Benzene oxidative polymerization

Figure 4. Catalytic activity of the pyridine-Cu catalyst in DMSO-benzene solvent (a) and activity of the PSP-Cu catalyst in DMSO (b) (O) oxidative polymerization rate of XOH (A) rate constant of electron transfer step (ke) (0) rate constant of catalyst reoxidation step...

One of the earliest attempts to synthesize heat-resistant polymers was the oxidative polymerization of benzene to poly(p-phenylene) [IUPAC poly(l,4-phenylene)] (Eq. 2-227) [Jones... 

The catalytic activity of the metal complex on the oxidative reaction in solution is much influenced not only by the species and the structure of the complexes but also by the chemical environment around them. For instance, in the oxidative polymerization of phenols catalyzed by a Cu complex, the reaction rate varied about 102 times with changes in the composition of the solvent, and the highest rate was observed for polymerization in a benzene solvent162. Thus, we used the copolymer of styrene and 4-vinylpyridine(PSP) as the polymer ligand and studied the effect on the catalysis of the non-polar field formed by the polymer ligand163. ... 

Another mechanism has been proposed for the oxidative polymerization of benzene in HF/SbFs in the presence of an applied potential [312]. In this proposed mechanism, the coupling step occurs after protonation... 

Mara. Kamei and Osada [109 described a detailed study of the thermal decomposition of TNT. They examined the decomposition by differential thermal analysis, thermogravimetry, infra-red spectroscopy. HSR and mass spectrometry. One of their most important findings was that TNT produced free radicals already in the vicinity of the melting point, that is SO C. The substances which promote the decomposition of TNT are free radicals which are stable at room temperature. They are insoluble in benzene or chloroform and are partly oxidized polymeric substances. 

Phenols are oxidized by NaBiO3 to polyphenylene oxides, quinones, or cyclohexa-2,4-dienone derivatives, depending on the substituents and the reaction conditions [263]. For example, 2,6-xylenol is oxidized in AcOH to afford a mixture of cyclohexa-dienone and diphenoquinone derivatives (Scheme 14.123) [264] and is oxidatively polymerized in benzene under reflux to give poly(2,6-dimethyl-l,4-phenylene) ether (Scheme 14.124) [265]. Substituted anilines and a poly(phenylene oxide) are oxidatively depolymerized by NaBiO, to afford the corresponding anils [266]. Nal iO, oxidizes olefins to vicinal hydroxy acetates or diacetates in low to moderate yield [267]. Polycyclic aromatic hydrocarbons bearing a benzylic methylene group are converted to aromatic ketones in AcOH under reflux (Scheme 14.125) [268]. 

Poly(styryl)lithium (> 15,000) In benzene solution was reacted with excess ethylene oxide In the presence of N,N,N, N -tetramethyl-ethylenedlamlne (TMEDA, [TMEDA]/[Li] 3.2). After 12 days at 25-30 C, size exclusion chromatographic analyses Indicated no significant ethylene oxide polymerization. Hydroxyethylated polystyrene was recovered in essentially quantitative yleU. 

The polymer that results when benzene is reacted with the powerful oxidizers 02+ and C6F6+ is readily oxidized by AsF5 (13,14). (AsF5, although not capable of initiating the polymerization of benzene, can polymerize the more easily oxidized phenylene oligomers, including biphenyl). 

Coral-hke nanowires and nanowire networks of conducting PPy have been synthesized by chemical oxidation polymerization of pyrrole monomers in a dodecyl-benzene sulfonic acid (DBSA) aqueous solution with FeCla as oxidant and poly(vinyl-alcohol) (PVA) as... 

The synthesis of conjugated polymers is highly dependent on the effective carbon-carbon single bond generation between unsaturated carbons in aromatic molecules. Aromatic units in conjugated polymers can be benzene, aniline, pyrrole, thiophene, carbazole, naphthalenediimide, perylenediimide (PDI), or their derivatives, etc. Although monomers are various, their synthetic methods can be mainly classified into chemical and electrochemical polymerizations. Chemical polymerization includes chemical oxidative polymerization and metal-catalyzed coupling condensation. 

Scheme 13.1 Stoichiometry of the oxidative polymerization of benzene under Kovacic conditions.

The polymerization is thought to proceed via cationic processes. PPP prepared by this method essentially has a linear structure and DP of about 50 this DP is comparable to that of PPP prepared via Grignard coupling. Dehydro electrochemical oxidative polymerization of benzene has also been reported. ... 

DiMarco et al. [195] oxidatively polymerized yV-vinyl-thionaphthene-indole in methylene chloride at 1.2 V (versus SCE). Tetrabutylammonium perchlorate was added as the supporting electrolyte the monomer was used in concentrations greater than 5 x 10" M. Elemental analysis and mass spectroscopy results indicate that the polymer consists of four or more monomer units and that the benzene rings... 

In the 1960s, oxidative polymerization of benzene by CnCl2-AlCl3 was discovered (eq. 10) (226). Other oxidants such as AlCl3-Mn02, FeCl3, and M0CI5 were employed. These systems allowed the polymerization of varions monomers such as toluene, chlorobenzene, diphenyl, naphthalene, and phenanthrene (227). 

Three reaction mechanisms of C—C coupling in oxidative polymerization of benzenes have been reported (Fig. 9). The first step of each mechanism is one electron oxidation of a monomer to give a cation radical. The next step may be (i) conpling of two cation radicals (233,234), (ii) coupling of one cation radical with one neutral molecule (226,228), or (iii) coupling of one cation radical with many neutral molecules (stair-step mechanism) (235). 

For the oxidative polymerization of heterocyclic aromatics, two reaction mechanisms, similar to that of benzenes, have been proposed (Fig. 10). One is coupling of two cation radicals [(i) in Fig. 10] (240,241), and the other is coupling of one cation radical with one neutral molecule [(ii) in Fig. 10] (242,243). 

Methyl isobutyl ketone is a solvent used in insecticides, fungicides, electroplating solutions, leather finishing, and textile coatings. Faster condensation reaction rates are claimed in the polymerization of poly(ethylenetere-phthalate) when MIBK is added as a catalyst solvent. Cyclohexanone is used in paint removers, metal degreasing formulations, printing inks, and as an activator in oxidation reactions (e.g., benzene oxidation to give phenol). Cyclohexanone is a chemical intermediate in the manufacture of Nylon 6. 

It seems more likely that the reduction of the benzene oxidation potential (about 1 V in superacid media [106], which in any case results from a strong interaction of benzene with the proton, is due to the formation of a 7r-complex, more easily oxidizable than the single monomer [106]. This hypothesis is supported by the fact that the same fall in potential was observed when benzene was polymerized in SO2... 

By analogy with the electrochemical polymerization of 3-alkylthiophene and oxidative polymerization of benzene with aluminum chloride/copper(Il) chloride, the polymerization of 3-alkylthiophene with iron(III) chloride was assumed to proceed via a radical cation mechanism. This is a difficult problem which needs further studies. 

HydrosUylation was also applied to the preparation of thiophene-terminated dimethyl-siloxane macromonomer, which is used for the synthesis of thiophene-dimethylsiloxane graft copolymers by oxidative polymerization Polycarbosilanes have been prepared by hydrosUylation-polymerization of l,4-bis(ethenylmethylphenylsilyl)benzene with 1,4-bis(methylphenylsilyl)benzene in various ratios. ... 

In the framework of this research topic, PPy chains self-assembled in nanowires with a coral-like shape can be obtained by FeCb induced oxidative polymerization and dodecil-benzenic sulphonic acid (DBSA) dopant [106] oxidative polymerization is a widely used method for the attainment of polymeric nanostructures. For example, bundles of self-assembled PPy nanotubes have been fabricated by polymerization reaction with bis(2-ethylhexyl) sulfosuccinate reverse (water-in-oil) emulsions [107] and rods with enhanced electrical conductivity and thermal stability are reported to be formed via a self-assembly process of micelle obtained from a oxidative polymerization in the presence of p-toluensulfonic acid used as surfactant and doping agent [108, 109]. A further example of PPy nanotubes synthesized by oxidative polymerization in octane is reported in Fig. 1.7 [107]. 

The polyaniline nanofibers (PANI-NF) were synthesized by oxidative polymerization of aniline monomer at 0 °C in an ice bath using ammonium persulfate as the oxidant in the presence of surfactant. Aniline, ammonium persulfate, dodecyl benzene sulfonic acid, acrylmethylpropyl sulfonic acid, and camphorsulfonic acid are used as received from Sigma-Aldrich. Sulfonic acid-based surfactants as the dopant and ammonium persulfate as the oxidant were used in the present synthesis of polyaniline nanofibers (see flow charf in Fig. 8.17). Calculated quantities of aniline monomer (0.05 mol) were mixed with 50 mL of distilled water and stirred using magnetic stirrer for 10 min. Meanwhile, calculated quantities of surfactant (0.75 mol) and oxidant (0.05 mol) were dissolved separately in distilled water and stirred for 10 min in an ice bath. The surfactant solution was first added into the aniline monomer aqueous solution and then previously cooled oxidant solution dropwise, and the mixture was allowed to react for 15 h in an ice bath. 

---