Atomistic modeling of the interaction of CO2 with bisphenol-A polycarbonate

Molecular modeling techniques were used to study the sorption and diffusion of carbon dioxide in bisphenol-A polycarbonate (BPAPC) at an atomistic level. These calculations were used to compute the heat of solution of carbon dioxide in the amorphous polymer. Sorption calculations included contributions from: (a) the favorable interaction of carbon dioxide with the polymer, and (b) the unfavorable process of creating a void of sufficient size to accommodate the carbon dioxide molecule. Six unique model structures were created to provide a statistical sample, and calculations were performed using the Biosym Technologies Insight/Discover software tools. An average value of -6.1 kcal mol(-1) was calculated for the heat of solution for the six structures, with large deviations among the results of the individual calculations. The heat of solution of carbon dioxide in BPAPC has been reported in the literature as -5.3 kcal mol(-1). The agreement between the calculated and experimental heat of solution of carbon dioxide in BPAPC indicates that the methodology may be extended to other gases and polymer systems with appropriate refinement. Calculated values of the heat of solution can be used with entropy data to predict the gas solubility coefficient. Such a predictive ability has applications in continuing research on gas barrier and membrane materials, polymeric foams, removal of unreacted monomer from polymeric materials, and plasticizer sorption/desorption.