P-Polyphenylene

Since the thermal degradation in phenylated polyphenyls of the type XXa is caused by the loss of pendant phenyl groups, and since the reported (4, 7, 9, 10, 11, 14, 15) properties of p-polyphenylenes are quite different from those of XXa, the synthesis of an unphenylated polyphenylene by this pathway was of considerable significance. Only a few results employing this reaction have thus far been obtained. [The p-poly-phenylenes reported are black or brown, insoluble, crystalline materials of lower thermal stability than XXa.]... 

Hopefully, this type of synthesis will provide a p-polyphenylene of unquestionable structure so that its physical properties might be studied. 

Linear p-polyphenylene is thermally stable and crystalline, but brittle, insoluble and infusible. Therefore there has been considerable effort to insert flexible links such as —O—, —CO—, —NH—, O—CO—, —O—CO—O, N2, —S— or S02 without loss of thermal stability. Poly-p-xylylene has a melting point of 400°C and its mechanical properties are good. It is, however, insoluble and cannot be thermoprocessed. If one or more... 

Likewise, we have synthesized another key core segment based on a p-polyphenylene conducting unit which fits the general electronic architectural requirements. Conversion of 2-aminobiphenyl to the corresponding iodide under Sandmeyer conditions followed by lithium halogen exchange and quenching with fluorenone afforded the alcohol 11. Acid treatment to close the spiro system followed by reaction with bromine... 

Triphenyl phosphate [115-86-6] C gH O P, is a colorless soHd, mp 48—49°C, usually produced in the form of flakes or shipped in heated vessels as a hquid. An early appHcation was as a flame retardant for cellulose acetate safety film. It is also used in cellulose nitrate, various coatings, triacetate film and sheet, and rigid urethane foam. It has been used as a flame-retardant additive for engineering thermoplastics such as polyphenylene oxide—high impact polystyrene and ABS—polycarbonate blends. 

A-Substituted polypyrazoles can also be obtained by using A-alkylhydrazines, and it should be noted that these polymers consist of a random mixture of head-to-head and head-to-tail structures. Other syntheses of polypyrazoles have been described in the literature. Thus polyphenylene pyrazoles (742) and (743) occurred when m- or p-diethynyl-benzene (DEB) reacted with 1,3-dipoles such as sydnones or bis(nitrilimines) (Scheme 64). 

The successful development of polyfethylene terephthalate) fibres such as Dacron and Terylene stimulated extensive research into other polymers containing p-phenylene groups in the main chain. This led to not only the now well-established polycarbonates (see Chapter 20) but also to a wide range of other materials. These include the aromatic polyamides (already considered in Chapter 18), the polyphenylene ethers, the polyphenylene sulphides, the polysulphones and a range of linear aromatic polyesters. 

Although the first two materials discussed in this chapter, the polyphenylenes and poly-p-xylylenes, have remained in the exotic category, most of the other materials have become important engineering materials. In many cases the basic patents have recently expired, leading to several manufacturers now producing a polymer where a few years ago there was only one supplier. Whilst such competition has led in some cases to overcapacity, it has also led to the introduction of new improved variants and materials more able to compete with older established plastics materials. 

Several substituted linear polyphenylenes have also been prepared but none appear to have the resistance to thermal decomposition shown by the simple poly-p-phenylene. 

Newer fabrics, not in common use but in development, test, and field trials, are described for higher temperature applications by Reference [50]. Application to 400°F—2100°F are potentially available using ceramic fibers Nextel 312 , laminated membrane of expanded PTFE on a substrate, polyimid fiber P-84, Ryton polyphenylene sulfide, and woven fiberglass. The heat and acid resistance of these new materials... 

Another group of reactions can be classified as intermolecular dehalogenations or dehydrohalogenations, based on Wurtz-, Fittig-, Ullmann-, Grignard-, or Friedel-Crafts reactions. Thus, polyphenylenes may be obtained by polycondensations of p-dichlorobenzene in the presence of Na/K alloy83-85. ... 

Wessjohann LA, Ruijter E (2005) Strategies for Total and Diversity-Oriented Synthesis of Natural Product(-Like) Macrocycles. 243 137-184 Wiesler U-M,Weil T, Mullen K (2001) Nanosized Polyphenylene Dendrimers.212 1-40 Williams P, see Chhabra SR (2005) 240 279-315... 

In 1966, Cadotte developed a method for casting mlcroporous support film from polysulfone, polycarbonate, and polyphenylene oxide plastics ( ). Of these, polysulfone (Union Carbide Corporation, Udel P-3500) proved to have the best combination of compaction resistance and surface microporosity. Use of the mlcroporous sheet as a support for ultrathin cellulose acetate membranes produced fluxes of 10 to 15 gfd, an increase of about five-fold over that of the original mlcroporous asymmetric cellulose acetate support. Since that time, mlcroporous polysulfone has been widely adopted as the material of choice for the support film in composite membranes, while finding use itself in many ultrafiltration processes. 

Nemec H, Nienhuys H-K, Perzon E, Zhang F, Inganas O, Kuzel P, Sundstrom V (2009) Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy. Phys Rev B 79 245326... 

Ballard, D., Blacker, A.J., Woodley, J.M. and Taylor, S.C. (1994) Polyphenylenes from Biosynthetic cw-Dihydroxycyclohexadiene. n Plastics from microbes, edited by D.P.Mobley, pp. 139-168. Munchen Carl Hanser Verlag. 

In general, regularity in polymer structure and strong intermolecular forces favor high Tm values. Phenylene groups, such as those in polyphenylene, poly-p-phenylene oxide (PPO), and poly-p-phenylene sulfide (PPS), increase Tm values. 

Dealing with the same type of rigid-rod ionomers, Wallow and Novak recently prepared [44,45] a series of carboxy pendent polyphenylenes (XI). Using a Pd(o) water soluble catalyst, p-ordered polyphenylenes were prepared... 

RYTON Polyphenylene sulfide Physical, Chemical, Thermal, and Electrical Properties, TSM-266, Phillips Chemical Co., Bartlesville, Okla., Apr. 1981, p. 2. 

The coupling can be catalysed by the presence of Fe(III) or Co(ll) but is most efficiently induced by the dipyridyl complex of Ni(II) chloride, as described by Yamamoto et al.52). It is also efficiently promoted by l,4-dichoro-2-butene, as described by Taylor et al.53). The structures of these Yamamoto polyphenylenes are discussed in Sect. 3 at this point it is sufficient to note that they are yellow/brown infusible powders, apparently having a high degree of p-coupling but relatively short (10—12 rings) chain lengths. 

Fig. 14a-c. Crystal structures of a /ranr-polyacetylene, b cis-polyacetylene and c polyphenylene. Reproduced with permission a from Ref.6) p. 103, b and c from Ref. 2861... 

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