Nanostructured Fluids Based on Propylene Carbonate/Water Mixtures

Abstract

The microstructure of aggregates formed by sodium dodecyl sulfate (SDS) and 1-pentanol in mixtures of water and a polar aprotic solvent (propylene carbonate, PC) was investigated by means of pulsed gradient spin-echo NMR, dynamic light scattering, viscosity, and conductivity measurements. PC partitions itself between micelles and aqueous bulk. The fraction of micellized propylene carbonate remains constant along PC-dilution, and the phase separation takes place when the composition of continuous phase attains the PC/water miscibility gap. The micellized PC is present mainly in the micelle's palisade and strongly increases the total interfacial area, thus acting as a cosurfactant. At high PC content, the system is composed by very small aggregates (around 10 A in radius) made by few SDS molecules (10-6) and PC and pentanol. The resulting system can be described as a nanostructured fluid with a huge interfacial area and a small dispersed phase.

Micellization of amphiphilic block copolymers in binary and ternary solvent mixtures

“…The effect of propylene carbonate and triacetin on the bulk solvent property is less significant. Rather, propylene carbonate and triacetin act by localizing at the PEO-PPO interface and increasing its hydrophobicity (the reports of cmc increase upon propylene carbonate addition for alkyl-containing ionic [57,58] and nonionic surfactants [59] can be interpreted in terms of propylene carbonate rendering the alkyl-water interface relatively less hydrophobic). In contrast, the addition to water of ethanol (with a less negative log P value than water) disfavors micelle formation.…”

“…The influence of the addition to water of the hydrophilic solvents glycerol and glucose on the lyotropic liquid crystal structures of PEO-PPO-PEO block copolymers is different than that of the influence of hydrophobic solvents propylene carbonate and triacetin on the LLC structures [37]. Studies on surfactant micellization in aqueous propylene carbonate mixed solvent support the notion that propylene carbonate acts as a cosurfactant [57,58]. The cmc for sodium dodecyl sulfate (SDS) first decreased, starting from 8 mM in plain water, reached a minimum of 5 mM at about 8 wt% propylene carbonate in water, and then increased to about 20 mM at 18% propylene carbonate in water [58,59].…”

“…Upon further increase in the propylene carbonate concentration, the area per SDS head group increased, with the increased head group repulsion leading to an increase in the cmc. The amount of propylene carbonate (about 40% of the total) that partitioned in the SDS micellar phase remained constant with increasing the propylene carbonate concentration from 0 to about 16 wt% in water [57,58]. The cmc of the nonionic surfactant TX-100 increased from 0.251 to 0.794 mM/kg with increasing the propylene carbonate concentration in aqueous solution from 0 to 18 wt% [59].…”

“…The cmc for sodium dodecyl sulfate (SDS) first decreased, starting from 8 mM in plain water, reached a minimum of 5 mM at about 8 wt% propylene carbonate in water, and then increased to about 20 mM at 18% propylene carbonate in water [58,59]. The added propylene carbonate participated in interface formation (i.e., it adsorbed at the interface) along with SDS, thus increasing the spontaneous curvature of the interface, leading to a transition from initially rod-like micelles, to spherical micelles and as a result the cmc decreased [57]. Upon further increase in the propylene carbonate concentration, the area per SDS head group increased, with the increased head group repulsion leading to an increase in the cmc.…”

The Solvation of Anions in Propylene Carbonate

“…For example, it is possible to obtain sodium, potassium and other alkali metals by electrolysis of their chlorides [10]. PC is used as a co-solvent in cleaning systems to remove naturally aged polymeric acrylic layers from the surface of wall paintings [11,12]. Alkylene carbonates are also used as "safe" solvent substitutes in agriculture and as carrier solvents in therapeutic and cosmetic preparations [13].…”