N-conjugated polymers

Polymers with n-conjugated backbones are an important class of materials that have captured the imagination of the scientific community due to their remarkable properties and exciting applications [91-95]. While most of the work on n-conjugated polymers has focused on all-carbon systems, there has been considerable interest in incorporating heteroatoms into the n-conjugated backbone (i.e.,polythiophene, polypyrrole, polyaniline) to tune their properties. 

Another problem that is common for all membrane-based solid-state sensors is the ill-defined membrane-metal interface. A large exchange current density is required to produce a reversible interface for a stable potentiometric sensor response. One approach to improving this interface is to use conducting polymers. Conducting polymers are electroactive n-conjugated polymers with mixed ionic and electronic conductivity. They... 

Polyarylenevinylene (PAV) expressed by the chemical formula of [-Ar-CH=CH-]n, where Ar is an arylene ring, is an attractive n-conjugated polymer family because of the following features (i) by the thermal conversion from polyelectrolyte or organic-solvent-soluble precursors, one can obtain the PAV films which have large third-order susceptibility and excellent optical quality, and (ii) the band gap can be adjusted by suitable selection of the arylene rings. 

The x(3) values of the PAV cast films were greatly enhanced when the harmonic wavelength was in the absorption region due to n-n transition. This results suggest that the enhancement was caused by the three photon resonance. The maximum x(S) were 0.4 x 10 10 esu at 1475 nm, 1.6 x 10 10 esu at 1600 nm, 4.5 x 10 10 esu at 1900 nm for PPV, MOPPV and PTV, respectively. The values show the tendency that enhancement in x value is accompanied with decrease in band gap of n-conjugated polymer, as theoretically predicted by Wu et al.[34]. 

Scheme 1. Chemical Structures of some important linear n-conjugated polymers. Polyenes 1, poly-ynes 2, polyenynes 3, poly(p-phenylene)s (PPP) 4, polyphenylenevinylenes (PPV) 5, polyphenyleneethynylenes (PPE) 6.

The polaronic strategy has also been applied to polymers, incorporating m-phenylene units as coupling links in n-conjugated polymer chains of polyfthienylene ketone) (Dal Colle et al. 1999) as well as of polyarylamine, polyacetylene, and polythiophene (Kaisaki et al. 1991, Murray et al. 1994, Bushby et al. 1997a). Scheme 1.44 represents these polaronic polymers. 

Yamamoto T (2003) Synlett 425-450 Synthesis of n-conjugated polymers bearing electronic and optical fnnc-tionalities by organometaUic polycondensations. Chemical properties and applications of the n-conjngated polymers... 

Among the n-conjugated polymers, poly(p-phenylenevinylene)s (PPVs) have attracted particular attention since the 1990 report of Friend et al. on... 

Yamamoto T Macromol Rapid Commun (2002) 23 583-606 n-Conjugated polymers with electronic and optical functionalities preparation by organometallic polycondensation, properties, and applications... 

Ley KD, Schanze KS Coord Chem Rev (1998) 171 287-307 Photophysics of metal-organic n-conjugated polymers... 

The electronic properties of n-conjugated polymers reflect well the basic electron-withdrawing or electron-donating properties of the components of the Ti-conjugated polymer [62]. In view of the electrochemical reduction potential, the thiophene unit and tetrathiafulvalene unit (Nos. 8 and 9 in Table 1) have a similar electronic effect in PAEs. It is reported that poly(arylenevinylene)s are also susceptible to electrochemical reduction [63, 64]. Due to the electron-accepting properties, PAEs are usually inert in electrochemical and chemical (e.g.,by I2 [54]) oxidation. 

Control of alignment of n-conjugated polymers on the substrate is important for excellent performance of the polymer in electronic devices (e.g., higher mobility of carrier in field-effect transistors [134,136]). Details of the molecular structure and molecular assembly of PAEs will be discussed in other chapters. 

TABLE 2. Physical Properties of Selected n-Conjugated Polymers"... 

In contrast, the electrical conductivity tends to become higher with a lower silole content, reaching up to 2.4 S cm-1 upon doping with iodine. The bulky (t-butyldimethylsiloxy)methyl side groups in the silole unit are oriented out of the n-conjugated polymer plane and hence hinder the interaction between the polymer chains, which is known to be one of the key factors for high conductivity values174. 

Several n-conjugated polymers and oligomers (polyacetylene, several polythiophenes, Ooct-OPV5 oligomers, and phthalocyanines) have been used for the active layer of the transistors. 

Additional polythiophene n-conjugated polymer precursors were prepared by Reuter [4], (V), and Groenendaal [5], (VI), and used in electroconductive... 

Hayashi H. and Yamamoto T. (1998) New n-conjugated polymers derived from a benzimidazole unit. Preparation, solvatochromism, and oxidation of poly(aryleneethynlene)s composed of 2-(3,5-di-tert buty 1-4-... 

General Features of Doping-Induced Changes in n-Conjugated Polymers 371... 

Classical metals, insulators Ion-radical salts and n-conjugated oligomers Inorganic ir-conjugated polymers and polymerlike carbonaceous materials n-Conjugated polymers Conventional redox-polymers Inorganic ntercatation compounds... 

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