Polymerization Low temperature

CH2=CHC = CCH = CH2. a colourless liquid which turns yellow on exposure to the air it has a distinct garlic-like odour b.p. 83-5°C. Manufactured by the controlled, low-temperature polymerization of acetylene in the presence of an aqueous solution of copper(I) and ammonium chlorides. It is very dangerous to handle, as it absorbs oxygen from the air to give an explosive peroxide. When heated in an inert atmosphere, it polymerizes to form first a drying oil and finally a hard, brittle insoluble resin. Reacts with chlorine to give a mixture of chlorinated products used as drying oils and plastics. 

Technora. In 1985, Teijin Ltd. introduced Technora fiber, previously known as HM-50, into the high performance fiber market. Technora is based on the 1 1 copolyterephthalamide of 3,4 -diaminodiphenyl ether and/ -phenylenediamine (8). Technora is a whoUy aromatic copolyamide of PPT, modified with a crankshaft-shaped comonomer, which results in the formation of isotropic solutions that then become anisotropic during the shear alignment during spinning. The polymer is synthesized by the low temperature polymerization of/ -phenylenediamine, 3,4 -diaminophenyl ether, and terephthaloyl chloride in an amide solvent containing a small amount of an alkaU salt. Calcium chloride or lithium chloride is used as the alkaU salt. The solvents used are hexamethylphosphoramide (HMPA), A/-methyl-2-pyrrohdinone (NMP), and dimethyl acetamide (DMAc). The stmcture of Technora is as follows ... 

Linear polyethyleneimine results only in low yields from low temperature polymerization of ethyleneimine for very long reaction times. It can, however, be synthesized in a targeted manner by polymerization of 2-oxazolines with subsequent hydrolytic cleavage of the resulting polyamides (355,358). 

Water. Latices should be made with deionized water or condensate water. The resistivity of the water should be at least lO Q. Long-term storage of water should be avoided to prevent bacteria growth. If the ionic nature of the water is poor, problems of poor latex stabiUty and failed redox systems can occur. Antifreeze additives are added to the water when polymerization below 0°C is required (37). Low temperature polymerization is used to limit polymer branching, thereby increasing crystallinity. 

The mechanism of ion polymerization in formaldehyde crystals proposed by Basilevskii et al. [1982] rests on Semenov s [1960] assumption that solid-phase chain reactions are possible when the arrangement of the reactants in the crystal prepares the configuration of the future chain. The monomer crystals capable of low-temperature polymerization fulfill this condition. In the initial equilibrium state the monomer molecules are located in the lattice sites and the creation of a chemical bond requires surmounting a high barrier. However, upon creation of the primary dimer cation, the active center shifts to the intersite, and the barrier for the addition of the next link... 

Polymers containing oxalic acid can be prepared from their esters.57 With the reactive esters the prepolymers can be synthesized at low temperatures. Polymerization of these prepolymers is possible at 270°C. 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

Although the low temperature polymerization of methyl methacrylate in polar solvents such as THF was believed to proceed without termination, a more exhaustive investigation55) revealed some slow termination processes resulting from the formation of a, not yet specified agent, supposedly produced in the initiation step. Since the nature of the terminating agent is still unknown it is premature to discuss here the proposed schemes of this termination process. 

Low temperature polymerization, 79 719 Low temperature properties, of ethylene-acrylic elastomers, 70 699-700... 

Monomer conversion efficiencies for latex production range from 60% for low-temperature polymerization to 98% for high-temperature conversion. 

The low temperature polymerization of isobutylene (that is, polymerization at temperatures below about —70°) in the presence of Friedel-Crafts catalysts (particularly boron fluoride, aluminum chloride, and titanium tetrachloride, has been studied quite intensely. The reaction is commercially important because it yields a high molecular weight... 

A more complete and detailed discussion of the low temperature polymerization of isobutylene cannot be given here. The interesting comments on the work of Evans, Polanyi, and co-workers (83 and 84) which have been published with the papers are well worth studying. 

Evidence in support of a carbonium ion type of mechanism for low temperature polymerization was also obtained in an investigation of the kinetics of the homogeneous liquid phase polymerization of propene in the presence of aluminum bromide and hydrogen bromide at about —78° (Fontana and Kidder, 89). The rate of reaction is approximately proportional to the concentration of the promoter, no polymerization occurring in its absence. During the main portion of the reaction, the rate is independent of the monomer concentration toward the end, it decreases, due apparently to the low-concentration of the monomer, addition of more olefin resulting in an increase in the rate. It was concluded that the reaction involves an active complex, which may be regarded as a carbonium ion coupled with an anion ... 

Both Ni and Pd initiators polymerize propene to give a combination of different microstructures, including 1,2- and 3,1-placements as well as methyl branches (via 2,3-placement) and long-chain branching. Room-temperature polymerizations with both Ni and Pd initiators yield atactic polypropene. Low temperature polymerizations proceed by chain end control to yield moderate syndioselectivity, (rr) as high as 0.8, but usually less [Busico and Cipullo, 2001 McCord et al, 2001 Pappalardo et al., 2000 Zambelli et al., 2001]. 

The temperature dependency of 1,2 content shown in Table II is also consistent with complex formation between polybutadienyl-lithium and the oxygen atom in the lithium morpholinide moleculre. One can visualize an equilibrium between noncom-plexed and complexed molecules which would be influenced by temperature. Higher temperatures would favor dissociation of the complex and, therefore, the 1,2 content of the polymer would be lower than that from the low temperature polymerization. This explanation is supported by the polymerization of butadiene with lithium diethylamide, in which the microstructure of the polybutadiene remains constant regardless of the polymerization temperature (Table IV). This is presumably due to the fact that trialkylamines are known to be poor... 

Methyl chloride is used in the production of tetramethyllead antiknock compounds for gasoline and methyl silicone resins and polymers, and as a catalyst carrier in low-temperature polymerization (e g., butyl rubber), a refrigerant, a fluid for thermometric and thermostatic equipment, a methylating agent in organic synthesis, an extractant and low-temperature solvent, a herbicide, a topical antiseptic, and a slowing agent (lARC, 1986 Lewis, 1993). 

Later, Ewen reported low-temperature polymerization of propylene with a Cp2Ti(C6H5)2-MAO system leading to an isotactic polymer (139, 140). With ethylene-bridged bisindenyls as ligands of Ti (141), two diastereomers are possible (Scheme 64). The chiral Ti complex (ra-... 

Vinyl-type addition polymerization can also be carried out with acidic catalysis such as boron tnfluoride or tin tetrachloride and with basic catalysis such as alkali melals or alkali alkyls. An example of the first ease is the low-temperature polymerization of isobutene, which gives Vistanex" and butyl rubber an example of the second type is the polymerization of butadiene with sodium, which leads to buna rubber. 

In the low temperature polymerization of these esters by the action of hydrogen atoms at room temperature cyclization is, on the contrary, of little importance66. Thus... 

The first example of Iiving polyolefin with a uniform chain length was found in the low-temperature polymerization of propylene with the soluble catalyst composed of V(acac)3 and Al(C1Hi)2Cl. The mechanism of the living coordination polymerization is discussed on the basis of the kinetic and stereochemical data. Subsequently, some applications of living polypropylene are introduced to prepare tailor-made polymers such as terminally functionalized polymers and block copolymers which exhibit new characteristic properties. Finally, new types of soluble Ziegler-Natta catalysts are briefly surveyed in connection with the synthesis of living polyolefins. 

Doi, Ueki and Keii47,48) have found that the soluble catalyst composed of V(acac)3 (acac = acetylacetonate anion) and A1(C2H5)2C1 polymerizes propylene in toluene at —78 °C to give a syndiotactic living polypropylene having a narrow molecular weight distribution (Mw/Mn = 1.05-1.20). This low-temperature polymerization of propylene was shown to satisfy all criteria for the living polymerization 47). 

The low-temperature polymerization of propylene has been performed with various types of vanadium compounds instead of V(acac)3. The results are summarized in Table 1. Vanadium compounds such as VC14, VOCl3, VO(acac)2 and VOCl2(acac) afford syndiotactic polypropylenes with rather broad MWDs, close to the most probable distribution (Mw/lVln = 2.0). At present, V(acac)3 is the sole vanadium compound being effective for the living polymerization of propylene. 

Two typical cases are illustrated in Fig. 2.24 the first scheme (Fig. 2.24 a) is related to high-temperature polymerization, in which newly formed polymer is molten and the processes of polymerization (part Ob of the full curve) and crystallization (part bK of the full curve) are separated in time. The second case (Fig. 2.24 b) illustrates low-temperature polymerization in this situation crystallization starts before the full process of polymerization is completed. This is typical superposition of two kinetic processes, and the shape of the curve in Fig. 2.24 b does not allow the separation of these processes without additional information and assumptions.The net heat effect is the same in... 

The validity of Eq. (2.55) is illustrated in Fig. 2.26, where calculated curves are compared with experimental data for two different temperature regimes of a superimposed process. It can be seen that for high-temperature polymerization, Eqs. (2.55) and (2.56) give similar results. This is to be expected, because we are dealing with time-separated processes i.e., crystallization only starts when almost all of the polymer is already present. However, for low-temperature polymerization, the situation is quite different, and the curves representing Eq. (2.55) - curve 3, and (2.56) - curve 4, do not coincide. The experimental data follow curve 3, and thus we may conclude that the model represented by Eq. (2.55) is correct because it fits the experimental data. A model for superimposed processes similar to that discussed above, was also proposed.101 In this approach, the temperature increase in a superimposed process is expressed by the following equation ... 

Bol shakov A.I., Barkalov I.M. Chain transfer effect in low-temperatures polymerizations of vinyl monomers at devitrification ethyl alcohol matrixes. Polymer Science, 23,1981, pp. 1086-1089. 

Solvent for vegetable oils, thermometers (low temperature), polymerization, paint dilutor, and used to denature alcohol. 

Polyisobutylenes. Polyisobutylenes are produced by the low temperature polymerization of high-purity isobutylene. The main com-... 

The catalyst system is prepared by mixing the two compounds in the solvent, usually at low temperatures. Polymerization occurs at specific sites on the catalyst surface. There are several proposed mechanisms for polymerization, but the important aspect of both is that the polymerization occurs in coordination... 

The complex can initiate the polymerization of acrylonitrile at room temperature1 and may also be used as a catalyst for the low-temperature polymerization of acrylonitrile. 

The most relevant early work in the context of this study is the radiation induced depolymerization of poly(phtalaldehyde) [9]. In this case, depolymerization is due to a ceiling temperature phenomenon whereby radiation induced cleavage of the polymer causes it to revert fully to monomer. Poly(phtalaldehyde) is a material with a very low ceiling temperature which is only rendered stable at room temperature through the device of capping its chain-ends after low temperature polymerization, thereby preventing its spontaneous degradation when heated. 

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