Definition of colloid systems,
classification and
characterization.
Interparticle interactions.
Place of colloid science
Biology
Colloid chemistry
Physical chemistry
Biochemistry
Organic
Chemistry
Physics
•1. partly physical chemistry
–not the chemical composition is important
–the states are independent of the composition
•2. partly physics
–the physical properties are important
–basic law of physics are used
•3. partly biology
–the biological matters are colloids
–the mechanisms of living systems surface chemistry (enzymes)
What kind of systems are colloid
systems?
Many definitions exist:
• Those systems in which the surface plays
significant role in their behaviour.
• Colloids are those (disperse) systems which
consist particles in size of 1nm-500nm
(1nm = 10-9 m)
The colloid state is independent on the chemical
nature, every condensed phase can be turned into
colloidal system.
Are the colloid systems are homogeneous
or heterogeneous?
•
•
Homogeneous: the same physical properties (density, structure,
refractive index…) all over the phase (isotropic).
Heterogeneous: Different physical state depending on the
location.
– Gibbs phase rule: P+F = C+2
– Does the surface have an influence?
P: number of phases
F: degree of freedom
C: number of components
colloids
Are the colloid systems are homogeneous
or heterogeneous?
homogeneous
Atoms, small molecules
1010
homogeneous
0.1
smoke
macromolecules
109
108
fog
107
colloid
1
micelles
Heterogeneous
(macroscopic multiphase)
Colloid systems
10
105
104
2
10
3
10
4
pollen, bacterium
103
m
heterogeneous
microscopic
10
virus
106
10
5
10
6
nm
Classification of colloids
Colloid systems
INCOHERENT
„fluid like”
(individual particles)
The attraction (coherent forces)
is weaker than thermal energy
Colloidal
dispersions
(sols)
Solution of
macromolecules
Association
colloids
proteins
DNA, RNA
polymers
Association
of small
molecules
COHERENT
„solid” like
(network structure)
The attraction is stronger than the
thermal energy (because of cross-links)
Porodin
(porous
materials)
Reticular
(cross-linked
fibrils)
Spongoid
„sponge”-like
systems
Classification of colloids
Colloidal dispersions (sols)
Aerosols
(the medium is gas)
Xerosols
(the medium is solid)
- L/G: fog, mists, spray
- S/G: smoke, colloidal powder
- S/L/G: smog
- G/S: solid foam (bread)
- L/S: solid emulsion (opals, pearls)
- S/S: solid suspensions (pigmented
plastics)
Liosols
(the medium is liquid)
- G/L: foam (whipped cream)
- L/L: emulsion (milk)
- S/L: suspension (toothpaste, mud)
Classification of colloids
Association colloids
Macromolecular colloids
Characterization by stability
Thermodynamic
Stable
(lyophilic colloids)
Gcolloid < Ginitial
Unstable
(lyophobic colloids)
Gcolloid > Ginitial
Association and macromolecular
colloids
Colloidal dispersions
Kinetic
Stable
Unstable
NO change during the examination
Significant change can be observed
Within the examination
Characterization by colloidal state
parameters (Aladár Buzágh)
1. Dispersity in size
2. Morphology (shape, inner structure)
3. Spatial distribution
4. Interparticle interactions
Characterization by colloidal state
parameters (Aladár Buzágh)
1. Dispersity in size
Monodisperse: isometric (same size)
Heterodisperse: mixture of particles having different size
(molecular weight)
Size (molecular weight) can be determined by various methods,
and an average size will be obtained. Size distribution can be
given by the mean value and the standard deviation. In most
cases normal distribution is used.
Determination of size and it’s distribution
Depending on the method we can get different types of
average.
What type of average values can be obtained?
Number weighted average:
(Arithmetic mean)
Colligative properties always
give number weighted mean
x
 xi N i
N

 xi N i
 Ni
Mass weighted average:
(if the exact numbers
are not known)
xM

x
i
M
i
xM


M
i
i
i
Determination of size and it’s distribution
Polydispersity (PD):
Can be calculated as the ratio of the mass and number
weighted avereges.
MN
MN


i
N
i
MN


N
i
i
i
2
N
M
Mw   i i 
M
Mw
PD 
1
Mn
If the ratio is 1, than the system is monodisperse!
2
N
M
 i i
 Mi
Determination of size and it’s distribution
Example
Let’s have a system with two components (A and B)
MA=1000g/mol, MB=100000g/mol
a, 1pc A, 100pcs B
b, 50pcs A, 50pcs B
c, 100pcs A, 1pc B
1  1000 2  100  100000 2
Mw 
 99990
1  1000  100  100000
50  1000 2  50  100000 2
Mw 
 99020
50  1000  50  100000
Mw 
100  1000 2  1  100000 2
 50500
100  1000  1  100000
1  1000  100  100000
MN 
 99020
1  100
50  1000  50  100000
MN 
 50500
50  50
MN 
100  1000  1  100000
 1980
100  1
PD=1.01
PD=1.96
PD=25.51
Size determination methods
Sieve 25 m-125 mm
Wet sieve 10 m-100 m
Microscope 200 nm-150 m
Ultramicroscope 10 nm -1 m
Elektronmicroscope, (TEM, SEM surface) 1
nm- 1 m
• Sedimentation above 1 m (from suspension)
• Centrifuge 5 m and below
• Light scattering 1 nm- few m
•
•
•
•
•
Morphology
1. Prolate 2. Oblate 3. Rod 4. plate
5. coil
a. lamellar b. fibrillar
c. corpuscular
Spatial distribution, partially ordered
structures
•Homogeneous
•Diffuse (exponential)
•Heterogeneous
•Ordered
Special behaviour.
Depends on the
interparticle
interactions.
nematic
smectic
tactoid
Interactions between the particles
• The interactions between the particles can be
originated from intermolecular interactions. These
have a significant effect on the size, shape, solubility
and the stability of the colloid systems.
–
–
–
–
–
–
–
–
Ion - ion
Ion – permanent dipol
Permanent dipol – permanent dipol
Permanent dipol – induced dipol
Instantaneous dipol - Induced dipol (London dispersion)
Hidrogen bond
Stacking interaction
Repulsion
• Hydrophilic and hydrophobic interactions