A bile acid-induced aggregation transition and rheological properties in its mixtures with alkyltrimethylammonium hydroxide

Abstract

A bile acid, lithocholic acid (LCA)-induced aggregation transition and rheological properties in the mixtures of LCA and alkyltrimethylammonium hydroxide were investigated. In the salt-free system of tetradecyltrimethylammonium hydroxide (TTAOH) and LCA at equimolar ratio, unilamellar vesicles were observed initially and then transferred to a suspension of tubes within several hours at 25 C, even at a very low total concentration. When an equimolar amount of NaBr was added into the solutions at a higher temperature, huge vesicles with a diameter of tens to hundreds of micrometres were formed initially and crystals quickly emerged inside the vesicles when cooling to room temperature spontaneously. In the longer chain system of cetyltrimethylammonium hydroxide (CTAOH)/LCA, vesicles were also observed after the dissolution of LCA in CTAOH micelle solution, but the vesicles were transferred to helical ribbons after several days at higher concentrations and a lower temperature, and gel was obtained after a longer time of aging. The huge vesicles were more stable than those of the TTAOH/LCA system when an equimolar amount of NaBr was added. The tube suspensions of the TTAOH/LCA system at a high concentration formed a weak gel with relatively low viscoelastic properties, indicating a weak interaction between the aggregates. The tube and helical ribbon suspensions can quickly transfer to viscoelastic vesicular solutions when heated at 30 C, indicating a reversible transition process.

Recent Advances in Catanionic Mixtures

“…They possess a unique molecular structure when compared with typical surfactant molecules, like the steroids, they have a nucleus composed of four fused rings, three cyclohexane rings and one cyclopentane ring as well as hydrophilic hydroxyl groups (Figure 8). Bile acids are favorable compounds for construction of supramolecular structures because of their biocompatibility, high structural rigidity, amphiphilicity and chirality [72]. the hydrophobic and hydrophilic moieties in the surfactants dictates phase behavior of these systems [24].…”

“…Liu et al reported that in lithocholic acid (LCA, Figure 8)/tetradecyltrimethylammonium hydroxide (C 14 TAOH, Figure 4) system transition from vesicles to tubules was observed, while in mixtures of LCA with cetyltrimethylammonium hydroxide (C 16 TAOH), transition from vesicles to helical ribbons occurred [72]. Thus, despite a difference of only two methylene groups in the alkyl chain of C 14 TAOH and C 16 TAOH, morphology of mixed aggregates in these two systems is largely different.…”

“…In addition, it was found that time required for the phase transition depends on alkyl chain length as well. In the C 14 TAOH/LCA systems, the transition from vesicles to tubules was completed within several hours, while in the C 16 TAOH/ LCA system, the vesicles were converted to helical ribbons after more than 4 days, depending on the concentration and temperature [72].…”

Self-aggregation mechanism of a naphthylamide cationic derivative of cholic acid. From fibers to tubules

“…34 Manna et al 35 have studied catanionic mixtures formed by long chain alkyltrimethylammonium bromides (C n TABr, n ¼ 12, 14 and 16) in combination with sodium cholate (NaC) and sodium deoxycholate (NaDC). Liu et al 36 have observed that the free-salt catanionic mixture of lithocholate with tetradecyl-and cetyl-trimethylammonium hydroxides form unilamellar vesicles. In the second case, vesicles were transferred to helical ribbons aer several days.…”

Tuning and controlling the shape of mesoporous silica particles with CTAB/sodium deoxycholate catanionic mixtures

“…The interaction between the two surfactants and the properties of the resulting aggregates depend not only on the type of BS but also on the ratio between the oppositely charged surfactants. [46][47][48][49][50][51][52][53][54][55] Herein we report a detailed investigation on the effect of CTAB/bile salt catanionic mixtures when employed at different ratios. In particular, we employ sodium deoxycholate (NaDC, Fig.…”