Oxidative coupling polyphenylene oxides

Polyethers are obtained from three different classes of monomers, namely, carbonyl compounds, cyclic ethers, and phenols. They are manufactured by a variety of polymerization processes, such as polymerization (polyacetal), ring-opening polymerization (polyethylene oxide, polyprophylene oxide, and epoxy resins), oxidative coupling (Polyphenylene oxide), and polycondensation (polysulfone). 

Methylene Chloride Fractionation of Cross-Coupled 1. 2 and 7. A sample of the block polymer (above 0.50g) was dissolved in 10 mL of methylene chloride. The soluton was stored at 2 C for 2 days. A polymer methylene chloride complex precipitate formed which was removed by filtration at 2aC. The precipitate was then heated at 50 to drive off the methylene chloride. The dried polymer weighed 0.43g and contained (based on IR analysis) 58% by weight of poly(phenylene oxide) and 42% by weight of polystyrene. Analysis of the filtrate after evaporation of the methylene chloride established the presence of a residue containing 17% polyphenylene oxide and 83% polystyrene. On the basis of these results, at least 72% of the initial polystyrene charged to the reaotion medium was calculated as having been incorporated into an acyl-coupled polyphenylene oxide-polystyrene block polymer. 

COUPLING (Chemical). Reactions for the formation of chemical compounds usually by establishing a valence bond between a carbon atom and a nitrogen atom. Phenols and several other organic substances are also said "to couple. Polyphenylene oxides, thermoplastic materials, are produced by means of oxidative-coupling technology. 

White, D.M., Quinone-coupled Polyphenylene Oxides, US 4234706, 1980. (General Electric Co.)... 

When chloroform or methanol is used as the solvent for the oxidation of phenols, other products, originating from coupling of aryloxy radicals, e.g., polyphenylene ethers and/or diphenoquinones, are also formed. ... 

For many years there has been a demand for rigid plastics materials which could withstand temperatures of 250°C and at the same time have good oxidation and water resistance coupled with ease of processability and reasonable cost. Such a demand led in the late 1960s to the small-scale production of a number of polymers which could be considered as being intermediate between polyphenylene, Figure 23.24, and the commercial phenolic resins. 

Propylene oxide is one of the raw materials used to manufacture rubbery and crystalline polyepoxides. R. J. Herold and R. A. Livigni describe propylene oxide polymerization with hexacyanometalate salt complexes as catalyst. Polyphenylene oxide is made by copper catalyzed oxidative coupling of 2,6-dimethylphenol. G. D. Cooper, J. G. Bennett, and A. Factor discuss the preparation of copolymers of PPO by oxidative coupling of dimethylphenol with methylphenylphenol and with diphenylphenol. 

Touring the last decade, catalyzed oxidative coupling has gained wide-spread interest as a novel and general polymerization method. Various polymer systems of scientific and commercial interest have been prepared by this novel technique. Such polymer systems include polyphenylene oxides) (9, 13, 25), of which poly(2,6-dimethylphenylene oxide) (PPO) is produced commercially polyphenylenes (21) poly-... 

Crown ether-functionalized polyphenylenes are a class of electroactive polymers obtained by electropolymerization (anodic coupling) of (di)benzo- or (bi)naphthalene-crown ethers <1998CCR1211, 1998PAC1253>. Tricyclic triphenyl-ene derivatives, such as 78, can be electrogenerated from benzo-15-crown-5 <1989NJC131> and benzo-18-crown-6 <1992JEC399>. Similarly, the anodic oxidation of dibenzo-crown ethers has produced poly(dibenzo-crown ethers), best represented by 79, where triphenylene moieties are presumably two-dimensionally linked via polyether bridges. 

The anodic oxidation of benzene produces a mixture of polyphenylene compounds. This oligomerization can be performed in acetonitrile [21] or in liquid sulfur dioxide [22]. Mixed coupling between naphthalene and alkyl benzenes has also been demonstrated (Table 1, numbers 12-16). The relative yield of mixed coupling products increases with the basicity of the alkyl benzene with mesitylene 19%, with tetramethylbenzene 42%, and with pentamethylbenzene 64% of mixed coupling products are obtained. This suggests an electrophilic reaction between naphthalene cation radicals and alkylbenzenes. The mixed coupling reaction of phenanthrene with anisole has been studied kinetically. The results indicate that initially a complex PA is formed between the phenanthrene radical cation and anisole, followed by an electron transfer from the complex. The resulting PA" -anisole complex then decomposes to the product [23]. 

The Bjorklund works [169] lead us to develop a synthesis route in which the polypyrrole grows in the insulating matrix. Different solutions (PVC, polycarbonate, polyphenylene oxide,. ..) or emulsions (PTFE) of insulating polymer have been tested. In the case of PTFE-polypyrrole blend we used a classical oxidising coupling process by FeCl3 [104,127]. Comparative experiments have been performed on granular materials obtained by polypyrrole powder dispersion in an elastomer or an epoxyde resin [127]. 

The halogen groups can be incorporated directly in the backbone of the PPE. Consequently, tribro-mophenols have been condensed to get brominated polyphenylene oxide [72]. Obviously, the mechanism of polymer formation is different from that of oxidative coupling. The condensation takes place in the presence of NaOH, initially below room temperature. After condensation, a decolorization treatment is necessary. Hydrazine is used for decolorization. 

Oxidative coupling n. A process defined as a reaction of oxygen with active hydrogen atoms from different molecules, producing water and a dimerized molecule. If the hydrogen-yielding substance has two active hydrogen atoms polymerization results. This process is used in the polymerization of phenols, particular polyphenylene oxide. 

Substituted phenols undergo a variety of oxidative transformations in the presence of copper compounds [15, 117-119]. The nature of both phenol and ligands and the reaction conditions strongly affect the reaction selectivity. Hay and coworkers discovered the oxidative C—O coupling of 2,6-dimethylphenol to polyphenylene ether, an important industrial polymer, in the presence of a homogeneous Cu(I) catalyst and amines [117a]. The presence of large substituents (j-Pr or r-Bu) at ortho positions of phenol and elevated reaction temperature shift the oxidation... 

Some measurements of this property have been made in a range of electrically conducting polymers. These include epoxy resin/polyaniline-dodecylbenzene sulfonic acid blends [38], polystyrene-black polyphenylene oxide copolymers [38], semiconductor-based polypyrroles [33], titanocene polyesters [40], boron-containing polyvinyl alcohol [41], copper-filled epoxy resin [42], polyethylidene dioxy thiophene-polystyrene sulfonate, polyvinyl chloride, polyethylene oxide [43], polycarbonate/acrylonitrile-butadiene-styrene composites [44], polyethylene oxide complexes with sodium lanthanum tetra-fluoride [45], chlorine-substituted polyaniline [46], polyvinyl pyrolidine-polyvinyl alcohol coupled with potassium bromate tetrafluoromethane sulfonamide [47], doped polystyrene block polyethylene [38, 39], polypyrrole [48], polyaniline-polyamide composites [49], and polydimethyl siloxane-polypyrrole composites [50]. 

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