Colloidal Dispersion Flashcards
a bounded space or an exact
quantity of a material
system
consists of at least two phases with one or more dispersed phase (internal) contained in a single continuous (external) phase
dispersion
a distinct homogenous part of a system
phase
internal phase?
dispersed phase
external or continuous phase?
dispersion medium
- diameter of particles < 1 nm
- A.k.a. True Solutions (one-phase)
molecular dispersion
- diameter of particles 1 to 500 nm
- e.g. gelatin mixture, milk
colloidal dispersion
- diameter of particles > 500 nm
- Ex. Emulsions and suspensions
coarse dispersion
particle size of colloidal dispersions?
between 1 nm to 500 nm
can colloidal dispersions be resolved by ordinary microscope?
no
what microscopes can colloidal dispersions be seen under?
electron microscope
can colloidal dispersions pass through filter paper?
yes
can colloidal dispersions pass through semipermeable membranes?
no
what is a colloidal dispersion’s diffusion rate?
slow
examples of colloidal dispersions
jelly, polymers, milk, paint, cheese
surface area per unit W or V
specific surface
- possess large specific surface
gold sol: Red -> Blue (larger) - color related to particle size
Sb and As trisulfides: Yellow -> Red (larger)
colloidal particles
colloidal form of Pt
platinum black
*More extended
→ greater Specific surface
→ greater interaction between
dispersed phase and dispersion medium
shape of colloidal particles
- Scattering of light by colloidal particles
- widely used for determining MW of colloids
Faraday-Tyndall Effect
- Used to observe the size, shape, and
structure of colloidal particles - Has higher resolution power than
optical microscope
Electron microscope
brownian movement, diffusion, osmotic pressure, sedimentation (settling), viscosity
kinetic properties of colloids
- random movement of colloidal particles
- velocity increases with decreasing particle size
Brownian Movement
- spontaneous movement from high to low
concentration until uniform system is achieved - a direct results of Brownian movement
Diffusion
diffusion can be expressed through?
Fick’s First Law
can be described by van’t Hoff equation
Osmotic Pressure
Van’t Hoff Equation:
𝝅=𝒄𝑹𝑻
- velocity of sedimentation is given by Stoke’s law
Sedimentation (Settling)
- resistance to flow of a system under applied stress
- more viscous →greater force to make it flow
- affected by shape of particles
e.g. SPHERICAL →less viscous
LINEAR →more viscous
Viscosity
pharmaceutical applications of colloids?
1.) hydrogels
2.) microparticles
3.) liposomes
4.) micelles
- a colloidal gel in which water is DM
- used for
hydrogels
uses for hydrogels
a) wound healing
b) scaffolds in tissue engineering
c) sustained-release of drugs
- developed as carriers for vaccines and
anticancer drugs - increase efficiency of drug delivery,
release and targeting
microparticles
size of microparticles
(0.2 - 5 um)
contains polymer 1 of microparticles
outer shell
contains polymer 2 of dispersed drug
core
consists of an outer membrane and an
inner liquid core
liposomes
forms liposomes
phospholipids
lipophilic compounds ->
lipophilic membrane
hydrophilic compounds ->
hydrophilic core
- similar to liposomes but do not have inner liquid compartment
- used for delivery of hydrophobic
pharmaceuticals
micelles
