Viscoelastic Fluid Formed by Ultralong-Chain Erucic Acid-Base Ionic Liquid Surfactant Responds to Acid/Alkaline, CO2, and Light.

As a leftover of grease processing, the efficient utilization of erucic acid is still a challenge. An alternative strategy is to develop erucic acid-derived surfactants. However, erucic acid-based ionic liquid surfactants were barely involved. Here, a novel ionic liquid surfactant, benzyltrimethylammonium erucate (ErBTA), was developed by a simple neutralization reaction, and its aggregations in the diluted and concentrated solution were systematically studied by surface tension, conductivity, rheology, and cryo-TEM techniques. The results showed that ErBTA has a very low metaling point (-7.03 °C) and possesses excellent water solubility (Krafft temperature <4 °C). ErBTA alone starts to form micelles at a very low concentration (0.028 mmol/L) and then to form worm-based viscoelastic fluid at 4.07 mmol/L without any additives, exhibiting excellent self-assembly ability and thickening ability. This viscoelastic fluid formed by ErBTA can simultaneously respond to three stimuli: common acid/alkaline, CO2 gas, and light, accompanied by an interesting gel-sol conversion, reflecting microstructure transition from wormlike micelles to spherical micelles. Although in essence CO2 and light also act as pH regulators in the current system, they provide more sophisticated approaches to tune pH. Such a viscoelastic fluid with the characteristics of easy availability, renewability of raw materials, the simplicity of fabrication, good water-solubility, and excellent thickening ability may be an attractive candidate for clean fracturing in oil/gas recovery and fluid drag reduction.