Highly Deformable Nano-Cross-Linker-Bridged Nanocomposite Hydrogels for Water Management of Oil Recovery

Conventional poly­(acrylamide) (PAM)-based hydrogels suffered from mechanical instability during water flooding, which markedly reduced their performance for water management and oil recovery. In this report, divinylbenzene (DVB) nanostructured cross-linker-bridged nanocomposite hydrogels with high elasticity were described to increase hydrogel mechanical integrity. Precipitation polymerization of DVB monomers generated well-defined DVB nano-cross-linkers having styrenyl moieties on the surfaces, as demonstrated by proton nuclear magnetic resonance analysis. Frequency sweeps of the hydrogels confirmed the formation of covalent junctions between PAM chains and DVB nano-cross-linkers within the network. The nanocomposite hydrogels with covalent cross-links showed a high degree of extensibility, greater than 40 times compared to self-cross-linked <i>N</i>,<i>N</i>′-dimethylacrylamide hydrogels with elongation of 14 and <i>N</i>,<i>N</i>′-methylenebis­(acrylamide) cross-linked PAM hydrogel having stretchability less than 2 times. The concentration of ammonium persulfate initiator showed a greater effect on mechanical robustness than DVB nano-cross-linkers. The increase in the initiator significantly increased hydrogel extensibility upon stress. In addition, nano-cross-linker-based hydrogel displayed slow swelling kinetics in brine in comparison to commercially available LiquiBlock 40K gel. Low-cost DVB monomer-based nano-cross-linker-bridged highly deformable hydrogels with excellent elasticity rendered hydrogel production in industrial-scale feasible. High deformation characteristics facilitated hydrogel propagation through pore throats for in-depth fluid diversion