Physical Properties of the Phenylenes

As a novel class of hydrocarbons, the most important aspect of the phenylenes lies in their physical properties. The following sections will compare (to the extent that it is possible) structural, spectroscopic, and calculated aspects of the known 19 phenylenes. 

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The following account will describe progress in the synthesis and the chemical and physical properties of the phenylenes, in that order. It is written with the aim of placing all presently known members of this class of hydrocarbons, including 1, on a comparative footing [45]. 

As in the case of nylons, the flexibility of PUs is increased as the number of methylene groups is increased, and the rigidity is related to the number of stiffening groups, such as phenylene groups in the chain. As the number of methylene units increases (Table 14.6), the Tm decreases. The Tm generally increases as the flexible units are replaced by nonflexible units, such as phen-ylenes and piperazines. Thermal and physical properties of aliphatic PUs are shown in Table 14.7. 

From the same nitrone, or glyoxal-bis(>V-phenyl)-nitrone and m- or p-phenylene-bismaleimide, polymers, 88-91 are obtained.94 Some physical properties of these polymers are summarized in Table VII. 

H. B. Ouada, and H. Maaref. The effect of synthesis procedure on physical properties of poly(p-phenylene vinylene) derivatives. Eur. Polym. J., 37(4) 683-690, April 2001. 

Poly(p-phenylene sulfide), PPS, is the only commericially available processible precursor to a conducting polymer complex. Gas phase doping of PPS films with ASF5 leads to substantial chemical and physical alteration of the polymer and a substantial loss of the mechanical properties of the parent polymer. In this section we will describe a recently discovered method which allows the retention of processibility in the PPS system,... 

Another class of polymer that has received attention is based on PPP, e,g, poly(l,3-phenylene), poly(thio-l,4-phenylene) (11 poly(p-phenylene sulfide), PPS), etc A major advantage of PPP and PPS is that the undoped polymers are solution- and melt-processable. PPS is also available commercially. The physical properties of these polymers, undoped and doped, have been interpreted in terms of the bipolar on model. The validity of this approach has been questioned by chemical analysis, which has shown that these materials are complex mixtures of dissimilar oligomers rather... 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Poly(p-pheny lene)s, PPPs, constitute the prototype of rigid-rod polymers and are currently being intensively investigated [1]. The key role of PPPs follows from their conceptually simple and appealing molecular structure, from their chemical stability, and from their superior physical properties [2], In turn, this is the result of important advances made in aromatic chemistry over the last few years. The following section gives an overview of the most common methods to generate poly(p-phenylene)s via different synthetic approaches. 

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