Modeling of Vinylidene Fluoride Heterogeneous Polymerization in Supercritical Carbon Dioxide

Abstract

The heterogeneous polymerization of vinylidene fluoride in supercritical carbon dioxide has been investigated experimentally, and the obtained results have been interpreted through a detailed kinetic model. The comparison between model predictions and experimental data indicates the presence of two reaction loci: the continuous supercritical phase and the dispersed polymer phase. However, the presence of two reaction loci is not the result of the thermodynamic partitioning between two phases, but rather a kinetic effect. This in fact occurs because part of the radicals generated in the continuous phase, which are driven by thermodynamic equilibrium to diffuse to the dispersed phase, are actually terminated in the former before they can reach the latter. This provides a quantitative explanation for the bimodal molecular weight distributions often measured experimentally for this system.

Modeling of RAFT Copolymerization with Crosslinking of Styrene/Divinylbenzene in Supercritical Carbon Dioxide

“…[30] Comprehensive models allow computation of the full molar mass distribution (for linear cases) by using phase equilibrium, a kinetic description of the reaction and mass transport calculations. [31][32][33][34] On the other hand, simplified models, such as the method of moments, and simple equilibrium calculations have been also used to describe the behavior of these simpler systems. [35][36][37] To the best of our knowledge, the modeling of copolymerization kinetics, molar mass development, and gel fraction evolution for vinyl/divinyl monomers in the presence of RDRP controllers, in scCO 2 , has not been addressed or has been addressed assuming a single phase situation.…”

Polymerization of Vinylidene Difluoride in Supercritical Carbon Dioxide

“…The detailed kinetic analysis of such a precipitation polymerization is a very demanding task, because for each phase rate-and balance equations must be set up for every species present [59,60,62]. This requires at least the knowledge of the distribution of monomer, initiator, radicals and polymer products over the phases.…”

Dispersion copolymerization of acrylonitrile‐vinyl acetate in supercritical carbon dioxide

“…The polymerization rate in the polymer-rich phase initially increases to a maximum value and than slowly decreases with reaction time. 42 There needs a lot of work to find out the reaction mechanism. In all cases, the contents of initiator and acrylonitrile added to the system were kept constant at 1 (w/w% to monomers) and 10 (w/v % in ScCO 2 ) respectively.…”

“…The phenomena are consistent with the reported literature. 13,22,23,29 It is believed that this effect arises from the thermodynamics of mixing, which favors expulsion of CO 2 and monomer from the polymer-rich phase at low CO 2 pressures.…”

“…Among heterogeneous techniques, dispersion polymerization has been proven useful for ScCO 2 -based systems. Since 1994, the successful dispersion polymerizations of methyl methacrylate, [15][16][17][18][19][20] vinylidene fluoride, [21][22] 2-hydroxyethyl methacrylate, 23 styrene, [24][25][26][27] vinyl acetate, 28 acrylonitrile, 29 and vinyl pyrrolidinone 30 in ScCO 2 have been reported. Dispersion polymerizations are governed by a delicate interplay, which includes the separations and interactions of all components.…”