Monomeric acrylonitrile

Ability to analyze unreacted monomers was dependent on detector selectivity. The UV detector was operated at 254 nm for analysis of AN/S latex solutions. Styrene is a strong UV abosrber at this wavelength while acrylonitrile has no measurable absorbance at 254 nm. Thus, the UV detector was entirely selective to monomeric styrene. The refractometer detector was sensitive to both acrylonitrile and styrene when each was present in the desired copolymer proportions (70/30). However,... 

Butadiene and isoprene have two double bonds, and they polymerize to polymers with one double bond per monomeric unit. Hence, these polymers have a high degree of unsaturation. Natural rubber is a linear cis-polyisoprene from 1,4-addition. The corresponding trans structure is that of gutta-percha. Synthetic polybutadienes and polyisoprenes and their copolymers usually contain numerous short-chain side branches, resulting from 1,2-additions during the polymerization. Polymers and copolymers of butadiene and isoprene as well as copolymers of butadiene with styrene (GR-S or Buna-S) and copolymers of butadiene with acrylonitrile (GR-N, Buna-N or Perbunan) have been found to cross-link under irradiation. 

Copolymerisation is a process in which a mixture of more than one monomeric species is allowed to polymerise. The copolymer contains multiple units of each monomer in the chain. The examples are copolymers of 1,3-butadiene and st3rrene and 1, 3-butadiene and acrylonitrile. 

Similarly to homopolymers, source-based nomenclature has been applied to copolymers [4]. The principal problem is to define the kind of arrangement in which various types of monomeric units are related to each other. Seven types of separate arrangements have been defined, which are shown in Table 1, where A, B and C represent the names of monomers. The monomer names are linked either through an italicized qualifier or connective (infix), such as -CO- , to form the name of the copolymer, as in poly(styrene-co-acrylonitrile). The order of citation of the monomers is arbitrary. 

Monomeric acrylonitrile is distilled under nitrogen into a suitable receiver (see Sect. 2.2.S.3). Butadiene from a cylinder is condensed under nitrogen atmosphere into a trap cooled in a methanol/dry ice bath. 

Acrylonitrile. Another monomeric raw material that is produced from ethylene is acrylonitrile. The present commercial process involves the oxidation of ethylene to ethylene oxide which reacts with hydrogen cyanide and dehydrates to acrylonitrile. 

Butadiene is used primarily in the production of synthetic rubbers, including styrene-butadiene rubber (SBR), polybutadiene nibber (BR), styrene-butadiene latex (SBL), chloroprene rubber (CR) and nitrile rubber (NR). Important plastics containing butadiene as a monomeric component are shock-resistant polystyrene, a two-phase system consisting of polystyrene and polybutadiene ABS polymers consisting of acrylonitrile, butadiene and styrene and a copolymer of methyl methacrylate, butadiene and styrene (MBS), which is used as a modifier for poly(vinyl chloride). It is also used as an intermediate in the production of chloroprene, adiponitrile and other basic petrochemicals. The worldwide use pattern for butadiene in 1981 was as follows (%) SBR + SBL, 56 BR, 22 CR, 6 NR, 4 ABS, 4 hexamethylenediamine, 4 other, 4. The use pattern for butadiene in the United States in 1995 was (%) SBR, 31 BR, 24 SBL, 13 CR, 4 ABS, 5 NR, 2 adiponitrile, 12 and other, 9 (Anon., 1996b). 

Inspection of Table 8.14 reveals that a lot of nitrogen containing products are among the products of pyrolysis. Styrene is the most significant product or thermal decomposition. Also dimers and trimers from styrene and monomeric acrylonitrile are main products in the pyrolysis oil. 

In a conventional emulsion process, the conversion of the monomers to the copolymers reaches 97%. Unreacted monomers in general are problematic with respect to pollution. In particular, unreacted monomeric acrylonitrile (AN) is known to be highly toxic. It has been shown that the conversion can be increased by the addition of certain antioxidants (3). 

A constant fraction of the monomer is converted to graft copolymer for the reactions of methyl methacrylate and methyl acrylate with SBS this is independent of the amount of monomer and the amount of initiator. Both homopolymer and graft copolymer are formed and 25 - 30% of the monomeric methyl methacrylate reacts to form the graft copolymer while the remainder forms homopolymer the fraction of graft copolymer is close to 40% for methyl acrylate. This is also true for the reaction of acrylonitrile with polystyryllithium, here the amount of graft copolymer is a little lower, in the range of 15 - 20%. ... 

Acrylics. Acrylics are produced by the polymerization of acrylonitrile. They have a chemical structure essentially comprising the repeating unit, [ —CH2—CH(CN)—]n, with up to 15 percent of the polymer comprising one or two other monomeric units. As comonomers, vinyl acetate and an acrylate or methacrylate ester is used to vary the properties of the polymer for both ease of processing into a fiber and for improved fiber properties [8]. 

If the excited ethylene dimer exists as an ion radical pair, propagation may incorporate both monomeric units of the dimer, analogous to the behavior of comonomer charge transfer complexes such as butadiene-maleic anhydride, or only one unit, as noted in the homopolymerization of N-vinylcarbazole in the presence of electron accepting monomers such as acrylonitrile and maleic anhydride. 

Use Reactive monomer that may be copolymerized with a variety of unsaturated monomeric materials, including acrylonitrile, vinyl chloride, vinylidene chloride, and vinyl acetate to yield internally plasticized resins. 

Tirrell and co-workers studied copolymerization of styrene (S) and acrylonitrile (A) using l,l -azobis(l-phenylethane)-a,q/-13C, which generates a monomeric styrene radical, 1-phenylethyl radical 87... 

The above examples show the complexity of the systems involving radical-anions derived from compounds of higher electron-affinity. It is not surprising, therefore, that benzophenone ketyl and other similar compounds do not initiate styrene polymerization, although they initiate polymerization of acrylonitrile or methyl-methacrylate. On the other hand, the monomeric dianions of benzophenone initiate polymerization of styrene as well as of other monomers, but not of vinyl chloride or acetate. Mechanisms of these initations were not investigated and presumably are complex. 

Statistical copolymers are those in which the monomer sequence follows a specific statistical law (e.g., Markovian statistics of order zero, one, two). Random copolymers are a special case of statistical copolymers in which the nature of a monomeric unit is independent of the nature of the adjacent unit (Bernoullian or zero-order Markovian statistics). They exhibit the structure shown in Figure 6.1. If A and B are the two monomers forming the copolymer, the nomenclature is poly (A-stat-B) for statistical copolymers and poly (A-ran-B) for the random case. It should be noted that sometimes the terms random and statistical are used indistinctly. The commercial examples of these copolymers include SAN poly (styrene-ran-acrylonitrile) [4] and poly (styrene-ran-methyl methacrylate) (MMA) [5]. 

Copolymerization of 18 with styrene and acrylonitrile In the range of 40 to 60 mol % of the metallomonomer the copolymer composition does not depend on the monomeric mixture. The copolymers are soluble in benzene the molecular weights are about 10 Da. Under copolymerization conditions (75 °C, benzene, 1% of the initiator) of 18 with acrylonitrile (25 mol %) a light-yellow product containing -12% vanadium was obtained. The yield was 15%, the product is soluble in DMFA and DMSO, and its intrinsic viscosity was 0.11 (DMSO, 30 °C). IR 1720 (vc=o), 2245 cm (vc n) the ratio of the intensities of the absorptions /(C=0)//(C=N) = 13 1. This method can also be used for the synthesis and polymerization of optically active metallomonomers. 

Some oriented polymers only exhibit sharp X-ray diffractions at the equator. In such cases, the macromolecules must be packed in two-dimensional lateral order. However, the monomeric units in each polymer chain are randomly arranged, because of either a random displacement of polymer chains with respect to their neighbors, or a random distribution of monomeric units within each chain or because of irregular chain structure with respect to tacticity. Poly(acrylonitrile) is an example of the last case, and poly(ethylene-/7-carboxyphenoxyundecanoate) is an example of the first case. 

Figure 9-31. Relationship between the constant Ke of the molar mass relationship [rj] = Ke and the formula molar mass Mu of the monomeric units in polymers of the type (—CH2—CHR—) (O) or (—CH2-CRR —) ( ), PE, poly(ethylene) PVAl, poly(vinyl alcohol) PAN, poly(acrylonitrile) PVC, poly(vinyl chloride) PVPy, poly(2-vinyl pyridine), PVCz, poly(A -vinyl carbazole). The figures give the slope.

The polyacrylates were synthesized with deuterium labels on the methine position on the backbone. The monomeric acrylates were made by the exchange of the methine proton on acrylonitrile with D2O, hydroquinone and CaO, as previously reported for iso-propyl acrylate.(i) The nitrile group was converted to the appropriate ester with the appropriate alcohol and sulfuric acid. Since our first report, a more facile synthesis of these monomers has been reported.(T) The polymerizations were carried out in toluene using azobis-/so-butyronitrile (AIBN) as an initiator. The reaction scheme is given below. 

Metal ketyls form in reactions of alkali metals with aromatic ketones in some polar solvents, like dioxane or tetrahydrofuran. These ketyls exist in equilibrium mixtures of monomeric anion radicals and dimeric dianions.Originally, there was some controversy about the mechanism of initiation of monomers like acrylonitrile or methyl methacrylate by sodium benzophenone. The following mechanism was derived from spectral evidence. The initiation is by transfer of the electron and the ion charge " ... 

Figure 22-7. Change in mole fraction of monomeric unit, of the reversibly polymerizing a-methyl styrene in the free radical copolymerization with methyl methacrylate at 60 C (above) or with acrylonitrile at 80 C (below) as a function of the overall monomer concentration. In the former case, reversibly depolymerizing disequences (—), and in the latter case, nondepolymerizing disequences (—), were found. (After data from P. Wittmer.)...

The commercial names of polymers do not always fulfill what they promise. Not only more or less branched homopolymers of various molar masses are encountered under the name, poly(ethylene), but also copolymers of ethylene with propylene, butene-1, etc. Commercially, not only the homopolymers of styrene are included under the poly(styrene) designation, but also copolymers with acrylonitrile (SAN), blends of poly(styrene) with various elastomers (HIPS = high impact poly(styrene)) and graft copoly-mers-blends of acrylonitrile, butadiene, and sytrene. The styrene monomeric unit is the main component in all of these polymers thus, these polymers are all included in the poly(styrene) family, although their properties can differ from each other (Table 36-4). 

All diene rubbers discussed so far, natural rubber, styrene-butadiene rubbers, poly-butadienes), butyl rubbers, and ethylene-propylene rubbers, consist of aliphatic or aromatic monomeric units. They swell readily in aliphatics they have poor oil resistance. But the free radical copolymerization of acrylonitrile with butadiene leads to what is known as nitrile rubber, which has good oil resistance because of the many polar nitrile groups. However, the rebound elasticity and the low-temperature flexibility decrease with increasing nitrile fraction. Consequently, NBR is mainly used for fuel hoses, motor gaskets, transport belts, etc. 

On the other hand, small amounts of flame-retardant monomeric units are polymerized directly into the chain molecule of synthetic fibers such as poly(acrylonitrile) and poly(ethylene terephthalate). The flame retardants are bound so strongly into the chain that, in contrast to low-molar-mass substances, they cannot be removed by repeated washing of the textiles. To a limited extent, however, PAN, PET, and PP are also made fire resistant by addition of additives previous to or at the spinning stage. 

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