Thermo-responsive properties driven by hydrogen bonding in aqueous cationic gemini surfactant systems

Abstract

A series of unexpected thermo-responsive phenomena were discovered in an aqueous solution of the cationic gemini surfactant, 2-hydroxypropyl-1,3-bis(alkyldimethylammonium chloride) (n-3(OH)-n(2Cl), n = 14, 16), in the presence of an inorganic salt. The viscosity change trend for the 14-3(OH)-14(2Cl) system was investigated in the 20-40 °C temperature range. As the temperature increased, the viscosity of the solution first decreased to a minimum point corresponding to 27 °C, and then increased until a maximum was reached, after which the viscosity decreased again. In the 16-3(OH)-16(2Cl) system, the gelling temperature (T(gel)) and viscosity changes upon heating were similar to those in the 14-3(OH)-14(2Cl) system above 27 °C. The reversible conversion of elastic hydrogel to wormlike micelles in the aqueous solution of the 16-3(OH)-16(2Cl) system in the presence of an inorganic salt was observed at relatively low temperatures. Various techniques were used to study and verify the phase-transition processes in these systems, including rheological measurements, cryogenic transmission electron microscopy (cryo-TEM), electric conductivity, and differential scanning calorimetry. The abovementioned phenomena were explained by the formation and destruction of intermolecular hydrogen bonds, and the transition mechanisms of the aggregates were analyzed accordingly.

Insights into the mechanism of high lipid–detergent crystallization of membrane proteins

“…We also observed fingerprint-like patterns [Fig. 3(i)], which resemble previously published images of surfactant micelles (Wei et al, 2016;Yan et al, 2014). However, no intact crystals were observed.…”

Phase Behavior and Aggregation in a Catanionic System Dominated by an Anionic Surfactant Containing a Large Rigid Group

“…The non‐monotonic trend of η 0 is a common phenomenon and can be found in other systems . The sharp enhancement in η 0 can be attributed to the increase in worm‐like micelles induced by adding anionic surfactant, and the decrease may result from micellar branching . The values of η 0max (the maximum of zero‐shear viscosity) are 220.76, 269.48, and 291.51 Pa s for the C 12 ‐MPA‐Na/CTAB, C 14 ‐MPA‐Na/CTAB, and C 16 ‐MPA‐Na/CTAB systems, respectively.…”

“…As Figure b shows, the zero‐shear viscosity ( η 0 ) rapidly increases at first and then decreases with increasing concentration of C n ‐MPA‐Na; the η 0 exhibits a peak for all three systems. The non‐monotonic trend of η 0 is a common phenomenon and can be found in other systems . The sharp enhancement in η 0 can be attributed to the increase in worm‐like micelles induced by adding anionic surfactant, and the decrease may result from micellar branching .…”

“…[4,19,[34][35][36] The sharp enhancement in h 0 can be attributed to the increase in worm-likem icelles induced by addinga nionic surfactant, [17,36] and the decrease mayr esult from micellar branching. [35] Thev alues of h 0max (the maximum of zero-shear viscosity) are 220.76, 269.48, and 291.51 Pa sf or the C 12 -MPA-Na/CTAB, C 14 -MPA-Na/CTAB, and C 16 -MPA-Na/CTAB systems, respectively.T he slight increase in h 0max with increasing alkane chain length demonstrates that the length of the flexible alkyl group could affect the viscosity of the C n -MPA-Na/CTAB systems to ac ertain extent.T he total length of the rigid group and flexible alkyl is more than 18 carbon atoms, so the flexible alkyl chain mayc urve and overlap the extremelyl arge rigid group. [30] The rapid growth of worm-like micelles dependsm ainly on the strongly hydrophobic rigid group.…”

Physicochemical Evaluation of Micellar Solution and Lyotropic Phases Formed by Self-Assembled Aggregates of Morpholinium Geminis

“…Recent reports suggest that the physicochemical and rheological properties of the micellar solution of cationic gemini surfactants containing polar functional groups may be influenced by the affinity of these molecules to form hydrogen bonding with water. 63,64 Such surfactant solution may behave as Newtonian or non-Newtonian fluid depending upon the surfactant concentration and the temperature. Quaternary ammonium gemini surfactants behave as non-Newtonian fluid at higher surfactant concentration because these surfactants self-aggregate in aqueous solution above their cmc values into simple spherical micelles, which generally grow with increasing surfactant concentration and assume different forms such as rodlike micelles or flexible wormlike micelles and so forth.…”