Peroxide-catalyzed polymerization

WeVe seen only a few examples of radical reactions because they re 1< common than polar reactions. Those we have studied can be dassified as eith radical addition reactions or radical substitution reactions. Radical additio-such as the benzoyl peroxide-catalyzed polymerization of alkene monome (Review Table 1, reaction Ij), involve the addition of a radical to an unsaturated substrate. The reaction occurs through three kinds of steps, all of whicli involve odd-electron species (1) initiation, (2) propagation, and (3) termination. 

Figure 1. NMR spectra of homopolymer from peroxide catalyzed polymerization of the exo adduct at 155°C (a), and the endo adduct at 120°C (b).

A kinetic study on a hydrogen peroxide catalyzed polymerization of butadiene at an air/water interface was also reported, although the formation of a 2-D network was not discussed Gee, G. and Davies, C.B. (1939) Trans. Faraday Soc., 35, 1298. 

Polymerization of olefins such as styrene is promoted by acid or base or sodium catalysts, and polyethylene is made with homogeneous peroxides. Condensation polymerization is catalyzed by acid-type catalysts such as metal oxides and sulfonic acids. Addition polymerization is used mainly for olefins, diolefins, and some carbonyl compounds. For these processes, initiators are coordination compounds such as Ziegler-type catalysts, of which halides of transition metals Ti, V, Mo, and W are important examples. 

Methyl ethyl ketone may also he produced hy the catalyzed dehydrogenation of sec-hutanol over zinc oxide or brass at about 500°C. The yield from this process is approximately 95%. MEK is used mainly as a solvent in vinyl and acrylic coatings, in nitrocellulose lacquers, and in adhesives. It is a selective solvent in dewaxing lubricating oils where it dissolves the oil and leaves out the wax. MEK is also used to synthesize various compounds such as methyl ethyl ketone peroxide, a polymerization catalyst used to form acrylic and polyester polymers and methyl pentynol by reacting with acetylene ... 

The polymeric pyrrolic autoxidation products probably result from the oxidized monomeric systems, which are analogous in structure to those isolated from photooxidation and peroxide oxidation reactions. Thus, for example, analysis of the products of the autoxidation of 1-methylpyrrole (Scheme 47) would suggest that 1 -methyl-A3-pyrrolin-2-one (153) is initially formed from a radical reaction of the pyrrole with triplet oxygen. This reaction sequence should be compared with that proposed for the oxidation of pyrroles with hydrogen peroxide (Scheme 50), which yields (181), (182) and (183) as the major isolable products. The acid-catalyzed reaction of a pyrrole with its oxidation product e.g. 153) also results in the formation of polymeric material and the formation of pyrrole black is probably a combination of oxidation and acid-catalyzed polymerization processes. 

Gindin, Abkin, and Medvedev (21) observed several of the characteristics of copolymerizations involving charge transfer intermediates in the benzoyl peroxide-catalyzed copolymerization of butadiene with acrylonitrile and methacrylonitrile. Irrespective of the initial concentrations, polymerization ceased when one of the components was consumed. The butadiene-acrylonitrile copolymer had a 67% alternating structure, while the butadiene-methacrylonitrile copolymer had an 80% alternating structure. 

Polymerization of Styrene Solutions of Volatile Hydrocarbons. Addition of Hydrocarbon before Polymerization. Bulk Polymerization. Expandable polystyrene was prepared inadvertently in 1945 in an attempt to bulk copolymerize 10% isobutylene with styrene. The product formed a low density foam when heated (96). An early method (1950) for rendering polystyrene expandable by petroleum ether was to dissolve 6 parts of petroleum ether in a 40% solution of polystyrene in benzoyl peroxide-catalyzed styrene and to hold the mass for 28 days at 32 °C. (124). In a recent version of this process, the monomer (chlorostyrene) and blowing agent (trichlorofluoromethane) in a poly (vinyl fluoride) bag were irradiated with y-rays (105). 

Possible causes of radical formation in the polymer chain are residues of transition metals and peroxides used to catalyze polymerization and thermo-oxidative processes. Whatever causes homolytic bond scission to produce free radicals (eq 8.1 and 8.2), oxygen reacts with the resultant radical to generate hydroperoxide moieties. Key reactions involved in the initiation and propagation of radicals are illustrated in eq 8.1-8.4, where is a polymeric fragment ... 

A bienzymatic system was developed as catalyst for the oxidative polymerization of phenols.18 The HRP-catalyzed polymerization of phenol in the presence of glucose oxidase and glucose gave the polymer in a moderate yield, in which hydrogen peroxide was formed in situ by the oxidative reaction of glucose catalyzed by glucose oxidase. 

Redox catalyzed polymerizations using ferrous ion and peroxidative compound have been reported to be usefiil for grafting reaction of natural fiber such as chitosan (79). Ascorbic acid is also used instead of the ferrous ion 80). Ascorbic acid is reported to produce activated oxygen under mild condition, and recently it is used for linear polymer synthesis of sugar alcohol derivatives containing vinyl group 81). These catalysts, which promote the reaction under... 

Polystyrene Polyisoprene (cis) Polyisobutylene CH2=CHPh CH, CH2=CH-C=CH2 CHj / CH2=C CHa peroxide-catalyzed radical-chain polymerization coordination or butyllithium-catalyzed anionic polymerization low-temperature cationic polymerization, BF3 and AIQ3 catalysis... 

Uses Reducing agent in redox-catalyzed polymerization color stabilizer, modifier, catalyst for polyamides antioxidant intermediate for forming metallic salts used as stabilizers accelerator for org. peroxide catalysts improver of polysiloxane resins free radical promoter in emulsion polymerization promoter in polyester resin curing mfg. of self-extinguishing fibers (reacts with polyester resin and polyolefin) color/odor inhibitor, catalyst for some thermoplastics discoloration inhibitor in PE corrosion inhibitor on thin aluminum surfs. lubricity improver in polyphenyl thioether-based lubricants Manuf./Distrib. Akzo Nobel http //www.akzonobel.com, Ferro http //WWW. ferro. com... 

Uses Initiator for radical catalyzed polymerization of vinyl monomers Manuf/Distrib. Akzo Nobel http //www.akzonobel.com-, Aztec Peroxides Trade Name Synonyms Aztec TBPND t[Aztec Peroxides] Aztec TBPND-40-EAQ f[Aztec Peroxides] Aztec TBPND-75-OMS flAztec Peroxides] Luperox 10 [Atofina SA http //www.atofina.com-, Atofina http //www.atofinachemicals.com]-, Lupersol 10 t[Atofina N. Am./Org. Peroxides Atofina SA http //WWW. atofina. com]... 

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