1. Lecture X Polysaccharides II
Properties of Macromolecules
Lecture #10 - Polysaccharides II - Properties of Macromolecules
Will cover general info re HCs, especially info about colloids and the colloidal state, especially their electrical properties. Also isolation and purification of HCs, and some on how to determine MWs

2. CHO Classification I Monosaccharides Oligosaccharides Polysaccharides
Comparison to Simple Sugars
Same Rxs
Effect of structural change

3. PS Properties (general)
Polysaccharides
Comparison to Simple Sugars
Same Rxs
Effect of structural change
More difficult to quantify

4. PS Properties (general)
Polysaccharides
Definitions
Hydrocolloids
Solution(s) - “A chemically and physically homogenous mixture of two or more substances.” (i.e., solvent & solute)

5. Classification of Dispersions
True solutions
Suspension
Colloidal solutions

6. Example of true solution Table Salt Dissolving in Water
Dissolving Ionic compounds
Table Salt Dissolving in Water

8. Colloids/Colloidal State
Background (history)
Crystalloids vs Colloids
Colloidal State -
A fine dispersion of one substance in another so the dispersed phase possesses different properties than before it was dispersed

9. Colloids/Colloidal State
UNITS
1 Å = meters (m) = 10-8 cm
10 Å = 1 nm = 10-9 m
1 mm = 1 m = 10-6 m = 104 Å

10. Colloids/Colloidal State
Colloidal Properties Shown by Gum Solutions I
Particle size of dispersed phase =
10 Å ‑ 1000 Å
Lack of visibility under light microscope
Ability to remain suspended

11. Colloidal Dispersions – Polymer Hydration
Hydration of polymers (“dissolves”)
H-bonding w/ -OH grps in CHOs
A solvation layer reduces strength of
ionic bonds by an order of magnitude

12. Colloids/Colloidal State
Effect of Comminution on Specific Surface
Area of a Volume of 4p/3 cm3, Divided into
Uniform Spheres of Radius R
Number of spheres R Asp cm2/cm3
Shaded region corresponds to colloidal particle-size range

13. Colloids/Colloidal State
Colloidal Properties Shown by Gum Solutions II
Particle size of dispersed phase ‑
10 Å ‑ 1000 Å
Lack of visibility under light microscope
Ability to remain suspended

14. Colloids/Colloidal State
Colloidal Properties Shown by Gum Solutions III
Dispersed phase ‑ 10 Å ‑ 1000 Å
Lack of visibility under microscope
Ability to remain suspended
Other important properties
Slow diffusion of dispersed phase
Ability to scatter light (Tyndall effect)
High interfacial energy
High adsorptive capacity

15. Colloids/Colloidal State

16. Colloids/Colloidal State
Classification - Definitions
Sol = colloidal dispersion of a solid in a liquid or gaseous medium
SUMMARY: Term "colloidal" designates a state of matter, characterized by sub‑microscopic dimensions rather than chemical composition. Any dispersed substance with the proper dimensions is in the colloidal state!

17. Colloids/Colloidal State
Colloid Properties (Electrical)
Origin of electrical charges
Ionization
Counterions
Electric double layers
Stabilization by electrostatic repulsion
Intermolecular forces
Salting out/in

18. B: Plane of shear C: Double layer sphere of influence A: Stern Layer
Colloidal
Particle
B: Plane of shear
C: Double layer
sphere of influence
A: Stern Layer

19. Electrical double layer
Schematic of double layer in a liquid at contact with a negatively-charged solid. Depending on the nature of the solid, there may be another double layer (unmarked on the drawing) inside the solid.

20. Colloidal
Particle

21. Colloids/Colloidal State
Colloid Properties (Electrical)
Origin of electrical charges
Ionization
Counterions
Electric double layers
Stabilization by electrostatic repulsion
Intermolecular forces
Salting out/in

22. d+ Dipole-dipole (H‑bonding) d- Types of bonding in gelatin gels
Ion - Ion
d+ Dipole-dipole d-
d- Dipole-dipole d+
Covalent (nonionic)
Types of bonding in gelatin gels O H d+ d-
-NH3+
Ion - Dipole O H d+ d-
-COO- H

23. Colloids/Colloidal State
Colloid Properties (Electrical)
Origin of electrical charges
Ionization
Counterions
Electric double layers
Stabilization by electrostatic repulsion
Intermolecular forces
Salting out/in

24. Equals a methyl ether group
Layer of water of hydration surrounds MC molecule
And prevents hydrophobic methyl groups from approaching each other.

25. Colloids/Colloidal State
Colloid Properties (Electrical)
Salting out/in
Hofmeister or lyotropic series (in order of increasing hydration and effectiveness in salting out HC’s.)
Monovalent cations:
Cs < Rb < NH4+ < K < Na < Li
Divalent: Ba < Sr < Ca < Mg

26. Colloids/Colloidal State
Colloid Properties (Electrical)
Salting out/in
Hofmeister or lyotropic series for anions in order of decreasing effectiveness in salting out HC’s.
F > citrate > HPO4 > tartarate > SO4 > acetate > Cl > NO3 > Br > I > SCN

27. Isolation/Purification of Hydrocolloids(HCs)
Purity of “Native” HCs
Purification Techniques
Fractional solution
Fractional precipitation
Drying

29. Molecular Weight (MWn & MWw) of Hydrocolloids(HCs)
Typical Hydrocolloid Molecular Weights
Alginates , ,000
Pectins , ,000
Guar , ,000
Gum Arabic ,000
LBG ,000
Tragacanth ,000
Carrageenan , ,000,000
Cellulosics , ,250,000
Xanthan 2,000,000

30. Molecular Weight (MW) Determination
Direct Methods (or Absolute)
Osmotic Pressure (Mn)
Ultra-Centrifugation (Mw)
Light Scattering (Mw)
Indirect Methods (or Relative)
Intrinsic Viscosity
Size Exclusion Chromatography

31. Colligative Properties
Properties that depend on the number of discrete solute units in “solution”, regardless of size (e.g., may be ions or molecules)

32. Molecular Weight (MW) Determination
Direct Methods
Osmotic Pressure
P = RT/M x C
(Van’t Hoff Eq.)
Mn = RT = X 105
(P/Co) (P/Co)
T = 25o C
C = g/100 ml
P = g/cm3
--[C]--->
Polymer Concentration
--P/[C]--->
P/[Co]--->

33. Osmometer (courtesy, Central Scientific

34. Molecular Weight (MW) Determination
Direct Methods
Osmotic Pressure
Ultra-Centrifugation
Light Scattering
Indirect Methods
Intrinsic Viscosity
Size Exclusion Chromatography

35. Molecular Weight (MW) Determination
Direct Methods
Osmotic Pressure
Ultra-Centrifugation
Light Scattering
Indirect Methods
Intrinsic Viscosity
Size Exclusion Chromatography

36. Schematic of Ostwald Viscometer