DISPERSIONS - I

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

Thermodynamic Classification Lyophilic colloids Lyophobic colloids

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)

Formation of Lyophilic Colloids DispersionPhase Solution Increase in surface area (unfavorable) Increase in number of particles (favorable) Spontaneous dispersion condition:

Block Copolymer Micelle Pluronic

Microemulsions Water Pool Protein Surfactant Organic Solvent

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