Double-tailed hydrophobically associating polymer: synthesis and enhanced salt resistance properties under external stimuli

The thickening ability of water-soluble polymers is significantly diminished in the presence of metal ions. Here, we successfully developed a novel double-tailed hydrophobic monomer, 2-octyldodecyl methacrylate (ODMA), through a highly efficient one-step esterification process. Subsequently, ODMA was incorporated into hydrophobic association polymer (HAP) via free radical copolymerization with acrylamide (AM) and acrylic acid (AA). The resulting polymers exhibited remarkable salt-responsive rheological properties, with a viscosity of 1035 mPa·s in 150 g/L NaCl solution, significantly higher than that observed in fresh water (440 mPa·s). The viscosity and elasticity were also enhanced under external disturbances in rheological measurements. The phenomena are attributed to the strong hydrophobic interactions by the double tailed hydrophobic structure, which can be observed in the scanning electron microscopy images. This innovative strategy for constructing double-tailed hydrophobic association polymers provides valuable insights and a promising pathway for the rational design of next-generation salt-resistant polymeric materials.