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Published 2013 | Published
Journal Article Open

Bubble nucleation in polymer–CO_2 mixtures


We combine density-functional theory with the string method to calculate the minimum free energy path of bubble nucleation in two polymer–CO_2 mixture systems, poly(methyl methacrylate) (PMMA)–CO_2 and polystyrene (PS)–CO_2. Nucleation is initiated by saturating the polymer liquid with high pressure CO_2 and subsequently reducing the pressure to ambient condition. Below a critical temperature (Tc), we find that there is a discontinuous drop in the nucleation barrier as a function of increased initial CO_2 pressure (P0), as a result of an underlying metastable transition from a CO_2-rich-vapor phase to a CO_2-rich-liquid phase. The nucleation barrier is generally higher for PS–CO_2 than for PMMA–CO_2 under the same temperature and pressure conditions, and both higher temperature and higher initial pressure are required to lower the nucleation barrier for PS–CO2 to experimentally relevant ranges. Classical nucleation theory completely fails to capture the structural features of the bubble nucleus and severely underestimates the nucleation barrier.

Additional Information

© 2013 The Royal Society of Chemistry. Received 26th May 2013; Accepted 3rd August 2013. The Dow Chemical Company is acknowledged for funding and for permission to publish the results. The computing facility on which the calculations were performed is supported by an NSFMRI grant, Award no. CHE-1040558.

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August 19, 2023
October 25, 2023