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LECTURE
Disperse systems.
The methods of preparing of
colloidal solutions. Their
properties.
Physical-chemical properties of
biopolymer solutions.
ass. prof. Iryna R. Bekus
Plan
1. The main concepts and
determination
2. Classification of the dispersed
systems
3. Preparation methods of the
dispersed systems
4. Purification methods of the
dispersed systems
Dispersed Systems
 A kinetically stable mixture of
one phase in another largely
immiscible phase. Usually at
least one length scale is in
the colloidal range.
Dispersed Systems
Dispersed phase
Continuous phase
Interface
Classification of dispersed system in agreement with
particles scale
Molecular dispersions is a true solutions of a solute phase in a solvent. The
dispersed phase (solute) is in form of separate molecules homogeneously
distributed throughout the dispersion medium(solvent). The molecule size is
less than 1 nm (4*10-8 inch). [The examples : air (a molecular mixture of
Oxygen, Nitrogen and some other gases), electrolytes (aqueous solutions of
salts)].
Colloids are micro-heterogeneous dispersed systems, in which the size of the
dispersed phase particles is within the range 1 - 1000 nm (4*10-8 - 4*10-5 inch).
The colloids phases can not be separated under gravity, centrifugal or other
forces. Dispersed phase of colloids may be separated from the dispersion
medium by micro-filtration. The examples of colloids: milk (emulsion of fat
and some other substances in water), fog (aerosol of water micro-droplets in
air), opal (colloidal silica), Silica aerogel monolith, Alumina aerogel monolith].
Coarse dispersions (suspensions) are heterogeneous dispersed systems, in
which the dispersed phase particles are larger than 1000 nm (4*10-5“). Coarse
dispersions are characterized by relatively fast sedimentation of the dispersed
phase caused by gravity or other forces. Dispersed phase of coarse dispersions
Classification of the dispersed
systems according to the particle size
Molecular-dispersion
< 10-9 Рј
Ultramicroheterogeneous
10-7 Г· 10-9 Рј
Microheterogeneous
10-4 Г· 10-7 Рј
Coarse-dispersion
>10-4 Рј
http://www.youtube.com/watch?v=q96ljVMHYLo
 Sols and emulsions are the most important
types of colloidal dispersion.
Fog
Classification of dispersed systems according to the
particle-dispersion medium
interaction
Lyophilic (liquidloving)
good interaction
of dispersed
particle with
dispersed
medium
emulsion an a
water-in-oil
Lyophobic (liquidhating)
(no any interaction
of dispersed
particle with
dispersed
medium)emulsion
an oil-in water
Types of Emulsion
A fine dispersion of one liquid in a second, largely
immiscible liquid. In foods the liquids are inevitably oil
and an aqueous solution.
mm
Water
Oil
Emulsions are an example
of colloids composed of
tiny particles suspended in
another immiscible
(unmixable) material.
Oil-in-water emulsion
Water-in-oil emulsion
Classification of dispersed systems according
to the particle-particle interaction
Free dispersion or
no sharp line of
demarcation
(particles moving
free)
sols
Not free dispersion or
sharp line of
demarcation
(particle-particle
interaction between
themself)
gels, foams
Colloidal particles can be classified
according to shape as
corpuscular, laminar or linear
Many colloidal systems do, in fact,
contain spherical or nearly
spherical particles. Emulsions,
latexes, liquid aerosols, etc.,
contain spherical particles.
Certain protein molecules are
approximately spherical. The
crystallite particles in dispersions
such as gold and silver iodide sols
are sufficiently symmetrical to
behave like spheres.
Colloidal solution
Colloidal solutions have dispersed
phase particle, which size from
10-9 to 10-7m or 1 nm to 100 nm.
http://www.youtube.com/watch?v=-jZyqqN4uqc&feature=related
Dispersion
These methods involve the
breaking of the bigger
particles to colloidal size.
Dispersion method of the
preparation of colloid solution
Mechanical
Using crusher, mill, mixer
Electrical
using the instruments for electrolytic
spraying
Acoustic
using ultrasound
Peptisation
chemical dispergation is
transfering the sediment in the
Peptization
- is a process
of passing of a precipitate into
colloidal particles on adding
suitable
electrolyte.
The
electrolyte added is called
peptizing agent.
Condensation methods of the preparation of the
colloidal solutions. It bases on the appearing of a
new phase in the homogenius phase according to
the joining of molecules, atoms, ions.
Physical
Condensation from a pair, the
substitution of a poor solvent
Chemical
FeCI3+3H2O в†’ Fe(OH)3 +3HCl
AgNO3 + KCl в†’ AgCl + KNO3
2H2S + SO2 в†’ 3S + 2H2O
Ag2O + H2 в†’ 2Ag + H 2O
Dialysis
 The process of separating the particles of
colloids from those of crystalloids by
diffusion
of
the
mixture
through
semipermeable membrane (Р° parchment
or an animal membrane) is known as
dialysis.
 The above process can be quickened if an
electric field is applied around the
membrane (the process is then called
Electrodialysis).
Dialysis
A further modification of dialysis is
the technique of electrodialysis
Electro-dialyser
The most important application of dialysis is in the
purification of blood in the artificial kidney
Hemodialysis
In hemodialysis, the patient's blood is pumped through
the blood compartment of a dialyzer, exposing it to a
partially permeable membrane.
Ultrafiltration:
Р°) vacuum; b) preassure c) gel
permeation chromatography
Р°)
b)
Diffusion
is the tendency for molecules to migrate
from a region of high concentration to a
region of lower concentration and is a
direct result of Brownian motion.
Properties
1. Physical Properties
 Heterogeneous character
 Stability
 Filterability
 Visibility
2. Colligative properties - osmotic pressure
3. Mechanical properties – Brownian movement
4. Optical properties – Tyndall affect
5. Electrical properties
Osmotic pressure
of colloid solutions:
1. Osmotic pressure is
very low:
пЃ° пЂЅ
пЃ®
V
пѓ—
RT
Na
http://www.youtube.com/watch?v=k5HMVIb4J7A&NR=1
Kinetic stability
 А major source of kinetic stability
of colloids is the existence of an
electric charge on the surfaces of
the particles. On the account of
this charge, ions of opposite
charge tend to cluster nearby, and
an ionic atmosphere is formed.
The movement of colloidal particles under the
influence of an electric field is called
electrophoresis or cataphoresis.
Р°) Before
electrophoresis
(b) After
electrophoresis
Flocculation (coagulation)
Aggregation of the
particles arising from
the stabilizing effect
of this secondary
minimum is called
flocculation.
Hardy-Schulze Law
 Greater is the valency of the
oppositely charged ion of the
electrolyte being added, the
faster is the coagulation.
Sedimentation
 In а gravitational field, heavy
particles settle towards the
foot of Р° column of solution
by the process called
sedimentation.
Biopolymers
Biopolymers are polymers produced by living organisms.
Since they are polymers, Biopolymers contain monomeric
units that are covalently bonded to form larger structures.
There are three main classes of biopolymers based on the
differing monomeric units used and the structure of the
biopolymer formed. Polynucleotides long polymers which are
composed of 13 or more nucleotide monomers, Polypeptides
short polymers of amino acids, and Polysaccharides which
are often linear bonded polymeric carbohydrate structures.
Cellulose is the most common organic compound
and biopolymer on Earth. About 33 percent of all
plant matter is cellulose. The cellulose content of
cotton is 90 percent and that of wood is 50 percent.
Physical-chemical properties of
biopolymers.
The high-molecular compounds (HMC) are
compounds – polymers, which have 10000 –
10000000 Da (Dalton – unit of atomic mass)
molecular mass.
Рђ polymer is Р° large molecule formed by the
covalent bonding of repeating smaller
molecules.
For
example
natural
macromolecules:
polysaccharides: glycogen, cellulose, starch;
nucleic acids: RNA, DNA; proteins.
Biological role of polymers




Biopolymers, have a lot functions:
Catalytic effect– enzymes;
As regulators – hormones;
is the storage and transfer of genetic
information.(DNA);
 Storage energy (Starch, glycogen);
 Protection - immunoglobulin;
 Structural (collagen, keratins, fibril).
CLASSIFICATION HMC




Polymers are classified by different possible:
Classification by source;
Classification by structure;
Classification by synthesis;
Classification by molecular forces.
Classification by source
 Natural (nucleic acids, polysaccharides,
protein, natural rubber (polyisoprene));
 Synthetic
(polyethelene,
teflon,
polyvinilchloride, polystyrene).
Classification by structure
Linear polymers. In these polymers, the
monomers are joined together to form
long straight chains of polymer
molecules. Because of the close
packing of polymer chains, linear
polymers have high melting point,
high densities and high tensile
(pulling) strength.
Branched chain polymers. In these
polymers, the monomer units not only
combine to produce the linear chain
(called the main chain) but also form
branches along the main chain
Three-dimensional network polymers. In
these polymers, the initially formed
linear polymer chains are joined
together to form Р° three-dimensional
network structure. These polymers
are also called cross-linked polymers
Classification by molecule form
 Globular.
 Fibril.
Classification by nature atoms, which
are in molecule of polymer
 Carbon contain
polymers
 Hetero polymers
 Element organic
 Inorganic
Synthesis of polymers
 Addition
polymerization
occurs when
unsaturated
monomers react to
form Р° polymer. It
is Р° specific type of
addition reaction.
Condensation
Condensation polymers are formed by the
head-to-tail joining of monomer units. This
is usually accompanied by the loss of Р°
small molecule, such as water.
Properties
Properties HMC solution, which same as
true solutions:
 Solutions of high-molecular compounds
are stable as molecular solutions;
 Solutions of high-molecular compounds
are convertible. If high-molecular
compound was solved that the molecular
solution will be farmed. And if this
solution to strip to dryness, so highmolecular compound was stat, which can
solve again.
 Between high-molecular compound and
solvent has not boundary.
Properties HMC solution, which same
as colloidal solutions:
Size of disperse phase in solutions of highmolecular compounds are same as in
colloidal solutions (10-7 - 10-9 m);
High-molecular compounds can not
permeate through semipermeable
membrane;
High-molecular compounds slowly are
diffused in solutions.
Specific properties HMC solution:
For solutions of high-molecular compounds
are characteristic the swelling and high
viscosity
Definition of Micelles
(Associated colloids).
 There are some substances which at low
concentrations behave as normal strong
electrolytes but at higher concentrations
exhibit colloidal behavior due to the
formation of aggregated particles. These
associated particles are called micelles or
associated colloids.
Preparation of Lyophilic Sols
 Since lyophilic sols are quite stable, they
can be easily prepared by shaking the
lyophilic substance with the dispersion
medium.
 Examples are: Colloidal sols of gum, starch,
gelatine and egg albumin.
Preparation of Lyophobic Sols
• Lyophobic sols are prepared by two methods. They are:
• 1) Condensation methods - In condensation methods
particles of atomic or molecular size are induced to
combine to form aggregates of colloidal dimensions. To
achieve this, chemical as well as physical methods are
employed.
• 2) Dispersion methods. - In dispersion methods,
colloidal particles are obtained by breaking large
particles of a substance in the presence of a dispersion
medium. Since the sols formed are unstable, they are
stabilized by adding stabilizing agents.
Micelles
A micelle is formed when a
variety of molecules
including soaps and
detergents are added to
water. The molecule may be
a fatty acid, a salt of a fatty
acid (soap), phospholipids,
or other similar molecules.
The molecule must have a
strongly polar "head" and a
non-polar hydrocarbon
chain "tail".
Structure of a micelle
 Swelling it is process solubility high-molecular
compound in solvent.
 Swilling degree (α):
 α = (m – m0)/m0 = mp/m0
 α = (V – V0)/ V0 = VP / V0
 Where: m0 and V0 – mass or volume polymer
before swilling;
 m and V – mass or volume polymer after swilling;
 mp, Vp – mass or volume of solvent, which is
absorbed polymer.
 Some time used mass-volume swilling degree:
 α= (V0 – V)/ m = cм3/g
 α = (V0 – V)100%/m
Thank you for attention
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