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DISPERSIONS - II

DISPERSIONS - II. Thermodynamic Classification. Lyophilic colloids Lyophobic colloids. Lyophobic Colloidal Systems. Dispersions that are thermodynamically unstable and exist only during certain period of time (“ kinetic stability ”). Formation of Lyophobic Colloids. Supersaturated solution.

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DISPERSIONS - II

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  1. DISPERSIONS - II

  2. Thermodynamic Classification • Lyophilic colloids • Lyophobic colloids

  3. Lyophobic Colloidal Systems • Dispersions that arethermodynamically unstableand exist only during certain period of time (“kinetic stability”)

  4. Formation of Lyophobic Colloids Supersaturated solution Dispersion Phase Condensation Property: excessive surface energy (aggregate)

  5. Examples of Lyophobic Colloids • Emulsions (liquid in liquid) • Suspensions (solid in liquid) • Foams and films (gas in liquid) • Aerosols • Mists (liquid in gas) • Smokes ( very disperse solid in gas) • Dusts and Powders (rough solid in gas) • London smog (solid particles covered by condensed vapor in gas)

  6. Electrical Double Layer Electroneutral solution - + - - + - + + - - - - Surface charge + • Nernst potential • Zeta potential Stern layer (fixed)

  7. DLVO Theory • van der Waal’s attraction • Electrostatic repulsion Distance III II Energy • Repulsion I • Attraction Distance

  8. Effect on stability • Electrolytes in solution • Adsorption of counterions • polymers, surfactants Energy Distance

  9. Structure-Mechanical Barrier Water soluble polymer Lyophobic colloid Lyophobic colloid “Stealth” Liposomes

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