Intrinsic delocalized electrical

Ui is the intrinsic delocalized (resonance) electrical effect parameter it represents the delocalized electrical effect in a system with no electronic demand. 

The intrinsic delocalized (resonance) electrical-effect parameter. It represents the delocalized electrical effect in a system with zero electronic demand, ffe The electronic demand sensitivity parameter. It adjusts the delocalized effect of a group to meet the electronic demand of the system, ffp A composite delocalized electrical-effect parameter which is a function of and (Tj.Examples of Cd constants are the o-r and % constants.The o-r i constants, where k designates the value of the electronic demand q, are also examples of [Pg.435]

Typically, electrical conductivity of EAPs is measured in units of S/cm. Both two- and four-point probe techniques are used to measure a in films and pressed pellets (255). Conductivities as high as 10 S/cm have been reported for several EAPs. Values vary depending on synthetic procedures, fabrication techniques, and measurement methods. EAPs are typically only partially crystalline (256-258) amorphous EAPs have been reported (259-261). Therefore, disorder plays a significant role in their electrical conductivities, and the conductivity arises from the metal-insulator transition (262). As an example, PA with the highest conductivity reported so far shows temperature dependence of conductivity (263). Thus, electrical conductivity is limited by the disorder-induced localization of the electrons rather than by the intrinsic conductivity of the delocalized charges on the polymer backbone. Table 2 shows conductivities for several well-known EAPs (26-28). 

The role of the dopant potential on the stability and magnetic and optical properties of polarons and bipolarons in conducting polymers is shown with the aid of calculations of singlet and triplet states of a bipolaron [167] and by spectroelectrochemical and conductivity measurements [168-170]. The X-band optically detected magnetic resonance of PHT and PDDT shows that the distant intrachain polaron recombination is temperature-independent and identical in films and solutions. However, the triplet polaronic excitation decay is observable in films, but not in solutions [171], Electrochemical in situ conductivity and EPR measurements of PT films were performed in several solutions [172]. The results indicate that polarons merely seem to initiate the electrical conductivity. The electronic delocalization of polarons is restricted to a relatively short chain length at low potentials. As the polaron concentration increases (spin density maximum), bipolarons are generated immediately (probably too fast for the detection of polarons by EPR). Thus the bipolarons prevail in the fully conducting polymer films and as a consequence should be mainly responsible of the intrinsic conductivity [172]. Asymmetrically disub-stituted PBT display well-defined redox processes which are correlated to the consecutive formation of radical cations, dimerized radical cations, and dications [173]. 

Conducting polymers have intrinsic conductivity in the range 10 to 10 Scm due to the presence of delocalized Pl-electrons given by the C-C double bonds in the backbone structure. Their electrical conductivity can be further increased to 10° to 10 Scm by partial oxidation (P-doping) or reduction (n-doping) [51]. To synthesize flexible conducting BC, polyaniline (PAni) and polypyrrole (PPy) have been widely investigated and some of these results are summarized below. 

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