Ostwald ripening colloid stability

Buscall R, Davis SS, Potts DC. 1979. The effect of long-chain alkanes on the stability of oil-in-water emulsions the significance of Ostwald ripening. Colloid Polym Sci 257 636. 

Stability" is a ubiqitous word as applied to colloidal dispersions it may apply to more than one physical process (e.g. flocculation, settling, Ostwald ripening) and may be used in either the kinetic or thermodynamic senses. We restrict discussion here to flocculation and consider first the thermodynamic aspects. 

A.S. Kabalnov, A.V. Pertsov and E.D. Shchukin Ostwald Ripening in Two-Component Disperse Phase Systems Application to Emulsion Stability. Colloid Surfaces 24, 19 (1987). 

However, there are a number of difficulties associated with the synthesis of colloidal semiconductor particles. The preparation of stable, monodispersed, well-characterized populations of nanosized, colloidal semiconductor particles is experimentally demanding and intellectually challenging. Small and uniform particles are needed to diminish non-productive electron-hole recombinations the mean distance by which the charge carriers need to diffuse to reach the particle surface from which they are released is necessarily reduced in small particles. Monodispersity is a requirement for the observation of many of the spectroscopic and electro-optical manifestations of size quantization in semiconductor particles. Small semiconductor particles are difficult to maintain in solution in the absence of stabilizers flocculations and Ostwald ripening... 

Davis, S.S. Round, H.P. Purewal, T.S. Ostwald ripening and the stability of emulsion systems an explanation for the effect of an added third component. J. Colloid Interf. Sci. 1981, SO, 508-511. 

Kabalnov, A.S. Shchukin, E.D. Ostwald ripening theory applications to fluorocarbon emulsion stability. Adv. Colloid Interf. Sci. 1992, 38, 69-97. 

Classical theories of emulsion stability focus on the manner in which the adsorbed emulsifier film influences the processes of flocculation and coalescence by modifying the forces between dispersed emulsion droplets. They do not consider the possibility of Ostwald ripening or creaming nor the influence that the emulsifier may have on continuous phase rheology. As two droplets approach one another, they experience strong van der Waals forces of attraction, which tend to pull them even closer together. The adsorbed emulsifier stabilizes the system by the introduction of additional repulsive forces (e.g., electrostatic or steric) that counteract the attractive van der Waals forces and prevent the close approach of droplets. Electrostatic effects are particularly important with ionic emulsifiers whereas steric effects dominate with non-ionic polymers and surfactants, and in w/o emulsions. The applications of colloid theory to emulsions stabilized by ionic and non-ionic surfactants have been reviewed as have more general aspects of the polymeric stabilization of dispersions. ... 

Spadini L, Manceau A, Schindler PW, Charlet L (1994) Structure and Stability of Cd Surface Complexes on Ferric Oxides. 1. Results from EXAFS Spectroscopy. J Colloid Interface Sci 168 73-86 Steefel Cl, van Cappellen P (1990) A new kinetic approach to modehng water-rock interaction Role of nucleation, precursors, and Ostwald ripening. Geochim Cosmochim Acta 54 2657-2677 Stem LA, Durham WB, Kirby SH (1997) Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization. J Geophys Res-Solid Earth 102 5313-5325 Suzuki A, Kotera Y (1962) The kinetics of the transition of titanium dioxide. Bull Chem Soc Japan 35 1353-1357... 

Soma, 1. and Papadopoulos, K.D., Ostwald ripening in sodium dodecyl sulfate-stabilized decane-in-water emulsions, J. Colloid Interface ScL, 181, 225, 1996. 

The water solubility of the hydrophobe is a function of temperature and the nature of the continuous aqueous phase. The water solubility of the hydrophobe decreases with decreasing temperature. Furthermore, the water solubility of the monomer is also lowered as the temperature is decreased. These factors may greatly suppress the Ostwald ripening effect. As a result, the colloidal stability of the emulsion may be improved significantly by lowering the temperature. A monomeric mini-emulsion is generally prepared at room temperature prior to... 

Miniemulsion is a special class of emulsion that is stabilized against coalescence by a surfactant and Ostwald ripening by an osmotic pressure agent, or costabilizer. Compared with conventional emulsion polymerization process, the miniemulsion polymerization process allows all types of monomers to be used in the formation of nanoparticles or nanocapsules, including those not miscible with the continuous phase. Each miniemulsion droplet can indeed be treated as a nanoreactor, and the colloidal stability of the miniemulsion ensures a perfect copy from the droplets to the final product. The versatility of polymerization process makes it possible to prepare nanocapsules with various types of core materials, such as hydrophilic or hydrophobic, liquid or solid, organic or inorganic materials. Different techniques can be used to initiate the capsule wall formation, such as radical, ionic polymerization, polyaddition, polycondensation, or phase separation from preformed polymers. 

Kabalnov, A. S., Pertzov, A. V., and Shchukin, E. D., Ostwald ripening in two-component disperse phase systems application to emulsion stability. Colloid Surf., 24, 19-32 (1987). 

Stability of a macroemulsion is an important factor as this determines its extent of usability for particle preparation or various other applications. Instability is basically coalescence of the dispersed phase droplets or Ostwald ripening (growth of large droplets at the expense of much smaller ones). When this process goes on, the emulsion eventually breaks into two layers. Other processes related to stability but considered less important [3] are (a) creaming or sedimentation, the rate of which is dependent on the difference in density between the continuous and dispersed phases, droplet size, viscosity of the continuous phase and interdroplet interaction and (b) flocculation, dependent on colloidal interactions between the droplets [8, 12]. Several factors determine the stability of macroemulsions these are discussed here in brief. This discussion is largely derived from Rosen [3] and some subsequent investigations [e.g. 6, 7, 13-15]. 

Kabalnov, A. S. and E. D. Shchukin. 2002. Ostwald ripening theory Applications to fluorocarbon emulsions stability. Adv. Colloid Interface Sci. 38 69-97. 

The second method of syntl s of nanosize composites is the polymerization of a colloid solution containing colloid particles of metals [21], sulfides [7], or hydroxi [34]. A number of composites were obtained by that method, such as CdS [7], CdSe [35] and ZnS [36]. The particle size can be controlled by reaction temperature and the properties of a colloid solution thermal coagulation and Ostwald ripening can be controHed via double-layer repulsion of individual crystallites [13] by carrying out synthesis at low temperatures in non-aqueous solvents and by adsorption of foreign stabilizing molecules. For CdS and PU2... 

The Kelvin equation has numerous applications, e.g. in the stability of colloids (Ostwald ripening, see below), supersaturation of vapours, atmospheric chemistry (fog and rain droplets in the atmosphere), condensation in capillaries, foam stability, enhanced oil recovery and in explaining nucleation phenomena (homo- and heterogeneous). The Kelvin (as well as the Gibbs equations, see Equation 4.7a) are also valid for solids/solid-liquid surfaces, and they can be used for estimating the surface tensions of solids. We discuss hereafter several applications of the Kelvin equation. 

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