Styrene, copolymerization with butadiene

Methyl methacrylate has been copolymerized with a wide variety of other monomers, such as acrylates, acrylonitrile, styrene, and butadiene. Copolymerization with styrene gives a material with improved melt-flow characteristics. Copolymerization with either butadiene or acrylonitrile, or blending PMMA with SBR, improves impact resistance. Butadiene-methyl methacrylate copolymer has been used in paper and board finishes. 

Styrene Copolymers. Acrylonitrile, butadiene, a-methylstyrene, acryUc acid, and maleic anhydride have been copolymerized with styrene to yield commercially significant copolymers. Acrylonitrile copolymer with styrene (SAN), the largest-volume styrenic copolymer, is used in appHcations requiring increased strength and chemical resistance over PS. Most of these polymers have been prepared at the cross-over or azeotropic composition, which is ca 24 wt % acrylonitrile (see Acrylonithile polya rs Copolyp rs). 

Apart from poly(ethylene glycol), other hydroxyl-terminated polymers and low-molecular weight compounds were condensed with ACPC. An interesting example is the reaction of ACPC with preformed poly(bu-tadiene) possessing terminal OH groups [26]. The reaction was carried out in chloroform solution and (CH3CH2)3N was used as a catalyst. MAIs based on butadiene thus obtained were used for the thermally induced block copolymerization with styrene [26] and dimethyl itaconate [27]. 

Butadiene is by far the most important monomer for synthetic rubber production. It can be polymerized to polybutadiene or copolymerized with styrene to styrene-butadiene rubber (SBR). Butadiene is an important intermediate for the synthesis of many chemicals such as hexa-methylenediamine and adipic acid. Both are monomers for producing nylon. Chloroprene is another butadiene derivative for the synthesis of neoprene rubber. 

Acrylic textile fibers are primarily polymers of acrylonitrile. It is copolymerized with styrene and butadiene to make moldable plastics known as SA and ABS resins, respectively. Solutia and others electrolytically dimerize it to adiponitrile, a compound used to make a nylon intermediate. Reaction with water produces a chemical (acrylamide), which is an intermediate for the production of polyacrylamide used in water treatment and oil recovery. 

The major four-carbon feedstock molecules are 1,3-butadiene and isobutylene, both involved in the synthesis of many monomers and intermediates. Butadiene is copolymerized with styrene to form SBR and with acrylonitrile to form ABS rubbers. 

Butadiene A gaseous hydrocarbon of the diolefin series. Can be polymerized into polybutadiene or copolymerized with styrene or acrylonitrile to produce SBR and NBR, respechvely. 

Binary neodymium alk(aryl)oxide/dialkylmagnesium diene polymerization catalysts were reported by J.-F. Carpentier and coworkers [181,192], The homopolymerization of butadiene, and copolymerization with styrene and... 

Butadiene, CH2=CH-CH=CH2 (CAS No. 106-99-0 PM/Ref. No. 13630) is commonly copolymerized with styrene and acrylonitrile to make ABS or BS food contact plastics (for applications see acrylonitrile). Butadiene is a suspected carcinogen with extreme volatility (bp -4.5 °C) and low water solubility. This makes it very difficult to handle migration and calibration samples where the matrix is of highly aqueous character such as the aqueous food simulants. 

In the early 1940s, researchers at Dow produced interpolymer blends of styrene and butadiene by an emulsion process. The polymer, called Styralloy 22, was used as insulation for radar cables until it was displaced by low-density polyethylene produced by ICI. Later, Dow experimented with soluble GRS copolymerized with styrene to make high-impact polystyrene. 

Polyacrylonitrile is most often encountered as a fiber. It is also found in acrylonitrile-containing plastics copolymerized with styrene, butadiene, or methyl methacrylate. All such polymers contain nitrogen. 

The emulsion polymerization of myrcene and its copolymerization with styrene and butadiene, followed by vulcanization of the ensuing polymers to obtain synthetic rubbers was reported as early as 1948 [16] but no other such system has been mentioned in the literature since then. 

Tapered Block Copolymers. The alkyllithium-initiated copolymerizations of styrene with dienes, especially isoprene and butadiene, have been extensively investigated and illustrate the important aspects of anionic copolymerization. As shown in Table 15, monomer reactivity ratios for dienes copolymerizing with styrene in hydrocarbon solution range from approximately 8 to 17, while the corresponding monomer reactivity ratios for styrene vary from 0.04 to 0.25. Thus, butadiene and isoprene are preferentially incorporated into the copolymer initially. This type of copolymer composition is described as either a tapered block copolymer or a graded block copolymer. The monomer sequence distribution can be described by the structures below ... 

Monodispersed (polydispersity index = 1,04) polystyrene and polyisoprene with a molecular weight in the range of 2 x 10 were used as the carrier polymers by Bates and Baker [18,51]. The isoprene polymer was synthesized anionically at -78°C using toluene as the solvent. It was composed of approximately 80% cis 1,4, 15% trans-, A and 15% 3,4-disubstitutedrepeating units. A few percent (3%) of butadiene were randomly copolymerized with styrene anionically at 25°C in order to provide unsaturated moieties for the next modification step. Electrophilic sites were then introduced into the respective carrier polymers by either oxidation or epoxidation. It was expected that the sites consist mainly of aldehydes, ketones, and/or epoxides. ffj-Chloroperbenzoic acid (m-CPBA) was found to be effective in epoxidation of the unsaturated moieties in... 

Little has been published on techniques for achieving the homopolymerization of mono or disubstituted MA monomers (see Chapter 3). Thamm and Hensinger recently showed that y irradiation of dichloromaleic anhydride (DCMA) in benzene produced a polymer as the main product. The yield and molecular weight of the polymer increased with radiation dose. The polymer backbone contained chlorophenylsuccinic anhydride residues. It was shown that chlorophenylmaleic anhydride was produced during the reaction. Under the same conditions, dimethylmaleic anhydride (DMMA) failed to polymerize with free-radical, ionic, and UV initiation with sensitizers.Presumably, techniques may be found for the homopolymerization of chloro or phenyl-maleic anhydride. Chloromaleic anhydride (CMA) reacts with methyl radicals more readily than MA and much more readily than DCMA. " This, coupled with halogen activation and ring coplanarity, should allow CMA to be homopolymerized. It is known that CMA will copolymerize with styrene, methyl methacrylate, butadiene, cyanoacrylates, and other olefins. 

Styrene Copolymers, Copolymerization is another way to improve the mechanical properties and chemical resistance of polystyrene. Acrylonitrile, butadiene, alphamethylstyrene, methyl methacrylate, divinyl-benzene, maleic anhydride, and other monomers have been copolymerized with styrene to produce commercially important copolymers. Some of the most widely used of these are those prepared with acrylonitrile and butadiene. Styrene copolymerized with butadiene (SBR) is one of the more important elastomeric materials used today. (See Chapter 18.)... 

G-5—G-9 Aromatic Modified Aliphatic Petroleum Resins. Compatibihty with base polymers is an essential aspect of hydrocarbon resins in whatever appHcation they are used. As an example, piperylene—2-methyl-2-butene based resins are substantially inadequate in enhancing the tack of 1,3-butadiene—styrene based random and block copolymers in pressure sensitive adhesive appHcations. The copolymerization of a-methylstyrene with piperylenes effectively enhances the tack properties of styrene—butadiene copolymers and styrene—isoprene copolymers in adhesive appHcations (40,41). Introduction of aromaticity into hydrocarbon resins serves to increase the solubiHty parameter of resins, resulting in improved compatibiHty with base polymers. However, the nature of the aromatic monomer also serves as a handle for molecular weight and softening point control. 

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). 

A variety of trichloroethylene copolymers have been reported, none with apparent commercial significance. The alternating copolymer with vinyl acetate has been patented as an adhesive (11) and as a flame retardant (12,13). Copolymerization with 1,3-butadiene and its homologues has been reported (14—16). Other comonomers include acrylonitrile (17), isobutyl vinyl ether (18), maleic anhydride (19), and styrene (20). 

Polystyrene (PS) is the fourth big-volume thermoplastic. Styrene can be polymerized alone or copolymerized with other monomers. It can be polymerized by free radical initiators or using coordination catalysts. Recent work using group 4 metallocene combined with methylalumi-noxane produce stereoregular polymer. When homogeneous titanium catalyst is used, the polymer was predominantly syndiotactic. The heterogeneous titanium catalyst gave predominantly the isotactic. Copolymers with butadiene in a ratio of approximately 1 3 produces SBR, the most important synthetic rubber. 

The observation of Tsuji et al. 148) concerned with copolymerization of 1- or 2-phenyl butadiene with styrene or butadiene illustrates again the importance of the distinction between the classic, direct monomer addition to the carbanion, and the addition involving coordination with Li4. The living polymer of 1- or 2-phenyl butadiene initiated by sec-butyl lithium forms a block polymer on subsequent addition of styrene or butadiene provided that the reaction proceeds in toluene. However, these block polymers are not formed when the reaction takes place in THF. The relatively unreactive anions derived from phenyl butadienes do not add styrene or butadiene, while the addition eventually takes place in hydrocarbons on coordination of the monomers with Li4. The addition through the coordination route is more facile than the classic one. 

About half of the styrene produced is polymerized to polystyrene, an easily molded, low-cost thermoplastic that is somewhat brittle. Foamed polystyrene can be made by polymerizing it in the presence of low-boiling hydrocarbons, which cause bubbles of gas in the solid polymer after which it migrates out and evaporates. Modification and property enhancement of polystyrene-based plastics can be readily accomplished by copolymerization with other substituted ethylenes (vinyl monomers) for example, copolymerization with butadiene produces a widely used synthetic rubber. 

We have considerable latitude when it comes to choosing the chemical composition of rubber toughened polystyrene. Suitable unsaturated rubbers include styrene-butadiene copolymers, cis 1,4 polybutadiene, and ethylene-propylene-diene copolymers. Acrylonitrile-butadiene-styrene is a more complex type of block copolymer. It is made by swelling polybutadiene with styrene and acrylonitrile, then initiating copolymerization. This typically takes place in an emulsion polymerization process. 

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