Phase behavior of the ternary aqueous mixtures of two polydisperse ethoxylated nonionic surfactants

Morphologic Properties, Texture Transformations and Optical Refracting Properties: Aqueous Bicomponent Amphiphilic Lyotropic Systems

The mesomorphic, morphologic and optical refracting properties of the bicomponent amphiphilic lyotropic systems have been investigated. Five amphiphiles with various concentration combinations as cationic – cationic, anionic – anionic and cationic – anionic lyotropic mixtures have been used for preparation of lyotropic systems. The mixtures were prepared with a constant (amphiphile1 + amphiphile2)/water concentration ratio. Isotropic lyotropic phase and hexagonal and lamellar lyotropic mesophases have been found in lyotropic systems under investigations. Dynamics of change of the magneto-morphologic properties vs. time, character of the heterophase regions of the mesophase – isotropic liquid phase transitions and temperature dependencies of the optical refracting properties of these bicomponent amphiphilic lyotropic systems have been investigated.

Phase Boundaries, Optical Refraction and Specific Electrical Conductivity Properties in Lyotropic Micellar L1 Phase: Bicomponent Amphiphilic (DDTMABr + HDTMABr) + Water System

In this work, complex investigations of the temperature and concentration behaviour of the optical refraction properties and specific electrical conductivity properties in lyotropic micellar L1 phase have been carried out. Bicomponent amphiphilic (DDTMABr + HDTMABr) + water lyotropic systems with various DDTMABr/HDTMABr concentration ratios have been objects of our investigations. The phase diagram for L1 phase in this system has been determined. Effect of the DDTMABr/HDTMABr concentration ratios on the refractive index and specific electrical conductivity has been observed. The mutual influence of amphiphile with short alkyl chain (DDTMABr) and long alkyl chain (HDTMABr) on the phase states, refractive index and electrical conductivity properties has been found. Our results show that variation of the concentration ratio in a mixture of amphiphiles with different length of the non-polar tail gives possibility to regulate the hydrophilicity degree, optical density, refraction properties and specific electrical conductivity of mixed lyotropic systems.

Structure and dynamics of cetyltrimethylammonium chloride-sodium dodecylsulfate (CTAC-SDS) catanionic vesicles: High-value nano-vehicles from low-cost surfactants

HYPOTHESIS

Catanionic vesicles based on large-scale produced surfactants represent a promising platform for the design of innovative, effective and relatively inexpensive nano-vehicles for a variety of actives. Structural, dynamic and functional behavior of these aggregates is finely tuned by the molecular features of their components and can be opportunely tailored for their applications as drug carriers.

EXPERIMENTS

Here we investigate the aggregates formed by CTAC and SDS, two of the most diffused surfactants, by means of Dynamic Light Scattering, Small Angle Neutron Scattering and Electron Paramagnetic Resonance spectroscopy (EPR). The exploitation of these aggregates as nano-vehicles is explored using the poorly water-soluble antioxidant trans-resveratrol (t-RESV), testing t-RESV solubility and antioxidant activity by means of UV, fluorescence spectroscopy and EPR.

FINDINGS

The presence of a large stability region of catanionic vesicles on the CTAC-rich side of the phase diagram is highlighted and interpreted in terms of the mismatch between the lengths of the surfactant tails and of first reported effects of the chloride counterions. CTAC-SDS vesicles massively solubilize t-RESV, which in catanionic vesicles exerts a potent antioxidant and radical-scavenging activity. This behavior arises from the positioning of the active at the surface of the vesicular aggregates thus being sufficiently exposed to the external medium.

Phase inversion emulsification: Current understanding and applications

This review is addressed to the phase inversion process, which is not only a common, low-energy route to make stable emulsions for a variety of industrial products spanning from food to pharmaceuticals, but can also be an undesired effect in some applications, such as crude oil transportation in pipelines. Two main ways to induce phase inversion are described in the literature, i.e., phase inversion composition (PIC or catastrophic) and phase inversion temperature (PIT or transitional). In the former, starting from one phase (oil or water) with surfactants, the other phase is more or less gradually added until it reverts to the continuous phase. In PIT, phase inversion is driven by a temperature change without varying system composition. Given its industrial relevance and scientific challenge, phase inversion has been the subject of a number of papers in the literature, including extensive reviews. Due to the variety of applications and the complexity of the problem, most of the publications have been focused either on the phase behavior or the interfacial properties or the mixing process of the two phases. Although all these aspects are quite important in studying phase inversion and much progress has been done on this topic, a comprehensive picture is still lacking. In particular, the general mechanisms governing the inversion phenomenon have not been completely elucidated and quantitative predictions of the phase inversion point are limited to specific systems and experimental conditions. Here, we review the different approaches on phase inversion and highlight some related applications, including future and emerging perspectives.

Magnetic particles as liquid carriers in the microfluidic lab-in-tube approach to detect phase change

Magnetic beads (MBs) with ∼1.9 μm average diameter were used to transport specific microliter-scale volumes of liquids between adjacent reservoirs within a closed tube under the influence of a magnetic field. The tube's inner surface is coated with a hydrophobic layer, enabling the formation of a surface tension valve by inserting an air gap between reservoirs. This transfer process was implemented by keeping the MBs stationary with a fixed external magnet while the liquid reservoirs were translated by a computer-controlled syringe pump system. The magnet induces the aggregation of MBs in a loosely packed cluster (void volume ∼90-95%) against the tube's inner wall. The liquid trapped in the MB cluster is transported across the air gap between reservoirs. Fluorescence intensity from a dye placed in one reservoir is used to measure the volume of liquid transferred between reservoirs. The carry-over liquid volume is controlled by the mass of the MBs within the device. The typical volume of liquid carried by the MB cluster is ∼2 to 3 μL/mg of beads, allowing the use of small samples. This technique can be used to study the effect of small compositional variation on the properties of fluid mixtures. The feasibility of this "lab-in-tube" approach for binary phase diagram determination in a water-surfactant (C12E5) system was demonstrated.