with conducting polymers as sensing membranes have also proved useful in some applications. Of particular importance are the pH sensors based on polyaniline that can be also applied in non-aqueous solutions. Polypyrrole-based sensors for nitrate also show great promise for water analysis. However, in addition to these two excellent examples, a large number of functionalized conducting polymers have been synthesized already, and these materials may offer unique possibilities for fabrication of durable, miniaturized ion sensors. 

A last important aspect of these functionalized conducting polymers concerns their interest for the theoretical modelling of the mode of operation of modified electrodes. Previous work based on redox polymer coated electrodes raised a fundamental question concerning the transport of charge in these polymeric materials. 

Lee T. and Shim Y., Direct DNA hybridization detection based on the oligonucleotide-functionalized conductive polymer. Anal. Chem., 73, 5629-5632, 2001. 

Long-range Jhh couplings have been observed in the spectra of novel -(styryl)terthiophenes, the key building blocks in the synthesis of functionalized conducting polymers. ... 

K. Ramanathan, M.A. Bangar, M. Yun, W. Chen, N.V. M3umg, and A. Mulchandani, Bioaffinity sensing using biologically functionalized conducting-polymer nanowire, J. Am. Chem. Soc., 127, 496-497 (2005). 

M.A. Rahman, N.-H. Kwon, M.-S. Won, E.S. Choe, and Y.-B. Shim, Functionalized conducting polymer as an enzyme-immobilizing substrate An amperometric glutamate microbiosen-sor for in vivo measurements. Anal. Chem., 77(15), 4854-4860 (2005). 

A.D. Aguilar, E.S. Forzani, X.L. Li, N.J. Tao, L.A. Nagahara, I. Amlani, and R. Tsui, Chemical sensors using peptide-functionalized conducting polymer nanojunction arrays, Appl. Phys. Lett., 87, 193108 (2005). 

Enzyme electrodes have been constructed by covalent immobilization of enzyme on functionalized conducting polymers, such as poly(3-aminopyrrole). ... 

FUNCTIONALIZED CONDUCTING POLYMERS TOWARD MOLECULAR DEVICES... 

The resulting functionalized conducting polymers display their native functions the functionalities and the conducting properties are not much reduced. Table 1 shows some examples. 

Chemical polymerization methods are also available for preparation of functionalized conducting polymers. Several techniques are shown in Table 2. In these cases, all kinds of functional molecules (negatively charged, neutral, positively charged) can be incorporated. 

Utilizing these functionalized conducting polymers, a solar cell, an electrochromic device, a chemical luminescent material, a sensor, a polymer battery, etc. can be constructed, in which the functionality is attributed to the incorporated functional molecule. 

Gupta B. and Prakash R., Synthesis of functionalized conducting polymer "polyanthranilic acid" using various oxidizing agents and formation of composites with PVC, Polym. Adv. TechnoL, 2011, 22, 1982-1988. 

Gamier, F. 1989. Functionalized conducting polymers-towards intelligent materials. Angew Chem Int Ed Eng 101 529-533. 

Pioneering works on functional molecules incorporating conducting polymers firstly demonstrated them as modified electrodes, on which redox molecules such as ruthenium tetraoxide [1] for photo-oxidation of water, mesotetrakis (4-sulphonatophenyl)porphyrin cobalt [2] and iron phthalocyanine [3] for redox catalysis, were incorporated chemically or electrochemically in polypyrrole conducting polymer. They suggested that functionalized conducting polymers should show the native function of a functional molecule while maintaining the native conductivity without a big decrease. 

Chemical polymerization methods are also available for preparation of functionalized conducting polymers. Several techniques are shown in Table 9.1. The vapour/liquid interface chemical polymerization is recommended to obtain a thin and highly transparent membrane (film) (Table 9.1 (3)) [8]. On the other hand, utilizing an appropriate support which contains any kind of functional molecule, the functional molecule incorporating conducting polymer membrane, as well as a simple conducting polymer, is obtained by the methods illustrated in Table 9.1 (4). By these methods, it is possible to... 

Table 9.2 Functionalized conducting polymers and their functions... 

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