Emulsions, and Blends

Broadly speaking, there are two ways of preparing emulsions One can mechanically mix the separate components, or one can induce phase separation in a homogeneous mixture 

I he diagram of Fig. 9-1 is typical of mixtures of two small molecules, or of two polymers of comparable molecular weight and comparable viscosity. Polymer solutions, or blends of two polymers with very different molecular weights, have asymmetric phase diagrams, reflecting the asymmetry of the molecular sizes (see Fig. 9-2). 

In a UCST system, when the temperature is reduced to a final value 7/ that is below the critical temperature Tc, a mixture with a concentration 0 not too far from the critical composition f)c will phase separate into two phases whose compositions lie on the opposite sides of the binodal envelope line of Fig. 9-1. The dynamics of the separation process of a single phase into these two phases is controlled by Tf, the composition j , the rate of the quench dT/dt, the viscous (or viscoelastic) properties of the phases formed, and the interfacial tension F between the two phases. Although a variety of different kinds of behavior can occur, there are two generic types of phase separation, namely, spinodal decomposition (SD) and nucleation and growth (NG). SD occurs when the mixture is quenched into a part of the phase diagram where the mixture is unstable to small variations in composition, leading to immediate growth of phase-separated domains. When the quenched 

However, for 0 1 0 0 2, the curvature of /(0) is negative, and composition D can demix by a weak fluctuation into patches with composition E and F this decreases the free energy and is thus irreversible. Weak fluctuations therefore grow spontaneously until two distinct phases appear with compositions 0i and 02.------------------------------- 

This latter case, in which / 0, is spinodal decomposition. In the former case, with / 0, phase separation occurs by nucleation and growth NG of finite fluctuations. From 

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Electro- and magnetoresponsive suspensions Foams, emulsions, and blends... 

Table 2.3 Summary of low-strain expressions for dynamic moduli of emulsions and blends.

Development of morphology in two-phase hquid/hquid systems, such as emulsions and blends, has been a subject of extensive theoretical and experimental study for over 100 years. When a buoyant, initially spherical Newtonian liquid droplet is suspended in another Newtonian liquid and subjected to shear or... 

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