(315c) Specific Interactions in CO2 + Polymer Systems

It is well known that polymer solubility in CO2 can be enhanced by the incorporation of carbonyl, silicone, or fluorine groups that exhibit specific interactions with CO2. More recently, nanoporous polymers for the storage of H2 and CO2 have been prepared by CO2 foaming in localized nanocells within CO2-philic domains. Knowledge of specific interactions between CO2 and CO2-philic groups is essential in the design of these nanoporous polymers. We have developed a compressible lattice model for representation of phase equilibria in CO2 + polymer systems in which specific interactions play an important role in determining phase equilibria. The model explicitly accounts for weak complex formation in these systems, using two parameters that can be obtained from Fourier transform infrared spectroscopy measurements or by correlation of experimental phase equilibrium data. We have compared our quantified specific interactions with quantum calculations. Furthermore, we show that our model can be used in both low-pressure and high-pressure systems, and is also able to predict glass transition temperatures in polymers swollen by CO2. This ability has allowed us to fabricate nanoporous polymeric materials using supercritical CO2 as a blowing agent.