Liquid-liquid phase separated microdomains of an amphiphilic graft copolymer in a surfactant-rich medium

The liquid-liquid phase separation (LLPS) of amphiphilic thermoresponsive copolymers can lead to the formation of micron-sized domains, known as simple coacervates. Due to their potential to confine active principles, these copolymer-rich droplets have gained interest as encapsulating agents. Understanding and controlling the conditions inducing this LLPS is therefore essential for applicative purposes and requires thorough fundamental studies on self-coacervation. In this work, we investigate the LLPS of a comb-like graft copolymer (PEG-g-PVAc) consisting of a poly(ethylene glycol) backbone (6 kDa) with ∼2-3 grafted poly(vinyl acetate) chains, and a PEG/PVAc weight ratio of 40/60. Specifically, we report the effect of various water-soluble additives on its phase separation behavior. Kosmotropes and non-ionic surfactants were found to decrease the phase separation temperature of the copolymer, while chaotropes and, above all, ionic surfactants increased it. We then focus on the phase behavior of PEG-g-PVAc in the presence of sodium citrate and a C_14-15 E₇ non-ionic surfactant (N45-7), defining the compositional range for the generation of LLPS microdomains at room temperature and monitoring their formation with fluorescence confocal microscopy. Finally, we determine the composition of the microdomains through confocal Raman microscopy, demonstrating the presence of PEG-g-PVAc, N45-7, and water. These results expand our knowledge on polymeric self-coacervation, clarifying the optimal conditions and composition needed to obtain LLPS microdomains with encapsulation potential at room temperature in surfactant-rich formulations.

Alcohols Effect on Critic Micelle Concentration of Polysorbate 20 and Cetyl Trimethyl Ammonium Bromine Mixed Solutions

In this research, the micellar behavior of a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB) and an nonionic surfactant, polysorbate 20 (Polyoxyethylene (20) sorbitan monolaurate) in different alcohol solutions media was investigated over the temperature range 293.15-313.15 K. The interaction between two surfactants in binary systems can be determined by calculating the values of their β parameters. The critical micelle concentrations (CMC) of the micelles were determined from the surface tension, the conductivity at different temperatures. The CMC behavior of CTAB and polysorbate 20 was analyzed in terms of the effect of temperature and the increase in the alcohol carbon chain. Changes in the critical micelle concentration of mixed surfactant systems of different alcohol solutions were measured. The CMC decreased sharply as the hydrocarbon chain length of the alcohols becomes larger. This shows that the more hydrophobic alcohols are, the more marked a decrease in CMC is observed.

Extraction of Copper(II) from Sulphate Aqueous Medium with N,N′-bis(2-hydroxy-1-naphthalideneaminoethyl)amine Polydentate Schiff Base in Aqueous Two-phase Micellar of Non-Ionic Surfactant

The present paper outlines the use of the novel polydentate Schiff's base extractant, N,N′-bis(2-hydroxy-1-naphthalideneaminoethyl)amine (H2L), for copper(II) extraction in aqueous two-phase micellar of non-ionic surfactant from sulphate media. The extraction process is based on the formation of the hydrophobic complex of copper(II)-H2L, which is subsequently extracted into the non-ionic surfactant-rich phase of p-octylpolyethyleneglycolphenylether (Triton X-100) at a temperature above the cloud point temperature (CPT). The phase diagrams of the binary system, water-surfactant (Triton X-100), and of the ternary systems, water-surfactant-salt (Na2SO4), were examined. The effects of the main experimental parameters such as pH, extractant concentration and non-ionic surfactant concentration on the extraction process of copper(II) were studied. The extraction yield was found to be significantly depending on the aqueous solution pH. Copper(II) was extracted with H2L and Triton X-100 in the pH range of (3–12). From the equilibrium slope analysis method, it was suggested that the stoichiometry of the extracted complexes have a composition of 1:1 (Cu:H2L). The optimum conditions of the extraction of copper(II) have been established as the following: (1) 2 × 10−3 M extractant; (2) 5% (m/v) surfactant; (3) pH of 7.2; (4) 7% (m/v) Na2SO4 and (5) temperature of 65°C.

Clouding behaviour in surfactant systems

A study on the phenomenon of clouding and the applications of cloud point technology has been thoroughly discussed. The phase behaviour of clouding and various methods adopted for the determination of cloud point of various surfactant systems have been elucidated. The systems containing anionic, cationic, nonionic surfactants as well as microemulsions have been reviewed with respect to their clouding phenomena and the effects of structural variation in the surfactant systems have been incorporated. Additives of various natures control the clouding of surfactants. Electrolytes, nonelectrolytes, organic substances as well as ionic surfactants, when present in the surfactant solutions, play a major role in the clouding phenomena. The review includes the morphological study of clouds and their applications in the extraction of trace inorganic, organic materials as well as pesticides and protein substrates from different sources.