Spontaneous emulsification method

The grafted silicone polymers have been emulsified by the spontaneous emulsification method. The emulsification took advantage of the very low solubility of the polymers in water. Stable emulsions with sizes ranging between 200 and 500 nm have been produced. 

Fig. 5 Microscopy pictures of giiseofulvin crystals precipitated in water and out from a silicone emulsion. Top Giiseofulvin crystals precipitated by the spontaneous emulsification method 10 mg giiseofulvin in 2.5 mL acetone poured into 5 mL of 0.1 % Polysorbate 20 aqueous solution (left x 20, bar=200pm right xlOO, bar=20pm). Bottom lOmg silicone oil and 64mg giiseofulvin in 2.5 mL acetone poured into 5 mL of 0.1 % Polysorbate 20 aqueous solution (x 20, bar=200 pm)...

Such polymers are not soluble in water and were successfully emulsified by means of the spontaneous emulsification method, yielding aqueous emulsions with nanometric sizes (mean diameters from 100 to 500nm). 

Figure 11.13 The process of emulsification of a W/0 gel emulsion by the spontaneous emulsification method. An oil-in-water (0/W) microemulsion at 7°C (a) is rapidly heated to 40 °C and a gel emulsion is spontaneously formed after 38 s (b). At this stage, the emulsion does not flow if the container is turned upside down (c)...

Figure 11.14 Micrograph of a W/0 gel emulsion with a 90wt% O.l inNaCl solution, prepared by the spontaneous emulsification method...

Figure 16.3 Aspect, as seen by optical microscopy, of a water-in-oil highly concentrated emulsion with 90 wt% of dispersed phase obtained by the spontaneous emulsification method, which leads to small and low polydispersed droplets.

Using the spontaneous emulsification method (also described in Section 16.1) based on the PIT, our group has reported [20] the formation of highly concentrated... 

Figure 16.6 Micrograph of a polystyrene foam, obtained by polymerization (60 °C, 48 h) in the continuous phase of a water-in-styrene emulsion with 90% aqueous solution, prepared by the spontaneous emulsification method. The scale bar indicates 10 pm. (Adapted from Ref [20], with permission.)...

The macroporous solid foams obtained from highly concentrated emulsions prepared by the "spontaneous emulsification method, apart from being more homogeneous and with smaller cell size, also show better mechanical properties and lower densities than those prepared by conventional methods. The polystyrene foams were approximately three times stronger and approximately 50% tougher [20]. 

Highly concentrated emulsions are interesting systems for the preparation of low-density macroporous materials by polymerization in the continuous phase of the emulsions followed by the removal of the dispersed phase components. Macroporous solid foams or aerogels produced by this method consist of intercormected spongelike macropores. The droplet size distribution of the highly concentrated emulsion, which can be controlled by choosing an appropriate emulsification method (e.g. spontaneous emulsification method), is a crucial factor in determining the properties of the macroporous monoliths. 

Different methods are used in microemulsion formation a low-energy emulsification method by dilution of an oil surfactant mixture with water and dilution of a water-surfactant mixture with oil and mixing all the components together in the final composition. These methods involve the spontaneous formation of microemulsions and the order of ingredient addition may determine the formation of the microemulsion. Such applications have been performed with lutein and lutein esters. ... 

A similar technique, the so-called spontaneous emulsification solvent diffusion method, is derived from the solvent injection method to prepare liposomes [161]. Kawashima et al. [162] used a mixed-solvent system of methylene chloride and acetone to prepare PLGA nanoparticles. The addition of the water-miscible solvent acetone results in nanoparticles in the submicrometer range this is not possible with only the water-immiscible organic solvent. The addition of acetone decreases the interfacial tension between the organic and the aqueous phase and, in addition, results in the perturbation of the droplet interface because of the rapid diffusion of acetone into the aqueous phase. 

T Niwa, H Takeuchi, T Hino, N Kunou, Y Kawa-shima. Preparations of biodegradable nanospheres of water-soluble and insoluble drugs with d,l-lacti-de/glycolide copolymer by a novel spontaneous emulsification solvent diffusion method, and the drug release behavior. J Control Rel 25 89-98, 1993. 

Spontaneous emulsification and solvent diffusion method Solid lipid nanoparticles 20-80 nm Horn and Rieger, 2001 Cui et al., 2006 Ribeiro et al., 2008... 

Functional polymers have been dispersed in water by the spontaneous emulsification (or nanoprecipitation ) method [35, 36]. Such method consists in mixing a polymer solution in acetone to a large amount of water. Complete dissolution of acetone in water takes place readily and leaves the polymer as a supersaturated solution in water. The polymer forms a colloidal suspension upon precipitation. Thereafter, acetone is evaporated under reduced pressure. The resulting emulsion is made of nanometric polymer droplets in the range of 100 nm to 1 pm in the case of... 

The solvent diffusion/spontaneous emulsification process can create much smaller droplet sizes than the solvent evaporation method. In this case, the dispersed phase is composed of a water-immiscible solvent and a water-miscible solvent, which is emulsified into an aqueous solution. The diffusion of the water-miscible solvent causes turbulence and further breakup of the droplets in the emulsion. The removal of solvent can be conducted similarly to the solvent evaporation method. 

Finally, we present an interpretation of our observations in terms of diffusion paths. Basically, the diffusion equations are solved for the case of two semi-infinite phases brought into contact under conditions where there is no convection and no interfacial resistance to mass transfer. Other simplifying assumptions such as uniform density and diffusion coefficients in each phase are usually made to simplify the mathematics. The analysis shows that the set of compositions in the system is independent of time although the location of a particular composition is time-dependent. The composition set can be plotted on the equilibrium phase diagram, thus showing the existence of intermediate phases and, as explained below, providing a method for predicting the occurrence of spontaneous emulsification. 

The diffusion path method has been used to interpret nonequilibrium phenomena in metallurgical and ceramic systems (10-11) and to explain diffusion-related spontaneous emulsification in simple ternary fluid systems having no surfactants (12). It has recently been applied to surfactant systems such as those studied here including the necessary extension to incorporate initial mixtures which are stable dispersions instead of single thermodynamic phases (13). The details of these calculations will be reported elsewhere. Here we simply present a series of phase diagrams to show that the observed number and type of intermediate phases formed and the occurrence of spontaneous emulsification in these systems can be predicted by the use of diffusion paths. 

This method is particularly useful for the measurement of very low interfacial tensions (<10 mN m ) that are particularly important in applications such as spontaneous emulsification and the formation of microemulsions. Such low interfacial tensions may also be achieved with emulsions, particularly when mixed surfactant films are used. In this case, a drop of the less-dense liquid A is suspended in a tube containing the second liquid, B. On rotating the whole mass (see Figure 5.4) the drop of the liquid moves to the centre and, with an increasing speed of revolution, the drop elongates as the centrifugal force opposes the interfacial tension force that tends to maintain the spherical shape, which is that having a minimum surface area. 

The caustic method as a means of improved waterflooding for enhanced oil recovery is a complex process. Johnson has outlined four recovery mechanisms (6). Presumably, besides the ultralow tension mode, there are other requirements to ensure efficient and stable recovery of an oil in a given reservoir. To name a few spontaneous emulsification, entrainment, entrappment, wettability reversal in both directions, etc. In order to maintain a particular set of pro-... 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

Nanoparticle fabrication includes methods such as solvent evaporation, spontaneous emulsification, solvent diffusion, salting out/emulsification diffusion, and polymerization techniques [24]. The synthesis method can greatly impact the particle s physical, chemical, and biological properties and the dispersion and stability of the particles, which are important considerations in biomedical applications. The nanoparticle size and shape is of great importance because the internalization, circulation, distribution, and targeting aspects of the system can be affected by these characteristics [5]. 

T Niwa. H Takeuchi. T Hino. N Kunon, Y Kawashima. In-vitro drug release behaviour of D.L-laciide/glycolide copolymer (Plga) nanospheres with nafarelin acetate prepared by a novel spontaneous emulsification, solvent diffusion method. J. Pharm. Sci. 83 727-732. 1994. 

In path 3 (Fig. 17) the initial system is set at SAD = 0 or at SAD slightly positive, and a formulation change shifts it to SAD = 0. This can happen by changing the temperature (emulsification by the PIT method) (215) or formulation, so that the siufactant passes from one phase to the other, often producing a spontaneous emulsification. Another way to trigger an easy emulsification is by adding an alkaline aqueous solution that reacts with carboxylic acids present in the oil phase and results in interfacial formation of surface-active substances (216). 

Art and magic aside, there are three principal methods of emulsion preparation which are most often employed. A fairly comprehensive coverage of those methods is presented in the work by Becher et al., cited in the Bibliography. The three methods most often employed include (1) physical emulsification by drop rupture, (2) emulsification by phase inversion, and (3) spontaneous emulsification. The latter two methods may be described as chemically based processes in that the nature of the final emulsion will be controlled primarily by the chemical makeup of the system (the chemical nature of additives, the ratios of the two phases, temperature, etc.), while in the first it will depend more on the mechanical nature of the process (e.g., amount and form of energy input.), as well as the rheological and chemical properties of the components. Other possibilities exist (see Table 11.1) however, most are of limited practical importance. 

It is, of course, not necessary to form an emulsion by mechanical dispersion of oil and water phases. One method that has been nsed to form oil-in-water emnlsions with small and uniform drops in a nonionic snrfactant system is to start with the surfactant phase near the PIT and cool it rapidly by perhaps 20°C to 30°C (Friberg and Solans, 1968 Forster et al., 1995 Sagitani, 1992). The capacity for solubilization of oil decreases dramatically npon cooling, and the excess oil nucleates as small drops from the supersaturated microemulsion. Provided that it solubihzes substantial oil, the lamellar liqnid crystalline can also be cooled in this manner to form oil-in-water emulsions (Forster et al., 1995). Spontaneous emulsification can also be prodnced by diffusion, as discussed in Chapter 6. 

Murakami H, Kobayashi M, Takeuchi H et al (1999) Preparation of poly (d, L-lactide-co-glycolide) nanoparticles by modified spontaneous emulsification solvent diffusion method. IntJ Pharm 187 143-152... 

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