CO ₂ Viscosification by Polyolefin for Safe and Efficient Sequestration in Saline Aquifers: Molecular Insights from Solubilization–Viscosification–Adsorption Performance

Direct viscosification of CO2 has shown potential for improvements in the storage of CO2 in saline aquifers. However, the molecular-scale mechanisms governing the performance of viscosifiers in supercritical CO2 have been inadequately explored. This study addresses this gap through an extensive molecular dynamics simulation. We systematically investigate six commercial oligomers, including 1 fluorinated oligomer (i.e., PFOA), 1 siloxane-based oligomer (i.e., PDMS), 2 ether-containing hydrocarbon-based oligomers (i.e., PBVE, PVEE), 1 ester-containing hydrocarbon-based oligomer (i.e., PVAc), and polyolefin (i.e., P1D). Our multistep density functional theory and molecular dynamics simulation workflow, validated against experiments, probes atomistic interactions to establish structure–property relationships, revealing how specific functional groups govern CO2-philicity, viscosification efficiency, and adsorption behavior, linking molecular structure to macroscopic performance. It reveals that polyolefins (i.e., P1D), achieve optimal performances in three aspects. P1D’s methyl groups provide effective van der Waals interactions with CO2, enabling moderate solubilization (Δδ = 0.13) and viscosity enhancement (ηr = 1.52), while its nonpolar nature ensures minimal quartz adsorption (−18.2 kcal/mol). In contrast, fluorinated and oxygenated oligomers suffer from significant adsorption and thermal degradation. Crucially, the singly dispersed state of the P1D provides exceptional thermal stability (ηr retention >90% at 358 K). This systematic molecular-level analysis, underpinned by substantial simulation data, establishes polyolefins as potential viscosifiers, providing key insights for safe and efficient CO2 sequestration.