Study on Microphase Separation of Waterborne Polyurethane by the Infrared Spectroscopy Peak Fitting

The structure of CO2 and CH4 at the interface of a poly(urethane urea) oligomer model from the microscopic point of view

The world desperately needs new technologies and solutions for gas capture and separation. To make this possible, molecular modeling is applied here to investigate the structural, thermodynamic, and dynamical properties of a model for the poly(urethane urea) (PUU) oligomer model to selectively capture CO₂ in the presence of CH₄. In this work, we applied a well-known approach to derive atomic partial charges for atoms in a polymer chain based on self-consistent sampling using quantum chemistry and stochastic dynamics. The interactions of the gases with the PUU model were studied in a pure gas based system as well as in a gas mixture. A detailed structure characterization revealed high interaction of CO₂ molecules with the hard segments of the PUU. Therefore, the structural and energy properties explain the reasons for the greater CO₂ sorption than CH₄. We find that the CO₂ sorption is higher than the CH₄ with a selectivity of 7.5 at 298 K for the gas mixture. We characterized the Gibbs dividing surface for each system, and the CO₂ is confined for a long time at the gas-oligomer model interface. The simulated oligomer model showed performance above the 2008 Robeson's upper bound and may be a potential material for CO₂/CH₄ separation. Further computational and experimental studies are needed to evaluate the material.