DISPERSIONS - IDISPERSIONS - I

Classification by SizeClassification by SizeTrue 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 ClassificationThermodynamic Classification

•Lyophilic colloids

•Lyophobic colloids

Lyophilic Colloidal SystemsLyophilic 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 ColloidsFormation of Lyophilic Colloids

DispersionPhase Solution

•Increase in surface area (unfavorable)

•Increase in number of particles (favorable)

Spontaneous dispersion condition: Tr k30154 2

Block Copolymer MicelleBlock Copolymer Micelle

P

Free Drug

cmc

Micelle

Unimer

m/2m/2 n

CH2CH2OHO CHCH2O

CH3CH2CH2 HO

•Pluronic

MicroemulsionsMicroemulsions

Water Pool

Protein

Surfactant

Organic Solvent

Block Ionomer ComplexesBlock Ionomer Complexes

Kabanov et al. (1998) JACS 119

VesiclesLamellas

Poly(ethylene oxide)

Poly(ethylene oxide)

Poly(methacrylate anion)