Vinyl polymerization model

Polyacrylamides are produced commercially in an aqueous environment by free radical polymerization, which follows the classical vinyl polymerization model with initiation, propagation, and termination processes. In this model, the propagation/termination ratio kjk/ and chain transfer to monomer, polymer, initiator, and other small molecules impact the molecular weight of the formed polymer. High-molecular-weight polyacrylamides are possible because of the high ratio for acrylamide and the low chain-... 

Hermans,Jr.,J., Lohr.D., and Ferro,D. Treatment of the Folding and Unfolding of Protein Molecules in Solution According to a Lattic Model. Vol. 9, pp. 229—283. Hutchison, J. and Led with, A. Photoinitiation of Vinyl Polymerization by Aromatic Carbonyl Compounds. Vol. 14, pp. 49—86. 

Figures 4, 5, 6. Comparison between experimental and theoretical conversion histories in emulsion polymerization of methyl methacrylate, styrene, and vinyl acetate. (—), model with gel-effect (—), model without gel-effect.

When the polymerization mechanism is known, peak intensities in the spectra of polymers with different monomer compositions can be compared with calculated intensities based on various polymerization models [e.g., first order Bernoullian (B) or first order Markovian model]. For example, if polymerization mechanism of a vinyl monomer fits a Bernoullian model, then the fractions of triads will be given by ... 

Vinyl polymerization with initiator-transfer reagent-terminator (iniferter) is interesting as a living polymerization model, in which a reversible combination of polymer radicals with stable primary radicals occurs continuously during the polymerization " . The resulting telechelic polymers initiated the polymerization of other monomers to give block copolymers in good yields... 

The kinetics of AN polymerization in solution follows that of the conventional models for ordinary vinyl polymerization as long as the monomer concentration is not too high. It has been shown that at concentrations above 4 M in DMF and 6 M in ethylene carbonate, the monomer acts as a nonsolvent and the mixture becomes heterogeneous. Polymerization rate and molecular mass proceed through a maximum in ethylene carbonate when the AN concentration is raised [648]. 

Typical vinyl polymerizations, for example of ethylene, propylene, vinyl chloride, styrene, and methyl methacrylate, have adiabatic temperature rises between 200 and 1600°C. This leads to the possibility of parametric sensitivity and thermal runaway. Figure 10.2 demonstrates parametric sensitivity for styrene polymerization in a tube that is assumed to be well mixed in the radial direction, as might result from the use of static mixers (that is, the model consists of simultaneous, ordinary differential equations for composition and temperature). The dramatic transition from a controlled reaction to a thermal runaway corresponds to a mere 1 mm difference in tube diameter. Although inlet and wall temperatures can be varied, reaction in a large-diameter tube is not feasible for this and similarly energetic reactions absent an excellent control system [6]. A detailed model of this polymerization in an open tube (the model consists of simultaneous, partial differential equations for composition, temperature, and velocity) shows that hydrody-... 

Boz, E., Ghiviriga, I., Nemeth, A.J. et al. (2008a) Random, defect-free ethylene/vinyl halide model copolymers via condensation polymerization. Macromolecules, 41,25-30. 

Chemistry and Kinetic Model of Radical Vinyl Polymerization... 

It is proposed to polymerize the vinyl group of the hemin molecule with other vinyl comonomers to prepare model compounds to be used in hemoglobin research. Considering hemin and styrene to be species 1 and 2, respectively, use the resonance concept to rank the reactivity ratios rj and X2. 

Other commercially relevant monomers have also been modeled in this study, including acrylates, styrene, and vinyl chloride.55 Symmetrical a,dienes substituted with the appropriate pendant functional group are polymerized via ADMET and utilized to model ethylene-styrene, ethylene-vinyl chloride, and ethylene-methyl acrylate copolymers. Since these models have perfect microstructure repeat units, they are a useful tool to study the effects of the functionality on the physical properties of these industrially important materials. The polymers produced have molecular weights in the range of 20,000-60,000, well within the range necessary to possess similar properties to commercial high-molecular-weight material. 

Our investigations agree with arguments in earlier articles by other authors, namely that empirical reactivity indices provide the best correlation with the goal values of the cationic polymerization (lg krel, DPn, molecular weight). On the other hand, the quantum chemical parameters are often based on such simplified models that quantitative correlations with experimental goal values remain unsatisfactory 84,85>. But HMO calculations for vinyl monomers show, that it is possible to determine intervals of values for quantum chemical parameters which reflect the anionic and cationic polymerizability 72,74) (see part 4.1.1) as well as grades of the reactivity (see part 3.2). 

The literature on the modeling and design of precipitation polymerization reactors is limited primarily to reactor for the bulk polymerization of vinyl chloride (31-38), although other systems have been discussed, particularly in the patent literature (39,40,41). 

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