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oai:figshare.com:article/34032151 2026-09-30T12:10:45Z category_1 category_4 category_915 category_7 category_21 category_873 category_46 portal_63 item_type_6 month_year_09_2026

Ethoxy Chain Length Regulated Gemini Polymeric Surfactants for Enhanced Oil Recovery in High-Salinity Reservoirs Zhezhe Cao (24557732) Yu Zhang (12946) Jialin Miao (23770380) Jinlun Yan (25143802) Zi Wang (324031) Longli Zhang (1266822) Biophysics Biochemistry Physical Sciences not elsewhere classified Medicine Biotechnology Chemical Sciences not elsewhere classified Immunology pronounced nonmonotonic dependence oil displacement efficiency forming stable oil molecular dynamics simulations oil displacement performance highest oil recovery 2 +</ sup specific regulation mechanisms eo chain length optimal overall performance molecular association structures tolerant polymeric surfactants sup >+</ sup simulated formation water severe viscosity loss interfacial activity exhibited enhanced oil recovery eo chain interactions induced intermolecular ion 10 </ sub oil recovery molecular association polymeric surfactants specific interactions emulsification performance chain lengths chain entanglement surface activity optimal balance interfacial behavior hydrophobic association tunable ethoxy systematically evaluated salinity reservoirs salinity conditions rheological properties results demonstrated promising strategy gemini surfactant functionalized polymer enhanced heavy In high-salinity reservoirs, conventional polymer flooding systems often suffer from severe viscosity loss, leading to reduced oil recovery efficiency. To address this challenge, a series of Gemini surfactant-functionalized polymer with tunable ethoxy (EO) chain lengths (AASD-O₇, AASD-O₁₀, AASD-O₁₃, and AASD-O₁₅) were synthesized. The influences of EO chain length and ion-specific effects of Na⁺ and Ca²⁺ on rheological properties, interfacial behavior, aggregation characteristics, emulsification performance, and oil displacement efficiency were systematically evaluated. Molecular dynamics simulations were employed to elucidate the effects of EO chain length and salt ions on molecular association, salt tolerance, and oil displacement performance. The results demonstrated that EO chain length played a critical role in regulating the hydrophilic–hydrophobic balance and salt tolerance of the polymeric surfactants. Their viscosity, surface activity, and interfacial activity exhibited a pronounced nonmonotonic dependence on EO chain length, with AASD-O₁₀ showing the optimal overall performance. Under high-salinity conditions, Na⁺ primarily enhanced hydrophobic association and chain entanglement through electrostatic shielding, whereas Ca²⁺ induced intermolecular ion-bridging networks via multipoint coordination with carboxyl groups, resulting in distinct ion-specific regulation mechanisms. Benefiting from the optimal balance between hydrophobic association and EO chain interactions, AASD-O₁₀ maintained excellent interfacial activity in simulated formation water, reducing the oil–water interfacial tension to the order of 10^–3 mN/m and forming stable oil-in-water (O/W) emulsions with a heavy-oil viscosity reduction rate over 99%. Microscopic displacement experiments demonstrated that all AASD polymeric surfactants outperformed conventional partially hydrolyzed polyacrylamide (HPAM), with AASD-O₁₀ achieving the highest oil recovery of 76.67%, which was 22.37 percentage points higher than HPAM. Molecular dynamics simulations further revealed the intrinsic relationships among EO chain length, ion-specific interactions, molecular association structures, and macroscopic oil displacement performance. These findings provide new insights into the design of salt-tolerant polymeric surfactants and offer a promising strategy for enhanced heavy-oil recovery in high-salinity reservoirs. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acs.energyfuels.6c03547.s001 https://figshare.com/articles/journal_contribution/Ethoxy_Chain_Length_Regulated_Gemini_Polymeric_Surfactants_for_Enhanced_Oil_Recovery_in_High-Salinity_Reservoirs/34032151 CC BY-NC 4.0