Homogeneous Solution Polymerizations

Dimethylformamide [68-12-2] (DME) and dimethyl sulfoxide [67-68-5] (DMSO) are the most commonly used commercial organic solvents, although polymerizations ia y-butyrolactoae, ethyleae carboaate, and dimethyl acetamide [127-19-5] (DMAC) are reported ia the hterature. Examples of suitable inorganic salts are aqueous solutioas of ziac chloride and aqueous sodium thiocyanate solutions. The homogeneous solution polymerization of acrylonitrile foUows the conventional kinetic scheme developed for vinyl monomers (12) (see Polymers). 

Development efforts at Celanese Research Co. estabHshed soHd-state polymerization as the most practical process for engineering scale-up. Homogeneous solution polymerization of PBI in polyphosphoric acid was eliminated because of the need to work with low soHd compositions (in the range of 3—5%) during the precipitation, neutralization, and washing steps required for isolation of the product. 

There are two different ways for carrying out polyreactions in a solvent. When both the monomer and the resulting polymer are soluble in the solvent, one speaks of a homogeneous solution polymerization on the other hand, if the polymer precipitates during the course of the reaction, it is called precipitation polymerization. By addition of a solvent, different effects are obtained Basically, the viscosity of the reaction mixture is decreased in comparison to a bulk polyreaction this facilitates heat transfer, mass transport, and handling. 

Thus, it is possible to provide homogeneous solution polymerization systems providing the solubility parameters of the monomer, polymer, and solvent are known. Styrene and maleic anhydride were copolymerized by both techniques in the experiments described in this report. 

Polymer dissolved in solvent None Homogeneous solution polymerization Polymerization of high-density polyethylene in hexane... 

U. S. Agarwal and D. V. Khakhar, Shear flow induced orientation development during homogeneous solution polymerization of rigid rodlike molecules. Macromolecules, 26 (1993) 3960-3965. 

Different processes are nsed in industry for the manufacture of polymers by fi-ee-radical chain polymerization. Among them homogeneous bulk polymerization is economically the most attractive and yields products of higher purity and clarity. But it has problems associated with the heat of polymerization, increases in viscosity, and removal of unreacted monomer. This method is nevertheless used for the manufacture of PVC, polystyrene, and poly(methyl methacrylate). More common processes are homogeneous solution polymerization and heterogeneous suspension polymerization. 

A typical example of the low temperature homogeneous solution polymerization method is the polymerization reaction at room temperature in a nonaqueous polar solvent such as DMAC. ... 

The homogeneous solution polymerization of acrylonitrile follows the conventional kinetic scheme developed for vinyl monomers [36,40,41]. This kinetic scheme can be presented as follows ... 

A typical example of the low-temperature homogeneous solution polymerization method is the... 

Consider a homogeneous solution polymerization occurring in a circular tube. We suppose the flow to be steady, axisymmetric, and Newtonian. The equation of motion for the axial velocity component is ... 

The kinetics of a homogeneous solution polymerization follow the classical kinetics of an addition polymerization reaction, with a new bond being formed between molecules that have not already joined and the reaction proceeding without the elimination of any by-product molecules. Once the reaction has been initiated, the reaction can follow a number of separate stages, which can occur concurrently ... 

Homogeneous Solution Polymerization in Supercritical Carbon Dioxide These polymerizations require that the monomer, the initiator and the polymer remain in solution throughout the reaction. Because carbon dioxide is not a very good solvent for majority of polymers, homogeneous solution polymerizations have been limited to either low conversion operations, or to a few special, mostly fluorinated, monomer/polymer cases that display high solubility in carbon dioxide. A well-known example is the polymerization of 1,1 dihydroperfluorooctyl acrylate (FOA) to from poly(FAO)[3, 17]. 

N-Vinyl-2-pyrrolidone-acrylamide copolymers were prepared by aqueous homogeneous solution polymerization in either distilled water or synthetic seawater. The initial monomer level in the polymerization solutions was either 9.1% or 20% (w/w). The solutions were initiated at either room temperature or 50 C by either 0.50phm or O.lOphm commercial free radical initiators. A temperature controlling water bath was used with the 50 C polymerizations. 

W. Wang, Y. Guo, J.U. Otaigbe, Synthesis and characterization of novel biodegradable and biocompatible poly(ester-urethane) thin films prepared by homogeneous solution polymerization, Polymer 49 (2008) 4393-4398. 

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