Nano-emulsions chemical

Improved bioavailability. More than 40% of the NCEs (new chemical entity) discovered have good membrane permeability but poor aqueous solubility (i.e.. Biopharmaceutics Classification System II). By formulating the NCE in solution inside a Softgel (e.g., lipid based) or in micro/nano emulsion, the solubility and hence the bioavailability of the compound may be improved. ... 

One of the main problems with nano-emulsions is Ostwald ripening, which results from the difference in solubility between small and large droplets. The difference in chemical potential of dispersed phase droplets between different sized droplets... 

As mentioned in introduction, nano-emulsions being nonequilibrium systems require an energy input for their formation, which can be supplied mechanically (high-energy emulsification), or from the chemical energy of the components (condensation or low-energy emulsification methods). In this section, the different condensation methods, which are classified as self-emulsification and phase inversion methods, will be discussed. 

Although nano-emulsions are thermodynamically imstable systems, they may possess high kinetic stability. This property together with their transparent or translucent visual aspect and a viscosity similar to that of water makes them of special interest for practical applications. Nano-emulsions are used in the pharmaceutical field as drug delivery systems [8,17, 18,25,28-33], in cosmetics as personal-care formulations [2,4,6,7,10,19-21,23,24,27], in agrochemical applications for pesticide delivery [3,34,35], in the chemical industry for the preparation of latex particles [9,22,26,36-38], etc. In addition, the formation of kinetically stable liquid/liquid dispersions of such small sizes is of great interest from a fimdamental viewpoint. 

Nano-emulsions have found increasing use in many different applications. The advantages of nano-emulsions over conventional emulsions (or macroemulsions) are a consequence of their characteristic properties, namely small droplet size, high kinetic stability, and optical transparency. In addition, nano-emulsions offer the possibility of using microemulsion-like dispersions without the need for high surfactant concentrations. In the following, the most relevant applications of nano-emulsions in the chemical, pharmaceutical, and cosmetic fields are summarized. 

Within the last 30 years, micro emulsions have also become increasingly significant in industry. Besides their application in the enhanced oil recovery (see Section 10.2 in Chapter 10), they are used in cosmetics and pharmaceuticals (see Chapter 8), washing processes (see Section 10.3 in Chapter 10), chemical reactions (nano-particle synthesis (see Chapter 6)), polymerisations (see Chapter 7) and catalytic reactions (see Chapter 5). In practical applications, micro emulsions are usually multicomponent mixtures for which formulation rules had to be found (see Chapter 3). Salt solutions and other polar solvents or monomers can be used as hydrophilic component. The hydrophobic component, usually referred to as oil, may be an alkane, a triglyceride, a supercritical fluid, a monomer or a mixture thereof. Industrially used amphiphiles include soaps as well as medium-chained alcohols and amphiphilic polymers, respectively, which serve as co-surfactant. 

Microemulsions form spontaneously and exhibit nano-disperse structures. In contrast to emulsions there is no additional energy input necessary for the production of a microemulsion. The formation is thermodynamically favoured due to the ultra-low interfacial tension between the oil and water domains. The microemulsified fuels are in principle thermodynamically stable for an unlimited period of time only the chemical stability of the single components could be a limiting factor. A further advantage of microemulsions in contrast to emulsions is the fact that the water content can be adjusted over a broad range. Therefore, the combustion process can be customised to specific needs. An important criterion for a microemulsion to be used as fuel is that the one-phase region extends over a wide temperature range (Fig. 11.4). Mixtures of ionic and non-ionic surfactants, which exhibit almost temperature-invariant phase behaviour by optimal composition, are suitable to meet these standards. 

In this study, after a brief introduction to PI we provide the bases of a technique for the preparation of polymeric micro-porous materials, known as polyHIPE polymers (PHPs) which are now used extensively in PIM, and micro-reactor technology. These polymers are prepared through the high internal phase emulsion (HIPE) polymerization route. In order to control the pore size, the flow-induced phase inversion phenomenon is applied to the emulsification technique. The metalization of these polymers and formation of nano-structured micro-porous metals for intensified catalysis are also discussed. Finally, we illustrate the applications of these materials in chemical- and bioprocess intensifications and tissue engineering while examining the existence of several size-dependent phenomena. 

Bhanvase, B. A. and Sonawane, S. El. New approach for simultaneous enhancement of anticorrosive and mechanical properties of coatings application of water repellent nano CaC03-PANI emulsion nanocomposite in aUcyd resin. Chemical Engineering Journal, 156(1), 177-183(2010). 

Ortiz, D. P. Baydaka, E.N. Yarranton H.W.(2010). Effect of surfactants on interfacial films and stability of water-in-oil emulsions stabilized by asphaltenes. Journal off Colloid and Interface Sdence,doi 10.1016/j.jcis.2010.08.032 Pryanto, S., Mansoori, G.A., Suwono, A., (2001). Measurement of property relationships of nano-structure micelles and coacervates of asphaltene in a pure solvent. Chemical Engineering Science, 56, 6933-6939... 

---