Synergistic Interaction of Short-Chain Phospholipids in the Adsorbed Film and Micelles: Study by Surface Tension and Dilational Viscoelasticity Measurements

Abstract

The aggregate formation and surface adsorption of aqueous binary mixture of short-chain phospholipids, dihexanoyl-phosphatidylcholine (DC6PC), and dioctanoyl-phosphatidylcholine (DC8PC), were examined by surface tension and dilational viscoelasticity measurements. The concentration versus composition diagram of aggregate formation was constructed by analyzing the surface tension data. The diagram demonstrated a synergetic effect that even when the mole fraction of DC8PC in the aqueous solution was 0.02, worm-like micelle was formed and furthermore the addition of DC6PC to DC8PC solution lowered the DC8PC concentration at which worm-like micelle formation starts, although DC6PC molecules do not form worm-like micelles solely. The phase diagram of adsorption was also constructed to elucidate the miscibility of two components in the adsorbed film. The calculated excess Gibbs energy of adsorption was negative, again suggesting a synergistic attractive intermolecular interaction between two species in the adsorbed film. A staggered arrangement was proposed as a favorable intermolecular arrangement. The dilational viscoelasticity was also measured by the electrocapillary wave method, and both storage and loss modulus showed a maximum at around the surface composition of the minimum of the excess Gibbs energy of adsorption.

Investigation of bovine serum albumin-surfactant aggregation and its physicochemical characteristics

“…The steady decrease in the CMC with the increase in the amount of BSA in the mixture supports the formation of mixed aggregates between BSA and surfactant. The break point of the plot of surface tension vs. log [surfactant] provides the values of critical aggregation concentration (CAC) [32]. The CMC values of the surfactants alone are in good agreement with those reported in the literature [33].…”

pH-Dependent Interfacial Tension and Dilatational Modulus Synergism of Oil-Soluble Fatty Acid and Water-Soluble Cationic Surfactants at the Oil/Water Interface

“…This contrasts with publications in which one may identify modulus synergism in binary surfactant systems. In those studies, dilatational moduli synergism could only be identified for either a fixed total concentration ,− or a fixed tension condition, but not both. Modulus synergism may be observed in either the storage modulus, the loss modulus, or perhaps both moduli.…”

“…The binary 2:1 SDS/DTAB mixture at the kerosene/water interface exhibits storage-dominant moduli and a concentration-dependent synergism in both storage and loss moduli. In addition, binary systems exhibiting modulus synergism without tension synergism can also be found, such as SDS with nonionic ethoxylated ether C n EO m surfactants , and some binary mixtures of water-soluble short-chain phospholipids …”

“…In addition, binary systems exhibiting modulus synergism without tension synergism can also be found, such as SDS with nonionic ethoxylated ether C n EO m surfactants 12,32 and some binary mixtures of water-soluble short-chain phospholipids. 13 Some insight into the origin of the storage-dominant dilatational modulus synergism in the PA/TTAB system at pH 7 may be inferred from observations reported by Sumino and co-workers 22,23,33 of a dynamic interfacial "blebbing" deformation process that occurred when a drop of PA-intetradecane solution made contact with an aqueous solution of stearyltrimethylammonium chloride (STAC). This is similar to the binary system investigated here.…”

“…It is of interest to establish a connection between interfacial tension synergism and the conditions that may yield synergistic increases in the magnitudes of the interfacial dilatational moduli. The literature pertaining to interfacial dilatational rheology in surfactant mixtures is limited and thus far is restricted to systems where all the surfactants were dissolved in a single fluid phase. ,− …”