Cationic CNC-stabilized Pickering emulsions of linseed oil for hydrophobic coatings† † Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3ra01412f
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ABSTRACT:
SUBMITTER: Jaekel E
PROVIDER: S-EPMC10240255 | biostudies-literature | 2023 Jun
REPOSITORIES: biostudies-literature
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Project description:The possibility of stabilizing emulsions of water and non-polar alkane with pure, coloured organic pigment particles is explored. Seven pigment types each possessing a primary colour of the rainbow were selected. Their solubility in water or heptane was determined using a spectrophotometric method and their surface energies were derived from the contact angles of probe liquids on compressed disks of the particles. As expected, most of the pigments are relatively hydrophobic but pigment orange is quite hydrophilic. At equal volumes of oil and water, preferred emulsions were water-in-oil (w/o) for six pigment types and oil-in-water (o/w) for pigment orange. The emulsion type is in line with calculated contact angles of the particles at the oil-water interface being either side of 90°. Their stability to coalescence increases with particle concentration. Emulsions are shown to undergo limited coalescence from which the coverage of drop interfaces by particles has been determined. In a few cases, close-packed primary particles are visible around emulsion droplets. At constant particle concentration, the influence of the volume fraction of water (φw) on emulsions was also studied. For the most hydrophilic pigment orange, emulsions are o/w at all φw, whereas they are w/o for the most hydrophobic pigments (red, yellow, green and blue). For pigments of intermediate hydrophobicity however (indigo and violet), catastrophic phase inversion becomes possible with emulsions inverting from w/o to o/w upon increasing φw. For the first time, we link the pigment surface energy to the propensity of emulsions to phase invert transitionally or catastrophically.
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Project description:Colloidal particle-stabilized emulsions have recently gained increasing interest as delivery systems for essential oils. Despite the use of silica particles in food and pharmaceutical applications, the formation and release of hydrophilic and hydrophobic silica particle-stabilized emulsions are still not well studied. Thus, in this study, the structures of hydrophilic (A200, A380, 244FP, and 3150) and hydrophobic (R202 and R106) silica were deeply characterized using the solid state, contact angle, and other properties that could affect the formation of emulsions. Following that, Mosla chinensis essential oil emulsions were stabilized with different types of silica, and their characteristics, particularly their release behavior, were studied. Fick's second law was used to investigate the mechanism of release. Additionally, six mathematical models were employed to assess the experimental data of release: zero-order, first-order, Higuchi, Hixson-Crowell, Peppas, and Page models. The release mechanism of essential oils demonstrated that diffusion was the dominant mechanism, and the fitting results for the release kinetics confirmed that the release profiles were governed by the Higuchi model. The contact angle and specific surface area were the key properties that affect the release of essential oils from emulsions. Hydrophilic A200 was found to be capable of delivering essential oils more efficiently, and silica particles could be extended to achieve the controlled release of bioactives. This study showed that understanding the impact of silica particles on the release behavior provided the basis for modulating and mapping material properties to optimize the performance of emulsion products.
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Project description:Chitin nanofibrils (NCh, ∼10 nm lateral size) were produced under conditions that were less severe compared to those for other biomass-derived nanomaterials and used to formulate high internal phase Pickering emulsions (HIPPEs). Pre-emulsification followed by continuous oil feeding facilitated a "scaffold" with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with internal phase volume fraction as high as 88%. The high stabilization ability of rodlike NCh originated from the restricted coarsening, droplet breakage and coalescence upon emulsion formation. This was the result of (a) irreversible adsorption at the interface (wettability measurements by the captive bubble method) and (b) structuring in highly interconnected fibrillar networks in the continuous phase (rheology, cryo-SEM, and fluorescent microscopies). Because the surface energy of NCh can be tailored by pH (protonation of surface amino groups), emulsion formation was found to be pH-dependent. Emulsions produced at pH from 3 to 5 were most stable (at least for 3 weeks). Although at a higher pH NCh was dispersible and the three-phase contact angle indicated better interfacial wettability to the oil phase, the lower interdroplet repulsion caused coarsening at high oil loading. We further show the existence of a trade-off between NCh axial aspect and minimum NCh concentration to stabilize 88% oil-in-water HIPPEs: only 0.038 wt % (based on emulsion mass) NCh of high axial aspect was required compared to 0.064 wt % for the shorter one. The as-produced HIPPEs were easily textured by taking advantage of their elastic behavior and resilience to compositional changes. Hence, chitin-based HIPPEs were demonstrated as emulgel inks suitable for 3D printing (millimeter definition) via direct ink writing, e.g., for edible functional foods and ultralight solid foams displaying highly interconnected pores and for potential cell culturing applications.
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Project description:Celluloses are renewable and biodegradable natural resources. The application of celluloses as oil-in-water Pickering emulsifiers is still quite limited. In this paper, cellulose nanofibrils (CNFs) with oxidation degrees (DOs) of 52.8% and 92.7% (DO50 and DO90) were obtained from TEMPO-mediate oxidation for microcrystalline cellulose (MC). The production of carboxyl groups of CNFs were confirmed by FT-IR and 13C solid-NMR. CNF-stabilized O/W Pickering emulsion showed excellent colloidal stability compared with un-oxidized cellulose by Turbiscan stability analysis. Additionally, CNF-stabilized Pickering emulsions showed stable colloidal properties in simulated intestinal fluid (SIF). Most importantly, in vitro fatty acid release kinetics under SIF showed that CNFs have strong inhibitory lipid digestion behavior. Our results suggest that the oxidation modification not only improves their emulsification activity but also promotes their application in oil digestion inhibition, providing inspiration for designing and developing low-calorie food products.
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Project description:Colloidal polystyrene (PS) latex particles in water can undergo interesting charge reversal in the presence of particular electrolytes. It is worth exploring the effect of charge reversal on the properties of Pickering emulsions they stabilize. Herein, emulsions stabilized by PS latex particles possessing different surface groups (sulfate, amidine, or carboxyl) were prepared in the presence of tetrapentylammonium bromide (TPeAB) or sodium thiocyanate (NaSCN) electrolytes. The effect of salt concentration on the charge of the particles and their colloid stability was measured. Emulsions were prepared from aqueous dispersions, and their type and stability were determined. The three-phase contact angle of particles at the planar oil-water interface was also measured using a gel trapping technique. It was found that the type of emulsion stabilized by latex particles is dominated by the hydrophobic PS portion on particle surfaces, although their surface charge is strongly affected by electrolyte addition. Preferred emulsions were always water-in-oil with dodecane, and charge reversal had little influence on the emulsion type and stability. However, transitional phase inversion of emulsions stabilized by carboxyl latex particles occurred on adding salt when the oil was a low-viscosity polydimethylsiloxane.
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Project description:β-Cyclodextrin (β-CD) can combine with oil and other guest molecules to form amphiphilic inclusion complexes (ICs), which can be adsorbed on the oil-water interface to reduce the interfacial tension and stabilize Pickering emulsions. However, the subtle change of β-CD in the process of emulsion preparation is easily ignored. In this study, β-CD and ginger oil (GO) were used to prepare the Pickering emulsion by high-speed shearing homogenization without an exogenous emulsifier. The stability of the emulsion was characterized by microscopic observation, staining analysis, and creaming index (CI). Results showed that the flocculation of the obtained Pickering emulsion was serious, and the surface of the droplets was rough with lamellar particles. In order to elucidate the formation process of the layered particles, the GO/β-CD ICs were further prepared by ball milling method, and the X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and interfacial tension analyses found that β-CD and GO first formed amphiphilic nanoscale small particles (ICs) through the host-guest interaction, and the formed small particles were further self-assembled into lamellar micron-scale amphiphilic ICs microcrystals. These amphiphilic ICs and microcrystals aggregated at the oil-water interface and finally formed the Pickering emulsion. In this study, by exploring the formation process and evolution of GO/β-CD self-assembly, the formation process and stabilization mechanism of the β-CD-stabilized GO Pickering emulsion were clarified preliminarily, with the aim of providing a theoretical basis for the development of high-performance CD-stabilized Pickering emulsions.
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