Polyparaphenylene PPP

Some heteroatom-substituted derivatives are known. Pyridines and quinolines have been pol)nnerized. An example, synthesized by step- wth polymerization, i poly(p-phenylene-co-2,5-pyrazine) shown in figure 18.  

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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 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-... 

By contrast, the ECP must have conjugated rigid-rod macromolecules. Several such polymers show high electrical conductivity (usually after doping), viz. polyacetylene (PAc), polyaniline (PANI), polypyrrole (PPy), polyparaphenylenes (PPP), or poly-3-octyl thiophene (POT). The resins are expensive, difficult to process, brittle and affected by ambient moisture, thus blending is desirable. For uniaxially stretched fibers the percolation threshold is 1.8 vol%, hence low concentration of ECP (usually 5-6 vol%) provides sufficient phase co-continuity to ascertain conductivity similar to that of copper wires (see Table 1.79). 

Finally an LDA calculation was also performed for a polyparaphenylene (PPP) helix.100 This conducting polymer (if doped) is quite interesting for its applications in light emitting diodes101 (especially because it emits blue light102), in field-effect transistors103 and in non-linear optical devices.104... 

For polyacetylene (PA) and polyparaphenylene (PPP) several investigations with cw-NMR have been reported [20-24]. Concerning this method, an improvement on how to estimate more accurately the second moment M2 has been proposed [25]. 

BT), they also act as models of the conjugated organic polymers polyparaphenylene (PPP) and polythiophene (PT), respectively. As is discussed in detail elsewhere [96], the results for the electronic excited states of the cation and anion of BP can be used for interpreting the polaron states in doped PPP. The main features of the spectra are reviewed briefly below. 

Irradiation (A>290nm) of a water suspension of polyparaphenylene (PPP) in the presence of triethylamine or diethylamine caused photocatalytic evolution of H2 from water [285]. The surface area of PPP determined by BET was 39.1 m /g. Although the photocatalytic activity of PPP was lower than that of a commercial monocrystal, such systems could eventually become promising photocatalysts for obtaining low-cost feedstock from water (Fig. 37). 

Phani et al. [99] reported the electrodeposition of polyparaphenylene (PPP) films on an indium-tin oxide glass and platinum electrode from a water-continuous SDS microemulsion containing benzene and concentrated sulfuric acid. It is difficult to obtain homogeneous coherent films of high molecular weight PPP via electrodeposition. The PPP films deposited... 

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. 

The insertion mechanism of the lithium ion into various kinds of carbons, when used as an anode in Li ion batteries has been extensively studied both experimentally and theoretically. However, the electrochemical insertion process is not yet fully understood. Polyparaphenylene (PPP)-based disordered carbon has a superior lithium storage capacity when used as an anode in the Li ion battery, and thus attracts much attention. In order to investigate the insertion mechanism of lithium into this material, the uptake and release processes of lithium were monitored by in situ Raman spectroscopy [90]. It was found that the band intensities of the characteristic peaks of disordered carbon decrease upon the discharging process and increase with the charging process, with quite good reversibility. Moreover, the frequency of the band related to the intraring C-C stretching mode of PPP at 1605 cm also... 

The deep and detailed work performed by different groups on the many PPV derivatives is only a part of the huge amount of other structures which were investigated with the aim of reaching valuable performances of polymeric LEDs. As the double bonds in PPV are reactive chemical functions which can be oxidised, the polyparaphenylene (PPP) structures were intensively investigated with the aim of obtaining more robust materials. 

Latonen et al. [1083] prepared a copolymer of 3-octylthiophene and paraphenylene. The recorded in situ infrared spectra showed bands previously found with pure polyparaphenylene (PPP) and POT. A copolymer of 3,4-i ,3, 4 -d dithienothiophene and aniline was studied by Mirzynska et al. [1084] using the rotating ring-disk electrode method. 

Complexation of metals to preformed polymers is a useful methodology for the synthesis of polymers incorporating metals into their backbones or sidechains. In 1984 the complexation of a molybdenum tricarbonyl complex to approximately 25% of the arenes in polyparaphenylene (PPP), was reported. This polymer displayed shifts in its IR spectrum similar to that of potassium-doped PPP. 

The prototypes of a large class of polyaromatic molecules that have been found to possess relevant electrical and/or optical properties are polyparaphenylene (PPP) and its oligomers (PP ), polyparaphenylenevinylene (PPV) and its oligomers (PV ), and the series of rylenes (Ry ). In the class of polyheteroaromatics, we consider oligopyrroles (Py ) and polypyrrole (PPy), oligothio-phenes (Th ) and poly thiophene (PTh), and some derivatives. 

Oligoparaphenylene (PP ) and polyparaphenylene (PPP) and many derivatives have been synthesized [219-222], but, after a strong show of interest during the early stages of this research, many turned to other classes of polyconjugated materials. 

Fig. 30.2 Chemical composition of various paraphenylene systems, (a) Parahexaphenyl (PHP) (b) polyparaphenylene (PPP) (c) paraphenylene-type ladder polymer (LPPP) and (d) a copolymer of PPP and LPPP (CoLPPP). The Y substituent of the material LPPPs is either a hydrogen atom or a methyl group (m-LPPP).

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