1.4- Dichlorobenzene sodium sulfide reaction

The neat resin preparation for PPS is quite compHcated, despite the fact that the overall polymerization reaction appears to be simple. Several commercial PPS polymerization processes that feature some steps in common have been described (1,2). At least three different mechanisms have been pubUshed in an attempt to describe the basic reaction of a sodium sulfide equivalent and -dichlorobenzene these are S Ar (13,16,19), radical cation (20,21), and Buimett s (22) Sj l radical anion (23—25) mechanisms. The benzyne mechanism was ruled out (16) based on the observation that the para-substitution pattern of the monomer, -dichlorobenzene, is retained in the repeating unit of the polymer. Demonstration that the step-growth polymerization of sodium sulfide and /)-dichlorohenzene proceeds via the S Ar mechanism is fairly recent (1991) (26). Eurther complexity in the polymerization is the incorporation of comonomers that alter the polymer stmcture, thereby modifying the properties of the polymer. Additionally, post-polymerization treatments can be utilized, which modify the properties of the polymer. Preparation of the neat resin is an area of significant latitude and extreme importance for the end user. 

Dioxins, 1,4-oxathiins, and 1,4-dithiins have often been prepared by elimination reactions from saturated analogs as described in CHEC-II(1996) <1996CHEC-II(6)447>. Since then, a synthesis of tetramethyl l,4-dithiin-2,3,5,6-tetracarboxylate 241 has been reported in low yield (12%) by thermal decomposition of the 1,4,2,5-dithiadiazine system 240 in refluxing o-dichlorobenzene in the presence of DMAD <1997J(P1)1157>. Recently, 2,6-divinyl-l,4-dithiin 68 has been isolated from the reaction of l,4-bis(4-bromobut-2-ynyloxy)benzene with an excess of alumina-supported sodium sulfide. The formation of 68 has been presumed to take place via cyclic sulfide 242 <2003S849>. 

A commercial process for polyphenylene sulfide, (-( S-)x, was developed in 1967 by the reaction of para-dichlorobenzene and sodium sulfide in a polar solvent (1)- This polymer is very versatile. Selected grades can be used for extrusion and for production of a wide range of injection molding compounds. Typical properties of a 40% glass-reinforced compound are given in Table I. 

The above two methods as well as other methods of polymerization have been reviewed by Smith (7). We have discovered a new process for the preparation of a wide variety of polyarylene sulfides (8). For example, polyphenylene sulfide may be prepared by the reaction of p-dichlorobenzene and sodium sulfide in a polar solvent. 

The other process involves the reaction of dichlorobenzene and sodium sulfide (12) ... 

Macallum [93,110] reported a more convenient poly(phenylene sulfide) syntheses by the reaction of />-dichlorobenzene in a dry state using a mixture of sulfur and sodium carbonate at 300°-340 C. Macallum reported that if sodium sulfide were used in place of sodium carbonate and sulfur then a small amount of sulfur was still required to catalyze the reaction (Eq. 31). 

Aromatic polythioethers or polysulfides are closely related to polyethers in structure and properties. A typical aromatic polysulfide is poly(phenylene sulfide) (PPS) (20), which is used as electrical insulators and structural parts in the building of engines and vehicles. Poly(phenylene sulfide) is prepared by the condensation reaction between /7-dichlorobenzene and sodium sulfide ... 

Poly(phenylene sulfide) (PPS) is the thio analogue of poly(phenylene oxide) (PPO) [57]. The first commercial grades were introduced by Phillips Petroleum in 1968 under the trade name Ryton. Other manufacturers also have introduced PPS (e.g., Tedur by Bayer). The commercial process involves the reaction of p-dichlorobenzene with sodium sulfide in a polar solvent. 

It also forms by a reaction of dichlorobenzene with sodium sulfide. To date, the exact mechanism... 

Poly(thio-l,4-phenylene), also called poly(phenylene sulfide) or PPS, is produced by the reaction of 1,4-dichlorobenzene with sodium sulfide in A -methyl pyrrolidone ... 

It also forms by a reaction of dichlorobenzene with sodium sulfide [110]. To date, the exact mechanism of this polymerization, which is carried out commercially in A-methylpyrrolidone solution, has not been fully established. Recent evidence indicates that in this solvent, an ionic, step growth SNAr mechanism predominates [110] ... 

Polyphenylene sulfides (PPS), partially crystalline polymers, are produced by the reaction of p-dichlorobenzene and sodium sulfide. This polymer has metallic-like properties and responds well to reinforcement. PPS possesses good creep and good moisture resistance and a low coefficient of thermal expansion. 

Attempts to synthesize aromatic polysulfides by electrophilic substitution methods have failed to produce linear high molecular weight polymers. During the past three decades a systematic approach has been taken for the synthesis of aromatic polysulfides. The nucleophilic reaction of sodium sulfide with p-dichlorobenzene to give poly(phenylene sulfide) has been a successful process. The polymer produced by this method is abbreviated as PPS and has been commercialized by Philips Chemical Company under the trade name Ryton (reaction 24)... 

Edmonds and HiU discovered the first commercially viable process for the synthesis of PPS in 1967 in the laboratories of Phillips Petroleum Company. The patent [8] describing the Edmonds and HiU process was issued that year and effectively prevented others from entering the business until its expiration in 1984. The process involves the reaction of a polymerizable sidfur source derived from sodium sulfide and p-dichlorobenzene in a suitable polar organic compound at elevated temperature and pressure. N-methyl-2-pyrrolidone (NMP) is the preferred polar organic compound. The Edmonds and HUl process is stUl used commercially for some products manufectured by Chevron Phillips Chemical Company LP. The essential process steps in the Edmonds and HUl process are... 

Polyphenylene sulfide (PPS) is a relatively inexpensive material made by the reaction of sodium sulfide and dichlorobenzene. It... 

Poly(/ -phenylesulfide), PPS, (white powder, Tg 92 °C, mp 270-290 °C, 65% crystallinity) was the first melt-proccessible polymer to be doped with strong electron acceptors (e.g., ASF5) to yield highly conductive products [90]. The first laboratory synthesis of PPS was reported by Macallum [91] and involved the melt reaction of 1,4-dichlorobenzene, sulfur and sodium carbonate. A commercially product has been available as powder, film or fiber since 1973 from Phillips Petroleum under the trade name Ryton it is produced from 1,4-dichlorobenzene and sodium sulfide (high-pressure process) in a polar solvent (N-methylpyrrolidone) [92]. 

The high-temperature condensation of aromatic halides (diphenylsulfide, thian-threne, diphenyldisulfide, thiophenol and direct reactions of benzene with sulfur) in the presence of aluminium chloride was examined by Sergeyev et al. [98]. The reaction of 1,4-dichlorobenzene or 1,4-dibromobenzene with sodium sulfide at 195 °C in N-methylpyrrolidone (NMP) has been studied under normal atmospheric pressure, the kinetic of polymerization was found to be of second order. The same reaction in NMP was revised by Russian authors [99]. The polymerization of diphenyldisulfide produced PPS when stoichiometric amounts of diphenyldisulfide and antimoniumpentachloride were used in nitrobenzene at 20 °C. The S-S bond cleavage is catalyzed by the Lewis acid and the authors claim to have obtained an identic product compared with the commercial one with a molecular weight >1000 [100]. 

Nakayama et at. used thienyl-substituted 1,4-dithiins which are obtained from easily accessible diketosulfides for the preparation of a-oligothiophenes and isomers up to the heptamer [37b, 120]. The dithienyldiketosulfides 91-93 are prepared by the reaction of chloroaeetyl-substituted (oligo)thiophenes and sodium sulfide in almost quantitative yield and are further cyclized to the corresponding 1,4-dithiins 94-96 with L.R. in 60% yield. The extrusion of sulfur from the dithiin moiety via ylide intermediates is achieved by refluxing the dithiin in o-dichlorobenzene and results in a mixture of two possible isomers [Eq. (45)]. In the case of 2,6-di-(2 thienyl)-1,4-dithiin 94, a ratio of 13 1 of H-T3-H 3 and the 2,3 4, 2"-isomer 97 in 85% yield is obtained. The separation of the compounds by recrystallization turns out well since the a,/ -connected terthiophene is better soluble in hexane. Oxidation of the dithiin with nz-chloroperoxybenzoic add and extrusion of SO from the resulting sulfoxide in the presence of DMSO afford a mixture of H-T3-H 3 and the isomer 97 in a ratio of 22 1 and in a total yield of 90% [120]. 

A single electron transfer mechanism seems also to best explain the synthesis of poly(thio-l,4-phenylene) from 1,4-dichlorobenzene and sodium sulfide. The mechanism of the halogen displacement phase transfer-catalyzed polycondensation of 4-bromo-2,6-dimethylphenol occurs by a single electron transfer reaction which leads to a telechelic PPO containing one bromophenyloxy and one phenolic chain end of controllable molecular weight. 

The aliphatic thioethers (polysulfides) are unique among condensation polymers in being produced in an emulsion polymerization. The rank jr (Table 17.2, II.C) has an influence on the number of sulfur atoms in each polymer linkage. The tacky or liquid polymers are cast or applied as pastes in the case of sealants. The sulfur analog of poly(phenylene oxide) is poly(phenylene sulfide) (Table 17.2, II.C), which can be made by a condensation reaction between p-dichlorobenzene and sodium sulfide. The highly crystalline polymer is solvent resistant and has a low coefficient of friction. It can be injection molded at about 300°C and can also be used as a powder spray coating. 

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