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DISPERSIONS - I

DISPERSIONS - I. Classification by Size. True Solutions (“Molecular Dispersions”) (molecules, ions) in gas, liquid (solutions ) < 1 nm, diffuse easily Fine Dispersions (Colloidal Dispersions )

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DISPERSIONS - I

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  1. DISPERSIONS - I

  2. Classification by Size • True Solutions (“Molecular Dispersions”) • (molecules, ions) in gas, liquid (solutions) • < 1 nm, diffuse easily • Fine Dispersions (Colloidal Dispersions ) • micelles, microemulsions, some suspensions (e.g. colloidal silver), “polymers”, smoke, films & foams • 1 to 500 nm, diffuse slowly, separated by ultrafiltration • Coarse Dispersions • most pharmaceutical suspensions and emulsions, dust, powder, cells, sands • >500 nm, do not diffuse, separated by filtration

  3. Thermodynamic Classification • Lyophilic colloids • Lyophobic colloids

  4. Lyophilic Colloidal Systems • Dispersions that spontaneously form from macroscopic phases, and are thermodynamically stable with respect to both enlargement of particles through their aggregation and disintegration to individual molecules Property: equilibrium size distribution (do not change in time)

  5. Formation of Lyophilic Colloids Phase Dispersion Solution • Increase in surface area (unfavorable) • Increase in number of particles (favorable) Spontaneous dispersion condition:

  6. Block Copolymer Micelle • Pluronic

  7. Microemulsions Water Pool Surfactant Protein Organic Solvent

  8. Poly(ethylene oxide) Poly(methacrylate anion) Poly(ethylene oxide) Block Ionomer Complexes Lamellas Vesicles Kabanov et al. (1998) JACS 119

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