Microscopic Mechanism of the Polyacrylamide Hydrophilic Chain on Nanoemulsion-Based Carbon Geological Sequestration

The large emission of greenhouse gases has underscored the critical need for advancing research on carbon capture, utilization, and storage (CCUS) technology. Nanoemulsions have emerged as a promising approach to addressing safety challenges posed by factors such as CO₂ plume migration during carbon geological sequestration. Prolonging the lifetime of nanoemulsions can significantly enhance both the efficiency and the security of carbon storage. The effects of surfactants on supercritical carbon dioxide (sCO₂) nanoemulsions and the sCO₂–H₂O interface are investigated using molecular dynamics simulations. It is revealed that surfactants incorporating trisiloxane hydrophobic groups and polyacrylamide hydrophilic chains exhibited a synergistic interaction, substantially improving the stability of nanoemulsions. Moreover, the acrylamide group is identified as the most significant contributor during the association process among the surfactant components. The PA₅ surfactant reduced the self-aggregation rate to 13.00% and extended the nanoemulsion aggregation time from 11.32 ns (control group without surfactants) to 81.16 ns. The enhancement in stability is attributed to PA₅ achieving an optimal balance between hydrophilicity and CO₂ affinity and binding at the nanoemulsion surface with efficiency and stability. PA₅ holds great promise as a high-performance surfactant for applications in CCUS technology.