Synthesis Optimization and Performance Study of a Reversible <scp> CO ₂ </scp> ‐Responsive Binary Copolymer Based on Tertiary Amine Groups

ABSTRACT To mitigate gas channeling during late‐stage CO 2 flooding, a tertiary amine‐based CO 2 ‐responsive copolymer, P(AM‐DMAPMA), was synthesized via aqueous free‐radical polymerization using acrylamide (AM) as the main monomer and dimethylaminopropyl methacrylamide (DMAPMA) as the functional monomer. Single‐factor experiments identified the optimal synthesis parameters (30 wt% total monomer, 10:7 mass ratio, 0.30 wt% initiator, 60°C, 3 h), yielding a relative molecular mass of 6.8 × 10 6 . FT‐IR and 1 H NMR confirmed the desired structure, while thermal analysis demonstrated robust thermal stability. Rheological tests revealed typical shear‐thinning behavior; initially, a 0.4 wt% solution maintained 36.9 mPa·s at 200 s −1 . Upon CO 2 bubbling, tertiary amine protonation induced a significant viscosity increase to 253.7 mPa·s. Subsequent N 2 bubbling fully recovered its static initial viscosity of 135.2 mPa·s, demonstrating excellent reversibility over multiple CO 2 /N 2 cycles. Furthermore, the protonated 0.4 wt% solution maintained viscosities of 128.5 mPa·s at 60°C and 41.2 mPa·s in 1.0 mol/L NaCl salinity under simulated conditions. Compared with traditional plugging agents, P(AM‐DMAPMA) proves to be a promising candidate for mitigating gas channeling in CO 2 flooding.