Understanding the mechanism of the CO2 responsive viscoelastic fluids obtained from cetyltrimethylammonium bromide, sodium salicylate and N, N-dimethylcyclohexylamine

Highlights: • DMCA was found to be protonated into quaternary ammonium salt, and thus converted to water soluble species. • With addition of DMCA, the system transforms from gel-like fluid to water-like system, and subsequently self-assemble to form viscoelastic fluid after spraying of CO_2. • The micelle structures, molecular states and intermolecular interactions were exploited to achieve at the most plausible mechanism associated to the transformation. A viscoelastic fluid, composing of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) at a mole ratio of 0.75 has been synthesized in the present investigation along with the incorporation of N, N-dimethylcyclohexylamine (DMCA) to endow CO₂ responsive property into it. In present of CO₂, DMCA was found to be protonated into quaternary ammonium salt, and thus converted to water soluble species. With addition of DMCA, the system transforms from gel-like fluid to water-like system, and subsequently self-assemble to form viscoelastic fluid after spraying of CO₂. The rheological measurements and cryo-transmission electron microscopic (Cryo-TEM) characterization revealed that, the sol–gel transition was associated with the spherical-wormlike miceller transformation. This transformation was found to be reversible in nature. The micelle structures, molecular states and intermolecular interactions were exploited to achieve at the most plausible mechanism associated to the transformation.