Heterogeneous Polymerization in Supercritical Carbon Dioxide

Philipp A. Mueller, Barbara Bonauoglia, Giuseppe Storti, and Massimo Morbidelli 

In this chapter, the main features of heterogeneous polymerization in scC02 are analyzed. After a critical review of the main contributions in the literature, a comprehensive mathematical model is proposed. Finally, two case studies, selected as representative of dispersion and precipitation process, respectively, are discussed with the aim of elucidating the main mechanisms of the two heterogeneous processes. 

Supercritical Carbon Dioxide in Polymer Reaction Engineering 

Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 

To represent dispersion polymerization in conventional liquid media, several models have been reported in the literature, mainly focused on the particle formation and growth [33, 34] or on the reaction kinetics. Since our first aim is the reliable description of the reaction kinetics, we focus on the second type of models only. The model developed by Ahmed and Poehlein [35, 36], applied to the dispersion polymerization of styrene in ethanol, was probably the first one from which the polymerization rates in the two reaction loci have been calculated. A more comprehensive model was later reported by Saenz and Asua [37] for the dispersion copolymerization of styrene and butyl acrylate in ethanol-water medium. The particle growth as well as the entire MWD were predicted, once more evaluating the reaction rates in both phases and accounting for an irreversible radical mass transport from the continuous to the dispersed phase. Finally, a further model predicting conversion, particle number, and particle size distribution was proposed by Araujo and Pinto [38] for the dispersion polymerization of styrene in ethanol. 

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Professor DeSimone, is the pioneer of heterogeneous polymerizations in supercritical carbon dioxide. 

I 6 Heterogeneous Polymerization in Supercritical Carbon Dioxide Table 6.3 (continued)... 

In this chapter, a comprehensive model of heterogeneous polymerization in supercritical carbon dioxide has been applied to two different systems, with the aim of elucidating the key mechanisms underlying the process. The main mod-... 

Singley, E.J. Development of fluoroether amphiphiles and their applications in heterogeneous polymerizations in supercritical carbon dioxide, PhD thesis, Univ. of Pittsburgh 1997. 

Kennedy, K. A., Roberts, G. W. and DeSimone, J. M. Heterogeneous Polymerization of Fluo-roolefins in Supercritical Carbon Dioxide. Vol. 175, pp. 329-346. 

Cooper, A. I. Hems, W. P. Holmes, A. B. Synthesis of Highly Cross-Linked Polymers in Supercritical Carbon Dioxide by Heterogeneous Polymerization. 

Heterogeneous Polymerization of Fluoroolefins in Supercritical Carbon Dioxide... 

Heterogeneous Polymerization of Fluoroolefins in Supercritical Carbon Dioxide 331 Table 1 Critical temperatures and pressures of substances useful as supercritical fluids [9]... 

In this special volume on polymer particles, recent trends and developments in the synthesis of nano- to micron-sized polymer particles by radical polymerization of vinyl monomers in environmentally friendly heterogeneous aqueous and supercritical carbon dioxide fluid media are reviewed by prominent worldwide researchers. Polymer particles are prepared extensively as synthetic emulsions and latexes, which are applied as binders in the industrial fields of paint, paper and inks, and films such as adhesives and coating materials. Considerable attention has recently been directed towards aqueous dispersed systems due to the increased awareness of environmental issues. Moreover, such polymer particles have already been applied to more advanced fields such as bio-, information, and electronic technologies. In addition to the obvious commercial importance of these techniques, it is of fundamental scientific interest to completely elucidate the mechanistic details of macromolecule synthesis in the microreactors that the polymer particles in these heterogeneous systems constitute. 

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