Crystalline Monomer

The ratio of reactants had to be controlled very closely to suppress these impurities. Recovery of the acrylamide product from the acid process was the most expensive and difficult part of the process. Large scale production depended on two different methods. If soHd crystalline monomer was desired, the acrylamide sulfate was neutralized with ammonia to yield ammonium sulfate. The acrylamide crystallized on cooling, leaving ammonium sulfate, which had to be disposed of in some way. The second method of purification involved ion exclusion (68), which utilized a sulfonic acid ion-exchange resin and produced a dilute solution of acrylamide in water. A dilute sulfuric acid waste stream was again produced, and, in either case, the waste stream represented a... 

The largest production of acrylamide is in Japan the United States and Europe also have large production faciUties. Some production is carried out in the Eastern Bloc countries, but details concerning quantities or processes are difficult to obtain. The principal producers in North America are The Dow Chemical Company, American Cyanamid Company, and Nalco Chemical Company (internal use) Dow sells only aqueous product and American Cyanamid sells both Hquid and sohd monomer. In Europe, Chemische Eabrik Stockhausen Cie, Ahied CoUoids, The Dow Chemical Company, and Cyanamid BV are producers Dow and American Cyanamid are the only suppHers to the merchant market, and crystalline monomer is available from American Cyanamid. Eor Japan, producers are Mitsubishi Chemical Industries, Mitsui Toatsu, and Nitto Chemical Industries Company (captive market). Crystals and solutions are available from Mitsui Toatsu and Mitsubishi, whereas only solution monomer is available from Nitto. 

Estimated production capacity for the Japanese producers is 77,000 t/yr for the American producers, about 70,000 t/yr and for the European producers about 50,000 t/yr (104). The Hst prices for the monomer have increased dramatically over the past 15 years, according to the ChemicalM.arketing Reporter (105). In 1975 the price for 50% solution was 0.903/kg, compared to 1.68/kg in December 1990 (100% basis, FOB plant). The sohd crystalline monomer always demands a premium price because of the added cost of production, and sold in December 1990 for 2.27/kg compared to 1.09/kg in 1975. There are at least 35 supphers of acrylamide monomer most of them obviously are repackagers. 

Although most of the macrocycles that contain phosphorus or arsenic which have thus far been prepared, are primarily transition metals binders, two compounds have been prepared which are essentially crown ethers containing phosphorus. Kudrya, Shtepanek and Kirsanovhave prepared two compounds which are essentially polyoxygen macrocycles but which contain one or two methylphosphonic acid esters as part of the ring. These two macrocycles are shown below as 7d and 17 and are both prepared by the reaction of 2,2 [oxybis(ethyleneoxy)] bisphenolate with methylphosphonic dichloride in a mixture of acetonitrile and benzene. The crystalline monomer 16) and dimer 17) were isolated in 17% and 11% yields respectively as indicated in Eq. (6.13). 

Figure 10. Polymerization of acrylonitrile at 20°C in an intimate mixture with a highly divided polyacrylonitrile obtained by pre-irradiation of the crystalline monomer at 95°C (20). Doses of pre-irradiation of 0.11 Mrad (curve 2) to 3.14 Mrad (curve 12). The broken curve 1 pertains to the polymerization of pure acrylonitrile curve 13 is obtained in the presence of polyacrylonitrile pre-poly-...

Polymerization is usually carried out by heating in an open aluminum mold in an air-circulating oven. The crystalline monomer melts and, over a period of days, forms a dark green "B-staged" resin, which eventually solidifies into a rubber and finally a glass. 

There are numerous examples of solid state polymerizations. Here we will briefly describe examples based on addition polymers. Generally, the crystalline monomer is irradiated with electrons or some form of high-energy radiation, such as gamma or x-rays. Since many monomers are solids only below room temperature, it is customary to begin irradiation at lower temperatures with the temperature raised only after initial polymerization occurs. (Some reactions are carried to completion at the lower temperature.) After polymerization, the monomer is removed. Table 6.10 contains a list of some of the common monomers that undergo solid-state irradiation polymerization. 

Eq. 2-248) [Braun and Wegner, 1983 Hasegawa et al., 1988, 1998]. This polymerization is a solid-state reaction involving irradiation of crystalline monomer with ultraviolet or ionizing radiation. The reaction is a topochemical or lattice-controlled polymerization in which reaction proceeds either inside the monomer crystal or at defect sites where the product structure and symmetry are controlled by the packing of monomer in the lattice or at defect sites, respectively. 

The ampoule A was charged with the crystalline monomer, a phial P of initiator (e g. PFj solution), and a magnetic breaker M and then sealed at B to the rest of the rig which was then evacuated. Methylene chloride was distilled in from a reservoir on the vacuum line to dissolve the monomer and was then pumped off slowly, and evacuation was continued for 8 h, which process produced an efficient final drying. The purpose of the two pumping ducts C and D is to circumvent the evacuation obstacle presented by the sintered filter S. The required volume of solvent was then distilled into A, the rig sealed off from the line at E, and the ampoule A brought to the right... 

Work along these lines could give a better understanding of the role played by ions in the radiation chemistry of polymers. The fact that ions can induce chemical reactions in irradiated organic solids is clearly demonstrated by the polymerization of certain crystalline monomers which are known to polymerize only when treated with ionic catalysts (3). 

Polycyanurates and polyimides can be classified as thermally stable polymers. Other groups that react at high temperatures (higher than the melting temperature for crystalline monomers) can be used (Table 2.14). The reaction may be classified as an addition polymerization, but the mechanisms are very complex and not always well known. 

For the synthesis of acrylamide in a miniemulsion polymerization process, the solid crystalline monomer has to be dissolved in water, and therefore a higher amount of water was applied for the synthesis. As the continuous phase, cyclohexane or IsoparM were chosen. The miniemulsions after sonication show only a low stability (less than 1 h) without the addition of a strong lipophobe (1 mol/1 NaCl) its presence increases the stability of the miniemulsions to the timescale of several days. A polymerization started with AIBN from the continuous phase resulted in stable polymer dispersions, as shown in Fig. 11. 

An additional advantage of the use of reactive, photopolymerisable liquid crystalline monomers with charge transfer or electroluminescent properties is the ability to generate circularly and linearly polarised light. This possibility... 

The order must then be frozen in before crystallisation occurs, since this would result in the formation of grain boundaries and a reduction in transport or emission efficiency. Device breakdown is also a possibility. The most efficient way to fix the liquid crystalline order is the formation of anisotropic networks by the polymerisation of reactive mesogens in the liquid crystalline state.Anisotropic polymer networks formed from the thermal or photoinitiated polymerisation of polymerisable, so-called photoreactive, liquid crystalline monomers have been used in a wide variety of electrooptic applications, see Chapter This is a more attractive approach than cross-linking... 

Synonyms and trade names propenamide, acrylic amide, acrylagel thylene-carboxamide, amresco acryl-40, optimum Use and exposure Acrylamide is an organic solid of white, odorless, flakelike crystals. The crystalline monomer is a colorless-to-white, free-flowing crystal that is very soluble in water, alcohol, and ether and insoluble in... 

Self-standing nanostructured two-dimensional polymer films were prepared by in situ photopolymerization of ionic liquid crystalline monomer 11 that forms homeotropic monodomains of the smectic A phase on a glass plate (Figure 25.4). The film of 12 has a macroscopically oriented layered nanostructure as presented in Figure 25.5. 

Figure 25.4 Molecular structures of ionic liquid crystalline monomer 11 and polymer 12.

Gangadhara et al. have linked the cyanobiphenyl mesogen via a dicarbox-imide-group to an oxanorbornene ring system Vl-n, n=2-8 (see Fig. 4). Polymerization was carried out with Schrock type initiator 4. The dicarboximide linkage probably hindered the formation of LC phases even the introduction of relatively long spacers between the polymer backbone and the mesogen did not lead to liquid crystalline monomers or polymers [41]. 

Statistical copolymerization of SCLC-monomers with non-liquid crystalline monomers leads to dilution of the mesogenic units in the polymer, and (below a critical value) to the loss of the LC behavior of the polymer [47]. 

The introduction of perfluorinated groups generally favors microphase separation due to the immiscibility of fluorocarbons with hydrocarbons [66]. Norbornene derivatives with perfluorinated endgroups in the side chain were prepared by Wewerka et al. [67]. Monomer XII contained a relatively long (CF2)8-chain, separated via a long spacer (11 methylene-groups) from the norbornene, whereas monomer XIII has two relatively short (CH2)2(CF2)4-side chains (Fig. 11). Homopolymers and block copolymers were synthesized with one fluorinated monomer (XII or XIII) and one non-fluorinated non-liquid crystalline monomer (NBDE or COEN) with the Schrock-type initiators 4 and 5, respectively, leading to microphase-separated block copolymers. Table 9 and Table 10 summarize the physico-chemical properties of the homopolymers and block copolymers. 

Ferroelectric liquid crystalline monomers (Fig. 21, XXXVII) bearing two terminal vinyl groups were polymerized directly from their smectic A" liquid crystal phase using a Grubbs-type initiator. 

The investigation on oriented polymeric networks obtained by the photopolymerization of oriented low molecular weight species, as presented in this paper, has been carried out with a more or less conventional acrylate monomer. Already with this material an anisotropy in properties could be demonstrated. It is to be expected that even more pronounced effects can be obtained with monomers which have a strong tendency to alignment. Based on this idea we are now investigating liquid crystalline monomers in our laboratory. 

IR and NMR spectroscopy revealed that most of these compounds possess a trans-,trans-conformation and this was confirmed also for several photopolymerizable crystalline monomers by X-ray crystallographic analysis (see Sect. IV. a). 

The polymerization of N-carboxy-a-amino acid anhydrides (Leuchs anhydrides) has also been achieved by water and by a variety of bases like amines, alkali metal hydroxides, alkali metal oxides, and organo-metallic compounds in bulk, inert solvents, or starting with the solid monomer (705). Despite a great interest in the polypeptides produced in these reactions, little attention has been paid to conditions which yield solid polymer. In case the solid was produced, no physical chemical analysis of the polymer was carried out. Pol5mierization of the crystalline monomer was already observed in 1940 705). 

The polymerization of crystalline monomers needs a special mention because a larger effort has been expended in this field (75—75). The survey of the studied reactions has produced three major cat ories polycondensations, free radiacal pol5nnerizations, and ring opening polymerizations. 

Polycondensations of aminoacids and oligoamids have led only to successive pol5mierization and crystallization with a loss of the initial orientation. A seeming exception, the poljonerization of e-aminocaproic acid from the solid state which produced oriented pol5mier crystals was shown to be an epitactic pol5nnerization and crystallization (75). Some of the reactions were topochemical since they followed a reaction path only possible from the crystalline monomer, but none of the investigated cases demonstrated a solid state path from the monomer to the polymer crystal. 

Free radical polymerization from crystalline monomers is even more difficult. Besides the general conditions for a topotactic polymerization to provide the proper geometry for monomer approach for reaction and... 

Oligofluorenes studies have been performed by Wegner and coworkers [18,57,86,87] and others [88,89]. The packing frustration evident in the PF2/6 polymer is already present in the chains as short as a trimer [89]. Even at this short length thin films exhibit mesotropic-type phases [89] as opposed to the crystalline monomer samples. 

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