Self-localized excitations

Thble I. Self-localized Excitations and Chemical Terminologies 

Self-localized excitation Chemical term Charge Spin 

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Self-localized excitations and corresponding chemical terminologies are listed in Table 4-2. Schematic structures of the self-localized excitations in poly(p-phenylene) and tranj-polyacetylene are depicted in Figure 4-3. In these illustrations, the charge and spin are localized on one carbon atom. In real polymers, however, they are considered to be localized over several repeating units with geometric changes. 

Table 4-2. Self-localized excitations and chemical terminologies.

Figure 4-3. Schematic structures of self-localized excitations in poly( p-phenylene) and trans-po y-acetylene. (a) Positive polaron (b) negative polaron (c) positive bipolaron (d) negative bipolaron (e) positive polaron (f) negative polaron (g) neutral soliton (h) positive soliton (i) negative soli-ton . D, donor A, acceptor -I-, positive charge negative charge , unpaired electron.

The Raman spectra of doped states of polyaniline [99], poly(/ -phenylenevinylene) [75, 100-102], and polythiophene [72, 73] have been also analyzed on the basis of the data of charged oligomers (charged oligomer approach). The detected self-localized excitations are summarized in Table 4-5. Some important conclusions can be drawn from these Raman studies. 

Table 4-5. Types of self-localized excitations detected by Raman spectroscopy.

Fig. 5. Schematic structures of self-localized excitations in polythiophene (a) a positive polaron, (b) a positive bipolaron, and (c) two positive polarons.

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