Poly p-Phenylene Sulfide

Synthetic routes to poly(p-phenylene sulfide) have been reviewed by Cleary71. The route used commercially is the polycondensation of 1,4-dichlorobenzene with sodium sulfide, typically carried out in a polar organic solvent, such as JV-methyl pyrrolidone at temperatures in the range 200 to 300 °C  

This reaction is reported to be much more difficult to perform than it appears. According to Rajan et al. 72) the mechanism is not typical of polycondensations, since appreciable amounts of high polymer are present at low conversions and unreacted monomer is found at high conversions. Numerous other synthetic routes have been described. According to Cleary 71) the only other process which has been unequivocally demonstrated to give the required polymer is the self condensation of alkali metal salts of 4-halothiophenols, as described by Lenz et al. 73). 

Although succesful, this reaction does not lead to polymers of sufficiently high molecular weight to be useful commercially. 

The literature on conductivity in poly(p-phenylene sulfide) is confused. According to Shacklette et al.74) heavy doping with AsF5 causes reduction of the polymer with the formation of fused benzothiophene structures which are responsible for conjugation. This would more properly place poly(p-phenylene sulfide) in the category of precursor polymers, discussed later. On the other hand, Friend and Giles 75) proposed an intrinsic conduction mechanism, based on optical measurements and Tsukamoto et al. 76) have presented XPS and 13C NMR measurements to support this view. 

Poly(p-phenylene oxide) is also a processible polymer, but its treatment with AsF5 leads only to rather poor conductivity77). The synthesis of poly(p-phenylene selenide) has been described by Jen et al. 78) and by Sandman et al. 79) but the polymer does not conduct even on prolonged exposure to AsF5. 

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Poly(p-phenylene sulfide ketone), 23 709 Poly(p-phenylene terephthalamide),... 

RS+ electrophiles that are electrogenerated in a CH2CI2/BU4NCIO4 solution readily attack even less reactive triple bonds of terminal alkynes [123] and result, after further oxidation and hydrolysis, in a-oxo-thioesters (Scheme 33). Under acidic conditions, it is possible to direct the reaction to the formation of an oligomer, cyclohexa-1,4-phenylene sulfide, or a conductive poly(p-phenylene)sulfide [131,132]. 

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. 

Poly(-p-phenylene sulfide) is an electronic material with good prospects due to high thermostability up to 280 °C and has the possibility of changing the resistance up to 19 orders of magnitude with doping. 

Most conducting polymers, such as doped poly(acetylene), poly(p-pheny-lene), and poly(p-phenylene sulfide), are not stable in air. Their electrical conductivity degrades rapidly, apparently due to reaction with oxygen and/or water. Poly(pyrrole) by contrast appears to be stable in the doped conductive state. 

Arylated and alkylated poly(p-phenylene sulfide) derivatives have been synthesized by the method shown in Eq. (33). Sulfonium ion polymers, such as 217, have potential applications as electronic components and lithographic materials [122]. 

Electrochemical doping is reversible and thus polymers which can be successfully cycled between two dopant levels can serve as rechargeable electrodes. Only polyacetylene, poly(p-phenylene) and poly(p-phenylene sulfide) are both oxidizable and reducible. Other conducting polymers can only be either p- or n-doped. 

We report the first syntheses of the selenium and tellurium analogs of the thermoplastic poly-p-phenylene sulfide (PPS), i.e., PPSe and PPTe, by reaction of p-dihalobenzenes with new alkali chalcogenide reagents under conditions significantly milder than those reported for PPS. The chemical, thermal, structural, and electrical properties of PPSe and PPTe are compared to those of PPS. While PPSe exhibits good thermal stability,... 

Anodic oxidation of diaryl disulfides results in polymerization [473, 474]. Thus oxidation of diphenyl disulfide 187, R=Ph, in the presence of trifluoro-acetic acid gave poly(p-phenylene sulfide) 209a. 

The oxidative polymerization of diphenyl disulfides or of thiophenal with quinones at room temperature has been reported to produce pure poly(p-phenylene sulfides) [37cJ. This will be described in more detail in Section 4. 

Poly(p-phenylene sulfide) was first reported in 1897 by Genvresse [92] who reported an insoluble resin prepared by the reaction of benzene with sulfur in the presence of aluminum ehloride. A variety of other procedures were reported to yield similar resins. Macallum [93] in 1948 reported a novel procedure that yielded an improved resin. Lenz and co-workers [94-96] modified the procedure and Edmonds and Hill [97] of the Phillips Petroleum Co. developed a commercially successful process. The material is now marketed under the trade name Ryton [98]. The crystallinity of the polymer has recently been reported [99-101]. 

Diphenyldisulfide can also be polymerized to poly(p-phenylene sulfide)s using Lewis acids such as SbCL at room temperature [111c]. However, these resins may be slightly contaminated by residual metal catalyst impurities. 

Fahey, D. R. and J. F. Geibel, Poly(p-phenylene sulfide) (Synthesis by p-Dichlorobenzene and Sodium Sulfide), pp. 6506-6515 in Polymeric Materials Encyclopedia, J. C. Salamone, ed., CRC Press, Boca Raton, FL, 1996. 

M. Wejchan-Judek and B. Perkowska. Curing of poly(p-phenylene sulfide). Polym. Degrad. StabiL, 38(3) 261-264, 1992. 

Y. Cohen and Z. Aizenshtat. Isothermal flnidized-bed studies on the kinetics and pyro-products of Unear and branched poly(p-phenylene sulfide) and proposed mechanisms. J. Anal. Appl. Pyrolysis, 27(2) 131-143, December 1993. 

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