Polymerizing solvent

The polymerization is carried out at temperatures of 0—80°C in 1—5 h at a soHds concentration of 6—12%. The polymerization is terminated by neutralizing agents such as calcium hydroxide, calcium oxide, calcium carbonate, or lithium hydroxide. Inherent viscosities of 2-4 dL/g are obtained at 3,4 -dianiinodiphenyl ether contents of 35—50 mol %. Because of the introduction of nonlinearity into the PPT chain by the inclusion of 3,4 -dianiinodiphenyl ether kinks, the copolymer shows improved tractabiUty and may be wet or dry jet-wet spun from the polymerization solvent. The fibers are best coagulated in an aqueous equiUbrium bath containing less than 50 vol % of polymerization solvent and from 35 to 50% of calcium chloride or magnesium chloride. 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

Table 2. Effect of Polymerization Solvent on Polyisoprene Microstmcture...

Commercially, anionic polymerization is limited to three monomers styrene, butadiene, and isoprene [78-79-5], therefore only two useful A—B—A block copolymers, S—B—S and S—I—S, can be produced direcdy. In both cases, the elastomer segments contain double bonds which are reactive and limit the stabhity of the product. To improve stabhity, the polybutadiene mid-segment can be polymerized as a random mixture of two stmctural forms, the 1,4 and 1,2 isomers, by addition of an inert polar material to the polymerization solvent ethers and amines have been suggested for this purpose (46). Upon hydrogenation, these isomers give a copolymer of ethylene and butylene. 

The mid-block monomers are primarily isoprene and butadiene. These diolefins can polymerize in several ways. The isomeric structure of the final polymer has a strong impact on its properties and thermal stability. Isomeric composition is easily varied by changing the polymerization solvent or adding complexing agents. The typical isomeric structures for isoprene and butadiene mid-blocks are shown in Fig. 2. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

Preparation of nanoparticles can be by a variety of different ways. The most important and frequently used is emulsion polymerization others include interfacial polymerization, solvent evaporation, and desolvation of natural proteins. The materials used to prepare nanoparticles are also numerous, but most commonly they are polymers such as poly-alklcyanoacrylate, polymethylmethacrylate, poly-butylcyanoacrylate, or are albumin or gelatin. Distribution patterns of the particles in the body can vary depending on their size, composition, and surface charge [83-85]. In particular, nanoparticles of polycyanoacrylate have been found to accumulate in certain tumors [86,87]. 

Another method of manufacturing polypropylene employs the liquid monomer as the polymerization solvent. This process, known as the liquid propylene or bulk-phase process, has a major advantage over the slurry method in that the concentration of the monomer is extremely high. The high concentration increases the rate of the reaction relative to that seen... 

Propylene polymerization solvent, 50 ml benzene Pqshs, 8 atm temperature, 20°C time, 8 hr. 

In the low catalyst concentration range, polymerization rate is increased with increased amounts of catalyst however, the exact rate dependence on catalyst concentration has not been established. In general, the rate of copolymerization of butadiene with styrene is increased with increased polymerization temperature, increased Ba/Mg mole ratio, increased buta-diene/styrene comonomer feed ratio, and increased dielectric constant of the polymerization solvent. 

Uses Polymerization solvent polymer linking agent organic synthesis. 

W. Schabel, I. Ludwig and M. Kind, Measurements of concentration profiles in polymeric solvent coatings by means of an inverse confocal micro Raman spectrometer - Initial results. Drying Technol., 22, 285-294 (2004). 

Monomers may also be polymerized in solution using good or poor solvents for homogeneous and heterogeneous systems, respectively. In solution polymerizations, solvents with low chain transfer constants are used to minimize reduction in chain length. 

The mobility of the ions in polymer electrolytes is linked to the local segmental mobility of the polymer chains. Significant ionic conductivity in these systems will occur only above the glass transition temperature of the amorphous phase, Tg. Therefore, one of the reqnirements for the polymeric solvent is a low glass-transition temperature for example, Tg = —67°C for PEO. 

Although polymeric solvents have previously been prepared, they are usually based on pyridine, imidazole, or styrene and have the physical forms of a glass or a sticky rubber. Agents in the current application are liquids. Once dissolved poly(2-acrylamido-2-methyl-l-propanesulfonic acid) oxyethylene ammonium salts, however, can be directly converted into fabrics. 

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