Gibbs free energy flocculation

Phase separation and flocculation are similar, suggesting that the Gibbs free energy of mixing of a polymer with the solvent is responsible for both processes, and as a result, phase separation and flocculation have similar effects on heating and cooling. 

Lyophobic (liquid-hating) colloids are those in which the liquid does not show affinity for the particle. The Gibbs free energy increases when the particles are distributed through the liquid so that if attractive forces exist between the particles, there will be a strong tendency for the particles to stick together when they come into contact. This system will be unstable and flocculation will result. A lyophobic colloid can, therefore, only be dispersed if the surface is treated in some way to cause a strong repulsion to exist between the particles. Suspensions of insoluble particles in a liquid (e.g., most ceramic particles dispersed in a liquid) are well-known examples of lyophobic colloids. We therefore need to understand the attractive forces that lead to flocculation and how they can be overcome by repulsive forces to produce colloids with the desired stability. 

The reciprocal of the stabihty ratio (1/W) simply represents the fraction of collisions that effectively results in the formation of doublets. The larger the Gibbs free energy of interactions (AG), the larger the stability ratio (W). As a result, a more stable colloidal system is achieved. Under these circumstances, the particle flocculation rate can be written as... 

Reerink and Overbeek [46] showed that the maximum Gibbs free energy of interactions between an isolated pair of particles (AG ax) predominates in the slow particle flocculation process and the stability ratio (W) can be estimated by the following equation ... 

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