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This lecture covers the main concepts and determination of dispersed systems, classification and preparation methods, and purification methods of biopolymer solutions. Topics include molecular dispersions, colloids, and coarse dispersions.
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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 dispersedsystems
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 may be easily separated from the continuous phase by filtration.
Classification of the dispersed systems according to the particle size Molecular-dispersion <10-9м Ultramicroheterogeneous 10-7 ÷ 10-9 м Microheterogeneous 10-4 ÷ 10-7 м Coarse-dispersion >10-4 м
Sols and emulsions are the most important types of colloidal dispersion.
Fog Fog
Classification of dispersed systems according to the particle-dispersion mediuminteraction Lyophilic (liquid-loving) good interaction of dispersed particle with dispersed medium emulsionan a water-in-oil Lyophobic (liquid-hating) (no any interaction of dispersed particle with dispersed medium)emulsionan oil-inwater
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-particleinteraction Free dispersion or no sharp line of demarcation (particles moving free) sols Not free dispersion or sharp line of demarcation (particle-particleinteraction between themself) gels, foams
Colloidal particlescan be classified according to shape as corpuscular,laminar or linear Manycolloidal systems do, in fact, contain spherical ornearly sphericalparticles. Emulsions, latexes, liquid aerosols, etc., contain sphericalparticles. Certain protein molecules are approximately spherical. Thecrystallite particles in dispersions such as gold and silver iodide solsare 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.
Dispersion These methods involve the breaking of the bigger particles to colloidal size.
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.
Dialysis • The process of separating the particles of colloids from those of crystalloids by diffusion of the mixture through semipermeable membrane (а 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).
A further modification of dialysis is the technique of electrodialysis
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:а) vacuum; b) preassure c) gel permeation chromatography а) b)
Diffusion is the tendency for molecules tomigrate from a region ofhigh concentration to a region of lowerconcentration and is a directresult 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 pressureof colloid solutions: 1. Osmotic pressure is very low:
Kineticstability • 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. а) 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 а 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. Thehigh-molecular compounds (HMC) are compounds – polymers, which have 10000 – 10000000 Da (Dalton – unit of atomic mass) molecular mass. А polymer is а 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 а three-dimensional network structure. These polymers are also called cross-linked polymers
Classificationby 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 а polymer. It is а 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 а small molecule, such as water.
