Polymerization kinetics quantitative

Paczkowski J, Neckers DC (1991) Twisted intramolecular charge-transfer phenomenon as a quantitative probe of polymerization kinetics. Macromolecules 24(10) 3013-3016... 

Any study of the polymerization kinetics of a bisbenzocyclobutene monomer is complicated by the lack of understanding of the resulting polymer s structure and the fact that as the polymerization proceeds, the reaction mixture crosslinks and vitrifies. This vitrification limits somewhat the number of quantitative methods which can be used to study the bisbenzocyclobutene polymerization kinetics. Some techniques are however useful under these constraints and good kinetic results have been obtained by both infrared and thermal analysis methods. 

The polymerization kinetics of the bisbenzocyclobutene diketone monomer 14 (Fig. 10) were studied in the melt at various temperatures by infrared spectroscopy [48]. This technique has the advantage that it is relatively insensitive to the physical state of the system as it proceeds from monomer melt through the gel point and into the vitreous state. In addition, quantitative... 

Continuous emulsion polymerization processes are presently employed for large scale production of synthetic rubber latexes. Owing to the recent growth of the market for polymers in latex form, this process is becoming more and more important also in the production of a number of other synthetic latexes, and hence, the necessity of the knowledge of continuous emulsion polymerization kinetics has recently increased. Nevertheless/ the study of continuous emulsion polymerization kinetics hasf to datef received comparatively scant attention in contrast to batch kinetics/ and very little published work is available at present/ especially as to the reactor optimization of continuous emulsion polymerization processes. For the theoretical optimization of continuous emulsion polymerization reactors/ it is desirable to understand the kinetics of emulsion polymerization as deeply and quantitatively as possible. 

It appears that the reaction mechanism and the intermediates involved in the solid-state polymerization of diacetylenes are reasonably well understood. However, experimental results obtained with special monomers should not be generalized. It is not possible to design a monomer with desired properties. Inspection of Table 1 shows that on the basis of the crystallographic data and the monomer packing the absolute reactivity and the polymerization kinetics caimot be quantitatively predicted, e.g. it is not possible, to date, to explain why certain diacetylenes can be polymerized thermally whereas others with equal packing are thermally inactive. A more realistic kinetic model should include the various energy transport processes and the complex side group motions which are connected to the reaction. 

Quantitative theoretical treatment of emulsion polymerization kinetics... 

The low-temperature polymerization of a-methylstyrene initiated by Bu"OTiCl3 has been looked at in some detail by Sigwalt and his co-workers. Under dry conditions only small conversions are obtained in contrast to the quantitative yields with TiCU. In the latter case it can be argued that the Lewis acid is sufficiently strong to allow direct initiation, whereas with the weaker Bu"OTiCl3 this mechanism might not contribute to such an extent. However, addition of small amounts of water and HCl to the latter system produces fast polymerizations with quantitative yields, and the various kinetic parameters for the reaction have been evaluated. 

The kinetics of emulsion polymerization is complex, involving a large number of species and at least two phases. The first quantitative approach to emulsion polymerization kinetics led to extensions by many others.The important events to consider are 1) the free-radical reactions of chain formation initiation, propagation, chain transfer, and termination and 2) the phase transfer events that control particle formation radical entry into particles from the aqueous phase, radical exit into the aqueous phase, radical entry into micelles, and the aqueous phase coil-globule transition. In free-radical emulsion polymerization, the fundamental steps are shown schematically in Fig. 1... 

More recently, quantitative treatments of plasma polymerization kinetics have become available. 

In the above cases, the polymerization kinetics are so simple that it is useful to classify ionic polymerization kinetics according to whether the initiators are quantitatively and instantaneously dissociated or not. (It should be noted that the term dissociation does not denote any special kind of charge separation. Probably one has to regard this dissociation as a separation of ion pairs by solvent molecules, but not a separation in the sense of forming single ions which can move independently from the counterion.)... 

Since the polymerization kinetics in the above cases are extremely simple, ionic polymerization kinetics can be conveniently classified according to whether the initiators are quantitatively and instantaneously dissociated or not. 

Many of the results of wartime research in the USA are reviewed by Harkins [43,50,51]. The quantitative development of the Harkins theory which still dominates most discussions of emulsion polymerization kinetics was published by Smith and Ewart in 1948 [52] with a first attempt at experimental verification by Smith [53]. 

If it is known that this hypothesis is an oversimpMfication, then why is it made so often Mostly, because the additional effort required to integrate micro-, meso- and macroscale phenomena in a single model does not necessarily lead to better quantitative predictions when it comes to industrial reactors. Uncertainties on model parameter values are, most often, too high to try to decouple true polymerization kinetic parameters from mass and heat transfer effects often apparent kinetic parameters will do an equally good job from an engineering perspective [86]. 

Maleic anhydride was used as the dienophile, allowing for further functionalization following the assembly of the norbornene skeleton. Diels-Alder cycloadditions of the above-mentioned fiilvene derivatives with maleic anhydride at elevated temperatures, between 80 °C and 120 °C, and moderate concentrations, 0.2 to 0.5 M, afforded quantitative yields of the corresponding norbornene derivatives 5, 7, and anhydride precursor of 9 (see Table I) (29). At total adduct concentrations above 1.5 M or temperatures above 130 °C, a solid oligomeric side product, presumably a copolymer of the reactants, was obtained. Two isomers, endo or exo, can be obtained from cycloaddition reactions, depending on the nature of adducts or the reaction temperature. These isomers exhibit different polymerization kinetics, where, in most cases, endo adducts polymerize very slowly, and result in low conversions. 

The quantitative description of particle nucleation is perhaps the most difficult problem of emulsion polymerization kinetics. Equation 5 is the well known relationship derived by Smith and Ewart (10) for their Case 2 Model. 

Syndiotactic polystyrene (SPS) can be readily polymerized using homogeneous or heterogeneous metallocene catalysts, based on group 4 metal compounds, especially titanium compounds like T1CI4, CpTiClj, and Cp Ti(OCH3)3 with methyl aluminoxane (MAO) as cocatalyst [1-3]. The recent developments of transition metal catalysts and reaction mechanisms are discussed in earlier chapters. This chapter will be focused on the quantitative aspects of SPS polymerization kinetics and related physical and chemical phenomena. 

Every known quantitative study of polymerization is surveyed in Part 11 of this volume. It seems that the 1930s was one of the great ages of the detailed study of polymerization kinetics. 

The first quantitative model, which appeared in 1971, also accounted for possible charge-transfer complex formation (45). Deviation from the terminal model for bulk polymerization was shown to be due to antepenultimate effects (46). Mote recent work with numerical computation and C-nmr spectroscopy data on SAN sequence distributions indicates that the penultimate model is the most appropriate for bulk SAN copolymerization (47,48). A kinetic model for azeotropic SAN copolymerization in toluene has been developed that successfully predicts conversion, rate, and average molecular weight for conversions up to 50% (49). 

The kinetic mechanism of emulsion polymerization was developed by Smith and Ewart [10]. The quantitative treatment of this mechanism was made by using Har-kin s Micellar Theory [18,19]. By means of quantitative treatment, the researchers obtained an expression in which the particle number was expressed as a function of emulsifier concentration, initiation, and polymerization rates. This expression was derived for the systems including the monomers with low water solubility and partly solubilized within the micelles formed by emulsifiers having low critical micelle concentration (CMC) values [10]. 

Recent kinetic studies of this polymerization 14) revealed that some parasitic reactions cause termination and induction periods in the overall process. Their nature is not known yet. It is tentatively suggested that the activated polymers react with the dormant ones yielding some destruction products, although the nucleophile capable of activating the still available dormant chains is regenerated. Alternatively it is possible that the intermediate 3 is labile and may decompose before collapsing into 4 with regeneration of the nucleophile. Whatever the cause of these side reactions, one should stress that the conversion of the monomer into polymer is almost quantitative. 

The semibatch model GASPP is consistent with most of the data published by Wisseroth on gas phase propylene polymerization. The data are too scattered to make quantitative statements about the model discrepancies. There are essentially three catalysts used in his tests. These BASF catalysts are characterized by the parameters listed in Table I. The high solubles for BASF are expected at 80 C and without modifiers in the recipe. The fact that the BASF catalyst parameters are so similar to those evaluated earlier in slurry systems lends credence to the kinetic model. 

On the other hand, the macrolides showed unusual enzymatic reactivity. Lipase PF-catalyzed polymerization of the macrolides proceeded much faster than that of 8-CL. The lipase-catalyzed polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics. For all monomers, linearity was observed in the Hanes-Woolf plot, indicating that the polymerization followed Michaehs-Menten kinetics. The V, (iaotone) and K,ax(iaotone)/ m(iaotone) values increased with the ring size of lactone, whereas the A (iactone) values scarcely changed. These data imply that the enzymatic polymerizability increased as a function of the ring size, and the large enzymatic polymerizability is governed mainly by the reachon rate hut not to the binding abilities, i.e., the reaction process of... 

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