CO2-switchable wormlike micelles based on a switchable ionic liquid and tetradecyl trimethyl ammonium bromide

Abstract

CO2-responsive wormlike micelles based on ionic liquid 1,1,3,3-tetramethylguanidine-oleic acid (TMG-OA) and cationic surfactant tetradecyl trimethyl ammonium bromide (TTAB) was designed in this work, avoiding the volatileness and flammability of traditional wormlike micelles formed with amines. It provides a new method of preparing CO2-switchable wormlike micelles based on ionic liquid with acidic group. The ionic liquid TMG-OA was prepared by the direct neutralization reaction between TMG and HOA at the molar ratio of 1:1. Due to the excellent stability and switchability demonstrated by thermogravimetry (TGA) and pH, TMG-OA can be treated as nonvolatile surfactant with CO2-responsive acidic group. Then the worm-based viscoelastic fluid is formed by the electrostatic interaction between TTAB and TMG-OA, and the steady and dynamic rheology show that the viscoelastic fluid has CO2-switchable thinning behavior. The switchable behavior is consistent with the reversible transition of microstructure from wormlike micelles to emulsion, which were detected by the dynamic light scattering (DLS) and cryo-transmission electron microscope (Cryo-TEM). The microstructural transition is induced by the reversible conversation between TMG-OA component and HOA component upon CO2 and N2/heat.