DISPERSIONS - I. Classification by Size True Solutions (“Molecular Dispersions”) (molecules,...
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Transcript of DISPERSIONS - I. Classification by Size True Solutions (“Molecular Dispersions”) (molecules,...
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
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