Polyparaphenylene

The crystal structures of several doped species of Li have been determined by diffraction methods. While uncertainty shrouds the structure of lithium-doped PAc, it has been shown that (probably because of the small size of the Li ion) its accommodation in the polyparaphenylene (PPP) lattice occurs with very little modification to the position of the polymer chains. The Li ions occupy sites on the monoclinic (nearly orthorhombic) a and b axes, but although they thereby experience a channel-like environment, the walls of the channels are rhombic rather than tetragonal. 

Lattice simulations in Ref. 106 include structures of PPP doped with Li, K, and AsF 5 ions, which led to fully relaxed structures with unit-cell parameters that were reasonably close to experiment. Because of the simplicity of its unit cell, the Li-doped species was selected for a defective-lattice-type simulation.  

FIGURE 5.16. Response of host and dopant sublattices to various displacements z(Li) of a Li ion (labeled Li ) from its perfect-lattice site in Li-doped polyparaphenylene. Dopant ions are aligned between two PPP chains. (From Ref 107 by permission of the publishers.) 

In PPP dopant ions and appear to be more firmly held in their sites than 

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In 1979, the formation of conductive polypyrrole films by the electrochemical oxidation of pyrrole was reported for the first time This work has stimulated intense and fruitful research in the field of organic conducting polymers. Further important conductive polymers are polythiophene, polyaniline and polyparaphenylene. The development and technological aspects of this expanding research area is covered... 

Table 5.3 Examples of electronically conducting polymers, y is the level of electrochemical doping and k is the maximum electrical conductivity. Except for poly acetylene and polyparaphenylene, only p-doping is considered... 

Fig. 3. Structural diagrams for polyparaphenylene showing the non-degenerate benzenoid (a) and quinoid (b) configurations and (c) a polaron defect.

Leninivin, C. 2003. Elaboration et validation de derives polyparaphenylene sub-stitu suHonfe comme electrolyte solide pour piles a combustible a membrane hangeuse de protons. Ph.D. Dissertation, Poitiers University, France. 

Solitons are considered to be important defect states in these conjugated polymers (see Fig. 6.48). It has however been shown that correlation energy is the more important factor in giving rise to the energy gap in (CH) (Soos Ramasesha, 1983). Other polymers related to polyacetylene are polythiophene, polypyrrole, poly-phenylenesulphide, and polyparaphenylene (Section 3.3). Extensive measurements on doped polyacetylenes have been reported in the last five years and these materials, unlike other conducting polymers such as (SN), seem to have good technological potential. 

The application of Langmuir-Blodgett films as rectifiers and/or switches have been also proposed. Peterson [106] investigated two semiconductors polyparaphenylene 178 and polyphenylenevinylene 179 with these purposes in mind. These systems with the chain lengths of at least 20 units could also be used as photovoltaic devices since their electroluminescence should be readily detectable. The doping of such materials may be necessary but at present it is not clear whether they will form Langmuir-Blodgett films when doped. 

The exact relative locations of the lowest excited Bu and Ag states are difficult to predict on a theoretical basis. Indeed, they sensitively depend on the interplay between electron correlation effects and bond-length alternation effects, as shown for instance by Soos and his co-workers23. Strong effective bond alternations favour the 1BU state as the S, state this is the case in polyparaphenylene and PPV due to the presence of phenylene rings. The effective bond alternation is much weaker in polyacetylene while it is intermediate in polythiophene where the 2Ag state is found to lie slightly above the 1BU state. 

Endo M, Kim C, Hiraoka T, Karaki T, Matthews MJ, Brown SDM, Dresselhaus MS. Li storage behavior in polyparaphenylene (PPP)-based disordered carbon as a negative electrode for Li ion batteries, Mol Cryst Liq Cryst 1998 310 353-358. 

The conjugated systems in Fig. 2 have inversion and e-h symmetry. The acenes are the prototypical systems of molecular exciton theory[23]. The photophysics of stilbene and polyparaphenylene vinylene (PPV) have been extensively studied [14], separately at first and together since the preparation [24] of light-emitting diodes based on PPV. Pyrene and perylene appear in many contexts, while the polydiacet-... 

The synthesis and characterization of polyacetylene (PA) provided new incentive for understanding 7r-electronic spectra, electron-phonon interactions and electronic correlations[l, 2, 14]. The electrical conductivity of chemically doped PA rivals that of metals. Families in Fig. 2 such as polydiacetylenes (PDAs), poly thiophenes (PTs), cr-conjugated polysilane (PSs) and polyparaphenylene vinylene (PPVs), among... 

Ye J.H., Chen Y.Z., Tian Z.W. (1987) Electrochemical preparation of a polyparaphenylene film and a polyparaphenylene/polyacrylamine functional. 

The structure described above for PA is in fact typical of most nonsubstituted undoped CPs studied to date. Among the more extensively studied CPs, polyparaphenylene (PPP), polythiophene (PTh), and polyphenyl-... 

Another polymer composite that is of interest is the more complex system SbCls-doped polyparaphenylene/polyparaphenylene sulphide (PPP/PPS) sintered materials (Rueda etal, 1988). 

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