Study on the Strong Association and Synergistic Temperature and Salt Resistance Mechanism of Differential Charge Surfactants and Ionic Polymer Systems

Abstract

ABSTRACT The amphiphilic hydrophobic associative polyacrylamide (HAPAM) was synthesized via free radical copolymerization using hexadecyl allyl dimethyl ammonium chloride (C16DMAAC), acrylic acid (AA), acrylamide (AM), and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) as raw materials. Additionally, the oil amide sulfobetaine (OSB) amphoteric surfactant was synthesized from oil amide dimethyl tertiary amine, sodium sulfite (NaHSO 3 ), and epichlorohydrin. The impact of various charged surfactants (SDS, DTAB, OSB, and AEO) on the binding properties of HAPAM in NaCl solution was investigated through measurements of apparen t viscosity, dynamic light scattering, cryogenic scanning electron microscopy, and rheological analysis. The results indicated that the viscosity of HAPAM in NaCl solution exhibited a parabolic relationship, first rising and then falling, with increasing concentrations of SDS and OSB. Upon the addition of OSB, the temperature and shear resistance of the polymer system were significantly enhanced. Compared to the system before surfactant addition, the maximum viscosity increased by approximately 10 mPa (70%) after shearing at 120°C. At different concentrations of OSB and SDS, the viscosity increased by 133%–157%, the hydration radius of HAPAM expanded by 2.28 to 6.22 times, and the absolute value of the zeta potential increased by 27.66 mV. Microscopic morphological observations revealed that the polymer system formed a three‐dimensional network structure of intermolecular association with the addition of surfactants, ultimately creating a dense spatial structure. However, this phenomenon was not as pronounced for cationic and nonionic surfactants. These findings, corroborated by molecular dynamics simulations, confirmed that an appropriate amount of anionic surfactants can enhance hydrophobic binding, expand electrostatic repulsion between anions, and significantly improve the resistance and electrostatic shielding effect of HAPAM against salt solution compression bilayer. This study provides valuable insights into the effects of surfactants on the cross‐linking structure and binding properties of HAPAM in NaCl solution, offering guidance for improving the recovery rate in binary composite flooding applications.