Molar Mass And Molar Mass Distribution Molecular Weight Determination Laser Light Scattering Chromatography Size Exclusion (GPC) Mass Spectroscopy Structure And Morphology Infrared Spectroscopy Nuclear Magnetic Resonance X-ray Microscopy Scanning Electron Microscopy Atomic Force Microscopy Dynamic Properties Thermal Analysis
The macromolecular architectures of synthetic polymers are determined by: Composition and its distribution Composition and its distribution Functionality and functional group distribution Functionality and functional group distribution Chain length and its distribution Chain length and its distribution Regio-chemical monomer insertion Regio-chemical monomer insertion Stereo-chemical monomer insertion Stereo-chemical monomer insertion Branching and its distribution Branching and its distribution Topological structure Topological structure 13
A protein of 100 amino acids has more than 1,500 atoms. Since there are 20 amino acids as building blocks, 20 100 possible proteins exist. Compare this with the ~ 6 x 10 77 atoms in the universe!!! Compare this with the ~ 6 x 10 77 atoms in the universe!!! Furthermore, each individual polypeptide chain has a large number of accessible conformations. 22
Number Average Molecular Weight End-group analysis determine the number of end-groups in a sample of known mass Colligative Properties most commonly osmotic pressure, but includes boiling point elevation and freezing point depression Weight Average Molecular Weight Light scattering translate the distribution of scattered light intensity created by a dissolved polymer sample into an absolute measure of weight-average M W
Viscosity Average Molecular Weight Viscometry The viscosity of an infinitely dilute polymer solution relative to the solvent relates to molecular dimension and weight. Molecular Weight Distribution Gel permeation chromatography fractionation on the basis of chain aggregate dimension in solution.
Measurement of Number Average Molecular Weight 2.3.1 End-group Analysis A. Molecular weight limitation up to 50,000 B. End-group must have detectable species a. vinyl polymer : -CH=CH2 b. ester polymer : -COOH, -OH c. amide and urethane polymer : -NH2, -NCO d. radioactive isotopes or UV, IR, NMR detectable functional group
M n = 2 x 1000 x sample wt meq COOH + meq OH C. D. Requirement for end group analysis 1. The method cannot be applied to branched polymers. 2. In a linear polymer there are twice as many end of the chain and groups as polymer molecules. 3. If having different end group, the number of detected end group is average molecular weight. 4. End group analysis could be applied for polymerization mechanism identified E. High solution viscosity and low solubility : Mn = 5,000 ～ 10,000 Measurement of Number Average Molecular Weight
Colligative properties Properties determined by the number of particles in solution rather than the type of particles. Vapour pressure lowering Freezing point depression Boiling point elevation Osmotic pressure
How Vapor Pressure Lowering Occurs Solute particles take up space in a solution. Solute particles on surface decrease number of solvent particles on the surface. Less solvent particles can evaporate which lowers the vapor pressure of a liquid. Solute particles take up space in a solution. Solute particles on surface decrease number of solvent particles on the surface. Less solvent particles can evaporate which lowers the vapor pressure of a liquid.
Vapor Pressures of Pure Water and a Water Solution The vapor pressure of water over pure water is greater than the vapor pressure of water over an aqueous solution containing a nonvolatile solute. Solute particles take up surface area and lower the vapor pressure
Vapor Pressure Lowering Let component A be the solvent and B the solute. solute B is nonvolatile Applying Raoult’s Law: where: P A = vapor pressure of the solvent in solution = vapor pressure of the solution P A * = vapor pressure of the pure solvent X A = mole fraction of the solvent
The lowering in vapor pressure, where: = mole fraction of solute
When a non volatile solute is added to solvent: Vapor pressure of solvent is lowered solution formed must be heated to higher temperature than boiling point of pure solvent to reach a vapor pressure of 1 atm. This means that non volatile solute elevates the boiling point of the solvent which we call boiling point elevation
Boiling-point elevation (Ebulliometry) T b : boiling point elevation H v : the latent heats of vaporization We use thermistor to major temperature. (1×10 -4 ℃ ) limitation of M n : below 20,000 ( C H v M n TbTb ) C=0 = RT 2 + A 2 C
Freezing-point depression (Cryoscopy) T f : freezing-point depression, C : the concentration in grams per cubic centimeter R : gas constant T : freezing point H f : the latent heats of fusion A2 : second virial coefficient ( C TfTf ) C=0 = H f M n RT 2 + A 2 C