INVERSE MICELLAR PHASES IN TERNARY SYSTEMS OF POLAR LIPIDS/ /FAT/WATER AND PROTEIN EMULSIFICATION OF SUCH PHASES TO W/O/W-MICROEMULSION-EMULSIONS

A new approach to prepare W/O/W-double emulsions is described. The inner W/O-phase is composed of a thermodynamically stable micellar solution of inverse type, an L2-phase. A protein, caseinate, is then used to stabilize the dispersion of this phase in water. Release from the inner to the outer water phase was followed by dialysis. Phase equilibria of the two ternary systems monolaurin-water-soybean oil and tetraglycerol monolaurin-water-soybean oil are described.     

Ripening Phenomena in Emulsions — A Calorimetry Investigation

Ripening phenomena occurring within different kinds of emulsions have been studied. The emulsions concerned are simple water-in-oil (W/O) or oil-in-water (O/W) emulsions, mixed emulsions obtained by the mixture of two simple emulsions, and multiple emulsions water-in-oil-in-water (W/O/W) or oil-in-water-in-oil (O/W/O) emulsions. Composition ripening due to a mass transfer and solid ripening due to the formation of solid particles from the undercooled droplets or due to the formation of solid hydrate around the droplets have been pointed out on using a suitable calorimetric technique. For that purpose a non-diluted emulsion sample is submitted to a cooling and heating cycle during which solidification and melting temperatures and energies of the different phases are analyzed. It has been shown that correlations between these quantities and the properties of the dispersed phase permit one to get information about the ripening phenomena under study. The solution-diffusion model used for mass transfer is in good agreement with the experimental results. From the shell model used for the hydrate formation, it has been possible to deduce the formation energy and the influence of salt upon the temperature of formation.     

Preparation of a stable double emulsion (W1/O/W2): role of the interfacial films on the stability of the system

This paper presents new protocols enabling preparation of W1/O/W2 double emulsions: one, using soybean oil as the O phase, that yields edible emulsions with industrial applications, and a second that yields emulsions with a previously unattainable concentration 15% (w/w) of surfactants in the external phase (the 15% target was chosen to meet the typical industry standard). Preparation of a stable W1/O emulsion was found to be critical for the stability of the system as a whole. Of the various low HLB primary surfactants tested, only cethyl dimethicone copolyol (Abil EM90), A-B-A block copolymer (Arlacel P135), and polyglycerol ester of ricinoleic acid (Grinstead PGR-90) yielded a stable W/O emulsion. Investigation of the surface properties of those surfactants using the monolayer technique found two significant similarities: (1) stable, compressible, and reversibly expandable monolayers; and (2) high elasticity and surface potential. The high degree of elasticity of the interfacial film between W1 and O makes it highly resilient under stress; its failure to break contributes to the stability of the emulsion. The high surface potential values observed suggest that the surfactant molecules lie flat at the O/W interfaces. In particular, in the case of PGR-90, the hydroxyl (-OH) groups on the fatty acid chains serve as anchors at the O/W interfaces and are responsible for the high surface potential. The long-term stability of the double emulsion requires a balance between the Laplace and osmotic pressures (between W1 droplets in O and between W1 droplets and the external aqueous phase W2). The presence of a thickener in the outer phase is necessary in order to reach a viscosity ratio (preferably approximately 1) between the W1/O and W2 phases, allowing dispersion of the viscous primary emulsion into the W2 aqueous phase. The thickener, which also serves as a dispersant and consequently prevents phase separation due to its thixotropic properties, must be compatible with the surfactants. Finally, the interactions between the low and high HLB emulsifiers at the O/W2 interface should not destabilize the films. It was observed that such destructive interaction for the system could be prevented by the use of two high HLB surfactants in the outer aqueous phase: an amphoteric surfactant, Betaine, and an anionic surfactant, sodium lauryl ether sulfate. The combination of such pairs of surfactants was found to contribute to the films' stability.     

Ti(IV)-based catalytic membranes for efficient and selective oxidation of secondary amines

The incorporation of homogenous Ti(IV)/trialkanolamine catalyst in polymeric membranes provided new polymeric catalytic Ti(IV)-based membranes, stable and efficient as heterogeneous catalysts for chemoselective oxidations of secondary amines to nitrones by alkyl hydroperoxides. Polyvinylidene fluoride (PVDF)-based catalytic membranes gave the best results affording products in short reaction times, high yields and selectivity using as little as 1% of catalyst, comparable with the performances of the corresponding homogeneous system. PVDF-Ti membrane could be recycled up to five runs with no loss of activity.     

Interface composition of multiple emulsions: rheology as a probe

We have investigated the dynamic rheological properties of concentrated multiple emulsions to characterize their amphiphile composition at interfaces. Multiple emulsions (W1/O/W2) consist of water droplets (W1) dispersed into oil globules (O), which are redispersed in an external aqueous phase (W2). A small-molecule surfactant and an amphiphilic polymer were used to stabilize the inverse emulsion (W1 in oil globules) and the inverse emulsion (oil globules in W2), respectively. Rheological and interfacial tension measurements show that the polymeric surfactant adsorbed at the globule interface does not migrate to the droplet interfaces through the oil phase. This explains, at least partly, the stability improvement of multiple emulsions as polymeric surfactants are used instead of small-molecule surfactants.     

Properties of acrylic–polyurethane hybrid emulsions synthesized by the semibatch emulsion copolymerization of acrylates using different polyurethane particles

Aqueous acrylic–polyurethane hybrid emulsions were prepared by the semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate in the presence of eight polyurethane dispersions. The polyurethane dispersions were synthesized with isophorone diisocyanate, 1000 and 2000 molecular weight polyester polyols, 1000 molecular weight polyether polyol, butanediol, and dimethylol propionic acid. Acrylic monomers were added in the monomer emulsion feed. We studied the effect of the use of different polyurethane seed particles and the effect of different weight ratios of methyl methacrylate to butyl acrylate on the emulsion properties, microphase structure, and mechanical properties of hybrid films. The average particle size and distribution were determined by photon correlation spectroscopy. The rheological properties of polyurethane dispersions and hybrid emulsions were tested under destructive conditions by an examination of flow curves and under nondestructive conditions of oscillatory shear in a range of linear viscoelastic responses. Differential scanning calorimetry was performed to characterize the thermal‐response properties of polymeric films. The relative average molecular weights were determined by gel permeation chromatography. The interactions between the acrylic and polyurethane components in hybrid particles and particle structure were studied with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Mechanical properties such as the Koenig hardness, tensile strength, elongation at break, and Young's modulus were measured. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4050–4069, 2005     

Molecular Composition of Nonionic Vesicles Prepared from Span 80 or Span 85 by a Two‐Step Emulsification Method

The molecular compositions of the commercial nonionic surfactants Span 80 and Span 85 were analyzed by reversed phase high performance liquid chromatography (HPLC). Both surfactants are mixtures of fatty acid esters, containing monoesters, diesters, triesters, and tetraesters. While diesters dominate in the case of Span 80, Span 85 contains mainly tetraesters. Vesicles were prepared from Span 80 (or Span 85) by a two‐step emulsification method that involved homogenization and separation steps in which a portion of the surfactants was removed. The composition of the vesicles was analyzed by HPLC with respect to the different esters present. Although commercial Span 80 and Span 85 differ considerably in their molecular compositions, the ester profiles of the vesicles formed were in both cases rather similar and dominated by diesters. Therefore, the particular vesicle preparation method leads to a molecular selection of mainly those components that are prone to form bilayers.     

2′-Lipid-modified oligonucleotides via a ‘Staudinger-Vilarrasa’ reaction

We report a new access to 2′-amido-2′-deoxyuridine via a Staudinger-Vilarrasa coupling reaction for the preparation of lipid-modified oligonucleotides. One or two lipidic moieties were inserted within the oligonucleotidic sequence (LONs) leading to a repertoire of original antagomir-like molecules targeting micro RNA (miRNA or miR). Melting temperature (Tm) experiments revealed that the stability of the duplexes depends on the lipid position and the number of lipid moieties inserted within the oligonucleotide sequence. Single lipid conjugations of positions 11 and 19 of LONs targeting miR-122 do not destabilize the duplexes.     

Influence of hydrophobic monomers on secondary nucleation of hydroxyl‐functionalized latexes

The influence of butyl acrylate (BA) and methyl methacrylate (MMA) on hydroxyl functionalized latexes was investigated. The hydrophobicity of the monomer feed was varied via the BA/MMA ratio. In addition to monitoring the effect of hydrophobic monomer feed on secondary nucleation, the polymerization kinetics and final latex properties were also obtained for comparison. Five different BA to MMA molar ratios were combined with five 2‐hydroxyethyl methacrylate (HEMA) concentrations (0, 10, 20, 30 and 40 mol% in monomer composition). All latexes were synthesized through seeded semibatch emulsion polymerization process. Particle size distributions and average particle sizes of the latexes were determined by dynamic light scattering (DLS) and qualitatively compared with transmission electron microscope (TEM) images. The BA to MMA ratio significantly influences the boundary HEMA concentration at which homogeneous secondary nucleation occurs. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2190–2202     

Fat crystals: A tool to inhibit molecular transport in W/O/W double emulsions

Water-in-oil-in-water (W/O/W) double emulsions are a promising technology for encapsulation applications of water soluble compounds with respect to functional food systems. Yet molecular transport through the oil phase is a well-known problem for liquid oil-based double emulsions. The influence of network crystallization in the oil phase of W/O/W globules was evaluated by NMR and laser light scattering experiments on both a liquid oil-based double emulsion and a solid fat-based double emulsion. Water transport was assessed by low-resolution NMR diffusometry and by an osmotically induced swelling or shrinking experiment, whereas manganese ion permeation was followed by means of T₂-relaxometry. The solid fat-based W/O/W globules contained a crystal network with about 80% solid fat. This W/O/W emulsion showed a reduced molecular water exchange and a slower manganese ion influx in the considered time frame, whereas its globule size remained stable under the applied osmotic gradients. The reduced permeability of the oil phase is assumed to be caused by the increased tortuosity of the diffusive path imposed by the crystal network. This solid network also provided mechanical strength to the W/O/W globules to counteract the applied osmotic forces.