Properties and mechanism of a poly(ionic liquid) inhibitor contained bi-functional groups for bentonite hydration

Present polymer inhibitors depend on a major inhibitory group to restrain bentonite hydration, and monomer design is concerned to improve the inhibition and stability through complex copolymerization. Conveniently, a homopolymer (PIL-NH₂) that contained primary amine and cationic imidazolium as bi-functional groups was proposed, aiming to provide two synergistic inhibitory modes. Comprehensive methods were conducted to characterize the chemical structure and inhibitory performance of PIL-NH₂. The ζ potential absolute value of bentonite suspension was decreased by PIL-NH₂ from 28.7–33.3 mV to 4–7 mV, and the increment of bentonite particle size d₅₀ was observable from 1.83892 μm to over 200 μm. With water squeezed out, the lattice spacing d₀₀₁ of hydrated bentonite was reduced from 1.9070 to 1.2683 nm due to PIL-NH₂ intercalation. The ESEM images revealed that inhibited bentonite showed a tight structure with classical dehydration phenomenon, and the hydrogen bond between PIL-NH₂ and bentonite was further confirmed according to the FT-IR result. In mechanism analysis, the electrostatic attraction and hydrogen bond existed simultaneously for PIL-NH₂ to adsorb bentonite. The two adsorption modes from bi-functional groups were synergistic to improve inhibition remarkably. PIL-NH₂ maintained high performance during the whole hydration process, including crystalline hydration, osmotic hydration, and hydrated dispersion.