POLY ACETYLENE P Ac

Fig. 1-3 Structures of three other common CP s a) Poly(acetylene) (P(Ac)) b) Poly(para-phenylene) and c) Poly(para-phenylene-vinylene).

For poly (pyrrole), positively charged polarons and bipolarons have already been illustrated above, (Fig. 2-71. Negatively charged polarons and bipolarons can be visualized which are analogous to those of poly(p-phenylene), but in practice they do not exist, as poly(pyrrole) cannot be n-doped stably. For trans-poly(acetylene) (P(Ac)) (Fig. 2-13 ). one may have a neutral soliton and "antisoliton" possessing spin (a), and spinless positive and negative solitons (b) two adjacent, positive solitons would be the equivalent of a bipolaron, which for reasons cited earlier degenerates... 

CPs have been investigated for a very wide variety of battery applications, although mostly for secondary (rechargeable) batteries. They have been used as the anode as well as the cathode material, although cathode materials in Li secondary batteries have overwhelmingly been the main focus of interest. Applications have included all-CP (anode/cathode) batteries [685], lead-acid batteries [686], Zn batteries [687] and others. Although poly(aniline) (P(ANi)) and poly(pyrrole) (P(Py)) have overwhelmingly been the primary focus of interest, other common CPs studied have included poly(p-phenylene) (P(PP)), poly (acetylene) (P(Ac)), poly (thiophene) (P(T)). 

Naishadham [475] used the cavity perturbation technique to study the overall microwave characteristics, including EMI-SE, of the CPs poly(acetylene) (P(Ac)) and poly(p-phenylene-benzobisthiazole) (P(BT)), at 8.9 and 9.89 GHz, and continuously in the 2-20 GHz frequency region. Figs. 19-la.b.c summarize some of his results. 

Some of the first third order NLO studies of CPs were carried out on the poly(di-acetylenes) (P(DiAc)). One of the first such studies, on P(DiAc)-toluene sulfonate (PTS) single crystals, carried out by Sauteret et al. [502], revealed third order bulk NLO susceptibilities x fzzzz) polymer chain axis) of 1.6 X 10 ° esu at 2.62 pm and 8.5 X 10 ° esu at 1.89 pm. These values have as yet been exceeded only by one study, that of Drury on oriented Durham P(Ac) [503], in which a value for x zzzz> (Z= polymer chain axis) of 10 esu at 1.9 pm. However, this value of the susceptibility was inferred from THG data somewhat indirectly. Dennis et al. [504] reported off-resonant x xyyx values of 7 X 10 esu for solutions of various P(DiAc), extrapolated to pure substance and determined via DFWM at 532 nm. 

Substituted P(Ac)s may be synthesized using a wide variety of methods, primarily condensation polymerizations. Fig. 13-5 shows a sampling of these. Poly(phenyl acetylene) (P(PhAc)), a typical substituted P(Ac), is soluble in its undoped state in common organic solvents [563]. 

Poly(acetylene) probably comprises one of the most studied CPs for PV, heterojunction, rectification/Schottky barrier and related applications [959-961, 963-969, 971-976, 978]. One of the reasons for this is of course P(Ac) s lower bandgap, ca. 1.5 eV, which more closely matches the solar spectrum than, say, P(Py) (ca. 2.2 eV). 

---