7t-conjugated polymers

Wright, V. A. Patrick, B. O. Schneider, C. Gates, D. P. Phosphorus Copies of PPV 7t-Conjugated Polymers and Molecules Composed of Alternating Phenylene and Phosphaalkene Moieties. ]. Am. Chem. Soc. 2006, 128, 8836-8844. 

Polymers. The 7t-conjugated polymers used in semiconducting applications are usually insulating, with semiconducting or metallic properties induced by doping (see FLECTRICALLY CONDUCTIVE polymers). Most of the polymers of this type can be prepared by standard methods. The increasing use of polymers in devices in the last decade has led to a great deal of study to improve the processability of thin films of commonly used polymers. 

Batteries. Many 7t-conjugated polymers can be reversibly oxidized or reduced. This has led to interest in these materials for charge-storage batteries, since polymers are lightweight compared to metallic electrodes and liquid electrolytes. Research on polymer batteries has focused on the use of polymers as both the electrode and electrolyte. Typical polymer electrolytes are formed from complexes between metal-ion salts and polar polymers such as poly(ethyleneoxide). The conductivity is low at room temperature due to the low mobility of cations through the polymer-matrix, and the batteries work more efficiendy when heated above the glass-transition temperature of the polymer. Advances in the development of polymer electrolytes have included polymers poly(ethylene oxide) intercalated into layered silicates (96). These solid-phase electrolytes exhibit significantly improved conductance at room temperature. 

Poly(iminoborane)s [(-BR=N-)n] are a potential 7t-conjugated polymers, since boron-nitrogen bonds possess the double bond like nature owing to pTt-pjt interaction However, these materials are not fully characterized so far 10>. In order to incorporate the monomeric B-N bond into the conjugation path, we examined an alternating boration copolymerization between diisocyanates and diynes making use of different reactivity between haloboration and phenylboration reactions. 

Since by definition 7t-electrons are extensively conjugated in tltese classes of polymers, it would be much easier for one to oxidize or reduce the polymers rather than their monomeric counterparts. The polymer would act as either an electron source during oxidation or an electron sink during reduction. As a result, the polymers would be electroactive and participate in the electrochemical reactions. For this reason, electrochemistry has been playing a central role in characterizing the 7t-conjugated polymers. 

Many 7t-conjugated polymers can be straightforwardly synthesized using electrochemical techniques in both aqueous and non-aqueous media. As alluded to in the Introduction many polymers have been prepared by electrochemically oxidizing or reducing their monomers under appropriate experimental conditions as long as their monomeric molecules can be oxidized... 

Corrosion protection of semiconductor electrodes [302], 7t-Conjugated polymers act as a protective corrosion inhibitor by depolarizing the electrode surface. A disadvantage is that the polymer could block the light path, which could be important for a semiconductor electrode to undergo a photoelec-trochemical reaction. 

While 7t-conjugated polymers that can be prepared electrochemically in situ on the electrode surface can be characterized rather easily, those that cannot be prepared are more difficult to study. This is because polymer films must be casted in the form of their solutions on electrode surfaces. For a polymer like polyacetylene (PA), it is difficult to dissolve in most organic solvents because of its extremently low solubility. Thus, early studies were carried out with ohmic contacts of pressed pellets of PA with metal current collectors, although PA films were shown to be prepared in situ directly on the electrode surfaces [312], For this reason, electrochemical studies of PA have not been conducted as extensively as for PAn, PPy, PTh, etc., which we discussed rather extensively in the previous section. We discuss the electrochemistry of PA in this section as a representative example of 7t-conjugated polymers, which are not prepared by electrochemical techniques. 

The development of scanning probe techniques, and in particular phase-imaging AFM, created a unique opportunity for researchers to directly study the local crystallinity and inhomogeneity of conducting and semiconducting 7t-conjugated polymers. Early... 

Y. Zhou, H. Itoh, T. Uemura, K. Naka, and Y. Chujo, Synthesis of novel stable nanometersized metal (M=T d, Au, Pt) colloids protected by a 7t-conjugated polymer, Langmuir, 18,277-283 (2002). 

Yamamoto, X, Morita, A., Miyazaki, Y, Maruyama, X, Wakayama, H., Zhou, Z.H., Nakamura, Y., Kanbara, X, Sasaki, S., Kubota, K., 1992. Preparation of Jt-conjugated poly(thiophene-2,5-diyl), polyfp-phenylene), and related polymers using zerovalent nickel complexes. Linear structure and properties of the 7t-conjugated polymers. Macromolecules 25,1214-1223. 

The results reported herein suggest that this method is poised to produce new, well-defined materials that will have a significant impact on the future apphcations of 7T-conjugated polymers. 

Conjngated polymers differ from crystalline semiconductors and metals in several aspects and are often treated theoretically as a one-dimensional system. The formation of the band gap is explained taking into account either electron-phonon interactions or electron-electron interactions among 7t-electrons. If electron-phonon interaction dominates in real 7t-conjugated polymers, these systems could be treated using Peierls theory. In contrast, when electron-electron interactions dominate, the Hubbard model could be used to explain the physical properties of polymers. 

Matsufuji, A., S. Nakazawa, and K. Yamamoto (2001). Electrocatalysis of the reduction of dioxygen by 7t-conjugated polymer complexes with dinuclear cobalt porphyrin. J. Inorg. Organomet. Polym. 11, 47-61. 

Lu W, Fadeev AG, Qi B, Smela E, Mattes BR, Ding J, Spinks GM, Mazurkiewicz J, Zhou D, Wallace GG, MacFarlane DR, Forsyth SA, Forsyth M (2002) Use of ionic liquids for 7t-conjugated polymer electrochemical devices. Science 297 983-987... 

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