Interchain transfer

Three-dimensional coupling is characterized by the interchain transfer integrals tx. Generally, only nearest-neighbor interactions are taken into account, so only one or two t are relevant. They may differ, even in sign, depending on the relative positions of the interacting chains. In this qual-... 

Band Structure Calculations and Experimental Results The spectroscopic properties discussed above are related primarily to intrachain electronic structure. One exception is the stability of gap states (e.g., polarons) versus the three-dimensional interaction effects mentioned in Chapter 11, Section IV.D. Energy and charge transport are, of course, dependent on interchain transfers. So while there are only a few three-dimensional band structure calculations (e.g., for PA [184] and PPV [185]), there are many theoretical calculations concerning infinite perfectly periodic one-dimensinal chains, the effects of local perturbations, and the elementary excitations of these chains solitons, polarons, and bipolarons. Only a few hints of that work will be given here. It has been discussed and reviewed several times (see, e.g., Refs. 186 to 188). 

In fact, for conjugated polymers, E results from a combination of a and tr bonds (the latter being equal to t ) and E,j is dominated by the interchain transfer integral, Thus, the inequalities imply that, quite generally, the conductivity and the mechanical properties will improve in a correlated manner as the degree of chain alignment is Increased. This prediction is in excellent agreement with data obtained from studies of the poly(3-alkylthiophenes), the poly(phenylene vinylenes), poly(thienylene vinylene) and polyacetylene [27]. 

The ratio km/ gp is also an important parameter of grafting since it characterizes the relationship between the rate of intra- and interchain transfer of hydrogen from chains to the grafted monomer and the rate of monomer attachment to the grafted macroradical. The higher the ratio, the shorter is the length of grafted... 

This effect can be explained by taking into account the interchain and intrachain transport phenomena in the conduction mechanism. It can easily be understood that a high molecular weight polymer is going to provide interchain transfer rates lower than those provided by a shorter polymer. Intrachain conduction will therefore be enhanced. Now, it has been theoretically shown that intrachain conductivity is greater than interchain conductivity, the latter being the limiting parameter of the macroscopic conductivity [165]. 

Table 2. Intrachain and interchain transfer integrals (meV) for PFg, AsFg and SbFg salts. 

Yamashiro and co-workers have estimated the dopant-chain interaction and its role in interchain transfer [82]. They showed that the dopants mediate the largest interchain transfer of about 0.3-0.1 eV with five to seven carbon atoms in another chain that is in contact with a common dopant column. The interchain transfer via dopants has little effect on interchain states but yields a modification of the orbital energy spectrum. 

It is well known that in an ideal one-dimensional conductor the transverse orbital motion is restricted, thus the carriers cannot make circular motion in the presence of a magnetic field. Hence, one could hardly expect any MC in an ideal one-dimensional condnctor. However, in the presence of any finite interchain transfer integral, as in several q-lD conductors, the MC can be used as a powerful tool to investigate the intrachain versus interchain transport. Nevertheless, the fine features in anisotropic MC can be made inconspicuous in the presence of disorder. 

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