Physicochemical studies on ion-pair amphiphiles: Solution and interfacial behaviour of systems derived from sodium dodecylsulfate and n-alkyltrimethylammonium bromide homologues

Abstract

Bulk and interfacial properties of ion-pair amphiphiles (IPA), formed between sodium dodecylsulfate (SDS) and n-alkyltrimethylammonium bromide homologues (C n TAB; n = 10, 12, 14, 16, and 18), have been investigated. Different phases and aggregated states, formed in the ternary combinations of C n TAB/SDS/H 2 O, have been identified and described. Equimolar mixture of IPAs in water yielded precipitates, in the form of coacervates. Aqueous solubility of isolated coacervates in presence and absence of additives like cholesterol and bile salts have been examined. The isolated coacervates have been characterized by 1 H NMR, FTIR, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and polarization microscopic measurements. The coacervates have appeared in the shape of needle and complex flower-like aggregates. Surface pressure (π)-area (A) isotherm of the coacervates at the air/water interface have been constructed and compared with the lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Morphologies of the IPA monolayers at different surface pressures have been also examined by epifluorescence microscopy. The compressed interfacial monolayers have produced spherical (both regular and irregular) and fern-leaf like domains.

Effect of bovine serum albumin on the functionality and structure of catanionic surfactant at air–buffer interface

“…The C S −1 max values were found to be 30.8, 55.1, 145.5, 35.0 and 30.5 mN m −1 , for C 18 TA + DS − , BSA, DPPC, C 18 TA + DS − -BSA and DPPC-BSA system, respectively. Results suggest that the pure coacervate (C 18 TA + DS − ) was in liquid-expanded state, whereas pure BSA and pure DPPC were in liquid state and liquid-condensed state, respectively [22,23]. The BSA-C 18 TA + DS − and BSA-DPPC systems were in the liquidexpanded state.…”

“…After solvent evaporation, the coacervate was vacuum-dried for 24 h and then stored. 1 H NMR, XRD, FTIR, DSC study, etc., were performed on the formed coacervate to ensure that the results matched with that of reported C 18 TA + DS − [22].…”

“…The formed catanionic coacervate was isolated by repeated partitioning between chloroform-water [22]. After solvent evaporation, the coacervate was vacuum-dried for 24 h and then stored.…”

“…The fluorescent probe was excited at 470 nm with a green emission (530 nm) [22,23]. The images of the compressed films at the desired surface pressure were taken with a digital camera.…”

“…Ionic surfactants could cause major structural changes in the protein conformation with subsequent changes in protein functionality which is not desirable in many applications; the uses of catanionic surfactants are thus preferred over individual components. Recently, catanionic surfactants or coacervates have gained attention of researchers for their structural resemblance to phospholipids [22,23] and their ability to form various aggregated microstructures such as micelles, vesicles, lamellar phases, etc. [24].…”