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
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15 MechanicalPropertyStrength,Modulus,etc Degree of
Polymerization DP Critical Limiting Value General Relationship s B
= A - (B\M n )
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16 Viscosity Degree of Polymerization General Relationship [ ]
= K M a K and a are constants Mark-Houwink-Sakurada Relation
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17 MechanicalProperty* Degree of Polymerization Viscosity
Useful Range
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Low molecular weight molecules 18 # of Molecules Molecular
Weight Single Value Synthetic Polymers Broad Range of Values
Biological Polymers # of Molecules Molecular Weight Single
Value
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The macroscopic properties of polymeric materials depend on
chain: 19 Structure Order Dynamics
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20
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21 Chemical Structure
Slide 23
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
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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
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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.
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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
Slide 27
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
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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
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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.
Slide 30
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
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Vapor Pressure Lowering Let component A be the solvent and B
the solute. solute B is nonvolatile Applying Raoults 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
Slide 32
The lowering in vapor pressure, where: = mole fraction of
solute
Slide 33
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
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(for dilute solutions) where is the molar mass of the solvent
and the molality of the solute in mol/kg
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where K b = boiling point constant or ebullioscopic constant of
the solvent for dilute solutions
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Boiling-point elevation (Ebulliometry) T b : boiling point
elevation H v : the latent heats of vaporization We use thermistor
to major temperature. (110 -4 ) limitation of M n : below 20,000 (
C H v M n TbTb ) C=0 = RT 2 + A 2 C
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(for dilute solutions) K f = molal freezing point depression
constant or cryoscopic constant
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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