Interactions of Carbon Dioxide with Polymers and Monomers

Interactions of Carbon Dioxide with Polymers and Monomers 

For application of supercritical CO2 as a medium in polymer processes, it is important to consider its interactions with polymers and monomers. In general, the thermodynamic properties of pure substances and mixtures of molecules are determined by intermolecular forces acting between the molecules or polymer segments. By examining these potentials between molecules in a mixture, insight into the solution behavior of the mixture can be obtained. The most commonly occurring interactions are dispersion, dipole-dipole, dipole-quadru-pole, and quadrupole-quadrupole (Fig. 1.8). 

The solvent strength of carbon dioxide for solutes is dominated by low polarizability and a strong quadrupole moment (Table 1.3). Consequently, carbon dioxide is difficult to compare to conventional solvents because of this ambivalent character. With its low polarizabihty and nonpolarity, carbon dioxide is similar to perfluoromethane, perfluoroethane, and methane. 

The interaction of CO2 and polymers can be divided into three application areas processing of swollen or dissolved polymers and applications where carbon dioxide does not interact with the polymer. An extensive review on polymer processing using supercritical fluids has been written by Kazarian [55], including possible applications based on the specific interaction of CO2 and the polymer system involved. 

Another important requirement for the development of new polymer processes based on SCCO2 is knowledge about the phase behavior of the mixture involved, which enables the process variables to be tuned properly to achieve maximum process efficiency. Determining parameters in the phase behavior of a system are the solvent quality, the molecular weight, chain branching, and chemical architecture of the polymer, as well as the effect of endgroups and the addition of a cosolvent or an antisolvent An overview of the available literature on the phase behavior of polymers in supercritical fluids has been published by Kirby and McHugh [50]. 

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Interactions of Carbon Dioxide with Polymers and Monomers I 9... 

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