Copper polymer oxidation catalyzed

Oxidative coupling polymerization provides great utility for the synthesis of high-performance polymers. Oxidative polymerization is also observed in vivo as important biosynthetic processes that, when catalyzed by metalloenzymes, proceed smoothly under an air atmosphere at room temperature. For example, lignin, which composes 30% of wood tissue, is produced by the oxidative polymerization of coniferyl alcohol catalyzed by laccase, an enzyme containing a copper complex as a reactive center. Tyrosine is an a-amino acid and is oxidatively polymerized by tyrosinase (Cu enzyme) to melanin, the black pigment in animals. These reactions proceed efficiently at room temperature in the presence of 02 by means of catalysis by metalloenzymes. Oxidative polymerization is observed in vivo as an important biosynthetic process that proceeds efficiently by oxidases. 

The main function of metal deactivators (MD) is to retard efficiently metal-catalyzed oxidation of polymers. Polymer contact with metals occur widely, for example, when certain fillers, reinforcements, and pigments are added to polymers, and, more importantly when polymers, such as polyolefins and PVC, are used as insulation materials for copper wires and power cables (copper is a pro-oxidant since it accelerates the decomposition of hydroperoxides to free radicals, which initiate polymer oxidation). The deactivators are normally poly functional chelating compounds with ligands containing atoms like N, O, S, and P (e.g., see Table 1, AOs 33 and 34) that can chelate with metals and decrease their catalytic activity. Depending on their chemical structures, many metal deactivators also function by other antioxidant mechanisms, e.g., AO 33 contains the hindered phenol moiety and would also function as CB-D antioxidants. 

Asymmetric induction by polymer-immobilized complexes is an important reaction in oxidation processes (this has already been demonstrated for the hydrogenation transformations described in Section 12.2.9). There are three different methods of synthesis of optically active compounds from optically inactive racemic mixtures spontaneous, biochemical and chemical. The chemical method is the most common. Immobilized metal complexes are the best models of asymmetric induction by enzymes. They produce large quantities of enantiomeric products from small quantities of chiral compounds. (Ascorbate oxidase is a copper-containing enzyme catalyzing aerobic oxidation of vitamin C. Its... 

Wet, chemical pretreatment of the polyetherimide substrates was affected via the Standard 2312 process. This scheme was comprised of a surface removal step, typically 0.5 pm is solubilized, polymer oxidation, and catalyzation and electroless metallization. The pretreatment sequence served to "normalize" the polymer surface and left the filler material, if any, unexposed. Either 1-2 pm of copper or -1 pm of nickel was electrolessly deposited. Following deposition of the initial metal layer, a 1 h heat treatment at 110°C was performed. Unless stated otherwise, air was the atmosphere during heat treatment. 

In polymers, oxidative degradation is catalyzed strongly by traces of metals that can undergo redox reaction. Most prominent is copper, but also solubilized iron, cobalt, nickel, chromium and manganese may contribute to degradation of the polymers. Apart from polymers, metal deactivators are used widely in lubricating oils. 

The oxidative coupling of 2,6-dimethylphenol to yield poly(phenylene oxide) represents 90—95% of the consumption of 2,6-dimethylphenol (68). The oxidation with air is catalyzed by a copper—amine complex. The poly(phenylene oxide) derived from 2,6-dimethylphenol is blended with other polymers, primarily high impact polystyrene, and the resulting alloy is widely used in housings for business machines, electronic equipment and in the manufacture of automobiles (see Polyethers, aromatic). A minor use of 2,6-dimethylphenol involves its oxidative coupling to... 

Figure 8. Lineweaver-Burk plots for oxidative coupling of DPP catalyzed by copper complexes of polymer ligand (I) with a =0.39 at 5 different temperatures. [CuCle]0 = 3.3mM N/Cu = 1 solvent 1,2-dichlorobenzene/methanol (13 2,...

Since the oxidative polymerization of phenols is the industrial process used to produce poly(phenyleneoxide)s (Scheme 4), the application of polymer catalysts may well be of interest. Furthermore, enzymic, oxidative polymerization of phenols is an important pathway in biosynthesis. For example, black pigment of animal kingdom "melanin" is the polymeric product of 2,6-dihydroxyindole which is the oxidative product of tyrosine, catalyzed by copper enzyme "tyrosinase". In plants "lignin" is the natural polymer of phenols, such as coniferyl alcohol 2 and sinapyl alcohol 3. Tyrosinase contains four Cu ions in cataly-tically active site which are considered to act cooperatively. These Cu ions are presumed to be surrounded by the non-polar apoprotein, and their reactivities in substitution and redox reactions are controlled by the environmental protein. 

The study of the molecular weight of the intermediate course is an effective method for the classification of polymerization as chain or stepwise reaction. In Figure 3, the molecular weight of the obtained polymer is plotted against the yield, for the oxidative polymerization of dimethylphenol with the copper catalyst and for the electro-oxidative polymerization. The molecular weight rises sharply in the last stage of the reaction for the copper-catalyzed polymerization. This behavior is explained by a stepwise growth mechanism. 

Copper-catalyzed oxidations of phenols by dioxygen have attracted considerable interest owing to their relevance to enzymic tyrosinases (which transform phenols into o-quinones equation 24) and laccases (which dimerize or polymerize diphenols),67 and owing to their importance for the synthesis of specialty polymers [poly(phenylene oxides)]599 and fine chemicals (p-benzoquinones, muconic acid). A wide variety of oxidative transformations of phenols can be accomplished in the presence of copper complexes, depending on the reaction conditions, the phenol substituents and the copper catalyst.56... 

Catechol melanin, a black pigment of plants, is a polymeric product formed by the oxidative polymerization of catechol. The formation route of catechol melanin (Eq. 5) is described as follows [33-37] At first, 3-(3, 4 -dihydroxyphe-nyl)-L-alanine (DOPA) is derived from tyrosine. It is oxidized to dopaquinone and forms dopachrome. 5,6-Dihydroxyindole is formed, accompanied by the elimination of C02. The oxidative coupling polymerization produces a melanin polymer whose primary structure contains 4,7-conjugated indole units, which exist as a three-dimensional irregular polymer similar to lignin. Multistep oxidation reactions and coupling reactions in the formation of catechol melanin are catalyzed by a copper enzyme such as tyrosinase. Tyrosinase is an oxidase con-... 

Many amine-copper complexes, as well as a few amine complexes of other metals, and certain metal oxides have since been shown to induce similar reactions (17, 18, 22, 23, 30). This chapter is concerned largely with the mechanism of oxidative polymerization of phenols to linear polyarylene ethers most of the work reported has dealt with the copper-amine catalyzed oxidation of 2,6-xylenol, which is the basis for the commercial production of the polymer marketed under the trade name PPO, but the principal features of the reaction are common to the oxidative polymerization of other 2,6-disubstituted phenols. 

Polyvinylidene fluoride (PVDF) is considerably less thermally stable than PTFE but much more stable than polyvinyl fluoride (PVF) or polychlorotrifluoroethylene (PCTFE). Certain inorganic compounds (silica, titanium dioxide, and antimony oxide) can catalyze its decomposition at temperatures above 375°C (707°F) [10], ETFE degradation is autocatalytic and similar to that of PVDF and is accompanied by the evolution of hydrogen fluoride (HF). Iron and transition metal salts can accelerate the degradation of ETFE by dehydrofluorination and oligomer formation [10], Copper salts have been found to stabilize the polymer [11], ETFE decomposes rapidly at temperatures above 380°C (716°F) [11],... 

Poly (oxy-2,6-dimethyl-1,4-phenylene) (poly (phen-ylene oxide), PPO) is widely used as a high-performance engineering plastic, since the polymer has excellent chemical and physical properties, e.g., a high Tg (ca. 210 °C) and mechanical toughness. PPO was first prepared from 2,6-dimethylphenol monomer using a copper/amine catalyst system.25 The HRP-catalyzed polymerization of 2,6-dimethylphenol gave the polymer consisting of exclusively oxy-l,4-phe-nylene units.26... 

Side reactions such as termination and transfer were investigated in the polymerizations of styrene,291 acrylates,292 and methacrylates.293 The occurrence of thermally initiated radical polymerizations was observed in the copper-catalyzed styrene polymerization, while the resulting polymer chain can be converted into the dormant polymer terminal via abstraction of halogens from the persistent metal radical in higher oxidation states.294... 

The ABA-type block copolymers B-86 to B-88 were synthesized via termination of telechelic living poly-(THF) with sodium 2-bromoisopropionate followed by the copper-catalyzed radical polymerizations.387 A similar method has also been utilized for the synthesis of 4-arm star block polymers (arm B-82), where the transformation is done with /3-bromoacyl chloride and the hydroxyl terminal of poly(THF).388 The BAB-type block copolymers where polystyrene is the midsegment were prepared by copper-catalyzed radical polymerization of styrene from bifunctional initiators, followed by the transformation of the halogen terminal into a cationic species with silver perchlorate the resulting cation was for living cationic polymerization of THF.389 A similar transformation with Ph2I+PF6- was carried out for halogen-capped polystyrene and poly(/>methoxystyrene), and the resultant cationic species subsequently initiated cationic polymerization of cyclohexene oxide to produce... 

B-90 and B-91, respectively.390 Another route coupled with cationic ring-opening polymerizations is accomplished for polymer B-92 with the use of a hydroxyl-functionalized initiator with a C—Br terminal, where the OH group initiates the cationic polymerizations of 1,3-dioxepane in the presence of triflic acid.329 Polyethylene oxide)-based block copolymers B-93 are obtained by living anionic polymerization of ethylene oxide and the subsequent transformation of the hydroxyl terminal into a reactive C—Br terminal with 2-bromopropionyl bromide, followed by the copper-catalyzed radical polymerization of styrene.391... 

Other multifunctional initiators include star polymers prepared from initiators via living radical or other living polymerizations. In particular, all of the star polymers via metal-catalyzed living polymerization, by definition, carry a halogen initiating site at the end of each arm, and thus they are potentially all initiators. Thus, star-block copolymers with three polyisobutylene-Mock-PMMA arms and four poly-(THF) -A/oc/F polystyrene or poly(THF)-Woc/c-polysty-rene-Wock-PMMA were synthesized via combination of living cationic and copper-catalyzed living radical polymerizations.381,388 Anionically synthesized star polymers of e-caprolactone and ethylene oxide have... 

The first two steps in the synthesis of melanin are catalyzed by tyrosinase, a copper-containing oxidase, which converts tyrosine to dopaquinone. All subsequent reactions presumably occur through nonenzymatic auto-oxidation, in the presence of zinc, with formation of the black to brown pigment eumelanin. The yellow to reddish brown, high-molecular-weight polymer known as pheomelanin and the low-molecular-weight trichromes result from addition of cysteine to dopaquinone and further modification of the products. Pheome-lanins and trichromes are primarily present in hair and feathers. 

Copper or iron phthalocyanines encapsulated inX or Y zeolites [25g], which catalyze the oxidation of cyclohexane to Ol/One and to AA with oxygen (in the presence of small amounts of t-BuOOH) at near-ambient conditions. The catalyst remains in the solid phase throughout the reaction, and can be easily filtered off. Moreover, the solvent type affects performance best selectivity to AA (41%) is achieved with methanol [25g], at 12.7% cyclohexane conversion, with a halogen-substituted phthalocyanine of Fe encapsulated in an X zeolite. Cyclohexanone and cyclohex-andione are hypothesized to be the intermediate compounds of the reaction. Incorporation of the zeolite-encapsulated Fe phthalocyanine inside a polymer matrix can serve to enhance catalyst stability and limit leaching phenomena [25h[. 

CHLORCYAN (506-77-4) Violent polymerization can be caused by chlorine or moisture. Violent reaction with alcohols, acids, acid salts, amines, strong alkalis, olefins, strong oxidizers. In crude form, this chemical trimerizes violently if catalyzed by traces of hydrogen chloride or ammonium chloride. Prolonged storage may cause the formation of polymers. Alkaline conditions will convert this chemical to cyanide. Corrodes brass, copper, bronze. 

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