ass. prof. Yeugenia B. Dmukhalska

1. LECTURE 5 Disperse systems. The methods of preparing of colloidal solutions. Their properties. Physical-chemical properties of biopolymer solutions. ass. prof. Yeugenia B. Dmukhalska

2. 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

3. Classification of the dispersed systems according to the particle size Ultramicroheterogeneous 10-7 ÷ 10-9 м Microheterogeneous 10-4 ÷ 10-7 м Coarse-dispersion >10-4 м

4. Sols and emulsions are by far the most important types of colloidaldispersion.

5. Classification of dispersed systems according to the particle-dispersion mediuminteraction Lyophilic (liquid-loving) good interaction of dispersed particle with dispersed medium emulsion and a water-in-oil Lyophobic (liquid-hating) (no any interaction of dispersed particle with dispersed medium)emulsion an oil-inwater

6. 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

7. 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.

8. Some model representations for non-spherical particles

9. Dispersion method of the preparation of colloid solution

10. Ball (а) andcolloid (b) mill а) b)

11. Peptization - is a process of passing of a precipitate into colloidal particles on adding suitable electrolyte. The electrolyte added is called peptizing agent.

12. 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.

13. 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 Electro-dialysis).

14. Dialysis

15. A further modification of dialysis is the technique of electrodialysis

16. Electro-dialyser

17. The most important application of dialysis is in the purification of blood in the artificial kidney

18. Ultrafiltration:а) vacuum; b) preassure c) gel permeation chromatography а) b)

19. Molecular-kinetic and optical properties of the colloidal systems

20. The motion of colloidal particle in dispersed medium Brownian motion Direction of the particle Average Brownian displacement

21. Diffusion is the tendency for molecules tomigrate from a region ofhigh concentration to a region of lowerconcentration and is a direct result of Brownian motion.

22. Osmotic pressureof colloid solutions: 1. Osmotic pressure is very low: 2. Osmotic pressure is inversely proportional to the cube of radius of particles and is directly proportional to raise to the cube (third) power of its dispersion in the same dispersed medium:

23. 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

24. 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.

25. On placing а colloidal solution under the influence of an electric field, the particles of the dispersion medium move towards oppositely charged electrode, provided the colloidal particles is called electro-osmosis.

26. The movement of colloidal particles under the influence of an electric field is called electrophoresis or cataphoresis. а) Before electrophoresis (b) After electrophoresis

27. Flocculation (coagulation) Aggregation of the particles arising from the stabilizing effect of this secondary minimum is called flocculation.

28. Hardy-Schulze Law • Greater is the valency of the oppositely charged ion of the electrolyte being added, the faster is the coagulation.

29. Sedimentation • In а gravitational field, heavy particles settle towards the foot of а column of solution by the process called sedimentation.

30. Physical-chemical properties of biopolymers.

31. 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, proteins, nucleic acids: RNA, DNA.

32. 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).

33. CLASSIFICATION HMC • Polymers are classified by different possible: • Classification by source; • Classification by structure; • Classification by synthesis; • Classification by molecular forces.

34. Classification by source • Natural (nucleic acids, polysaccharides,protein, natural rubber (polyisoprene)); • Synthetic (polyethelene, teflon, polyvinilchloride, polystyrene).

35. 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

36. Classificationby molecule form • Globular. • Fibril.

37. Classification by nature atoms, which are in molecule of polymer • Carbon contain polymers • Hetero polymers

38. Element organic • Inorganic

39. Synthesis of polymers • Addition polymerization occurs when unsaturated monomers react to form а polymer. It is а specific type of addition reaction.

40. 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. Condensation

41. 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 high-molecular compound was stat, which can solve again. • Between high-molecular compound and solvent has not boundary.

42. Properties HMC solution, which same as colloidal solutions: Size of disperse phase in solutions of high-molecular 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

43. Swelling it is process solubilityhigh-molecular compound in solvent.

44. Swilling degree (α): • α = (m – m0)/m0 = mp/m0 • or α = (V – V0)/ V0 = VP / V0 • Where: m0and V0 – massor volumepolymer before swilling; • mand V – massor volumepolymer after swilling; • mp, Vp– massor volumeof solvent, which is absorbed polymer. • Some time used mass-volume swilling degree: α= (V0 – V)/ m = cм3/g • or α = (V0 – V)100%/m