The Cellulose Nanocrystal Jammed Interfaces Induced by CO2-assisted Self-Assembly for Enhancing Oil Recovery

Stability of displacement front is of great importance in the immiscible fluid displacement for enhancing oil recovery. Here, a CO2-strenghened assembly approach is demonstrated for the fabrication of highly jammed CNSs (cellulose nanocrystal surfactants) with EPD (N '-ethylpropane-1,3-diamine) and TOCNC (TEMPO oxidized cellulose nanocrystal), which produce a structured film at the oil-water interface to counteract the capillary force, and thus governing the local displacing pattern. In this approach, EPD molecules can be deeply protonated in the presence of CO2, favoring their binding forces with TOCNC at the interface to produce more CNSs. Meanwhile, the strong intermolecular attractions among CO2-bearing CNSs promote to form a striped interfacial film with both the close-packed rod-like arrays in horizontal and the multi-layer in lateral. Further, the CNSsbased film confers with a high strength and elasticity can reduce the capillary force by 87 % in microchannels, yielding a smooth water-to-oil displacement front, which markedly enhances the oil recovery by 20.6 % compared to the surfactant-only flooding. This self-assembly strategy has a great implication in ecofriendly and cost-effective applications, such as enhanced oil recovery, CO2 geo-sequestration, and water infiltration.