Polymer Characterization
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Transcript of Polymer Characterization
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Polymer CharacterizationTopicsTopicsMolar Mass And Molar Mass DistributionMolecular Weight DeterminationLaser Light ScatteringChromatography Size Exclusion (GPC)Mass SpectroscopyStructure And MorphologyInfrared SpectroscopyNuclear Magnetic ResonanceX-ray MicroscopyScanning Electron MicroscopyAtomic Force MicroscopyDynamic PropertiesThermal Analysis
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Find them Collectively on one CDDevelopment of PolymersDevelopment of Polymers11ProductConceptDesignPropertiesFundamentalsSynthesisRole of Polymer Characterization12SynthesisStructurePropertiesCharacterizationStructure and Properties of PolymersThe macromolecular architectures of synthetic polymers are determined by:
Composition and its distribution
Functionality and functional group distribution
Chain length and its distribution
Regio-chemical monomer insertion
Stereo-chemical monomer insertion
Branching and its distribution
Topological structure 13Molecular WeightMolecular Weight Effect on Properties15MechanicalProperty
Strength,Modulus,etcDegree of PolymerizationDP CriticalLimiting ValueGeneral Relationship
sB = A - (B\Mn)Molecular Weight Effect on Flow16ViscosityDegree of PolymerizationGeneral Relationship[h] = K Ma K and a are constants Mark-Houwink-Sakurada RelationOptimization of Molecular Weight17MechanicalProperty*
Degree of PolymerizationViscosityUseful RangeMolecular Weight DistributionLow molecular weight molecules18# of MoleculesMolecular WeightSingle ValueSynthetic PolymersBroad Range of ValuesBiological Polymers# of Molecules# of MoleculesMolecular WeightMolecular WeightSingle ValueStructure-property Relationships for PolymersThe macroscopic properties of polymeric materials depend on chain:19StructureOrderDynamicsDiagram of Oligomers of PE20
Molecular Diagrams of Polymers21
Chemical StructureBiomaterials and Their ComplexityA protein of 100 amino acids has more than 1,500 atoms.
Since there are 20 amino acids as building blocks, 20100 possible proteins exist.Compare this with the ~ 6 x 1077 atoms in the universe!!!
Furthermore, each individual polypeptide chain has a large number of accessible conformations.22Methods of Molecular Weight DeterminationNumber Average Molecular WeightEnd-group analysisdetermine the number of end-groups in a sample of known massColligative Propertiesmost commonly osmotic pressure, but includes boiling point elevation and freezing point depression
Weight Average Molecular WeightLight scatteringtranslate the distribution of scattered light intensity created by a dissolved polymer sample into an absolute measure of weight-average MW
23Methods of Molecular Weight DeterminationViscosity Average Molecular WeightViscometryThe viscosity of an infinitely dilute polymer solution relative to the solvent relates to molecular dimension and weight.
Molecular Weight DistributionGel permeation chromatographyfractionation on the basis of chain aggregate dimension in solution.24Measurement 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 Mn =2 x 1000 x sample wtmeq COOH + meq OHC. 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 andgroups 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 mechanismidentified
E. High solution viscosity and low solubility : Mn = 5,000 10,000 Measurement of Number Average Molecular WeightColligative propertiesProperties determined by the number of particles in solution rather than the type of particles.
Vapour pressure loweringFreezing point depressionBoiling point elevationOsmotic pressure
How Vapor Pressure Lowering OccursSolute 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 SolutionThe 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 pressureVapor Pressure Lowering
Let component A be the solvent and B the solute.solute B is nonvolatile Applying Raoults Law:where: PA= vapor pressure of the solvent in solution= vapor pressure of the solutionPA*= vapor pressure of the pure solventXA= mole fraction of the solventThe lowering in vapor pressure,
where:
= mole fraction of soluteBoiling Point ElevationWhen 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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Boiling Point Elevation
(for dilute solutions)where
is the molar mass of the solvent and the molality of the solute in mol/kg Boiling Point Elevation
where Kb= boiling point constant or ebullioscopic constant of the solvent
for dilute solutions
Boiling-point elevation (Ebulliometry)
Tb: boiling point elevation Hv: the latent heats of vaporization
We use thermistor to major temperature. (110-4) limitation of Mn : below 20,000
(CHvMnTb )C=0 =RT2+ A2CFreezing Point Depression
Addition of a nonvolatile solute to a solution lowers the freezing point of the solution relative to the pure solvent.Freezing Point Depression
(for dilute solutions)Kf= molal freezing point depression constant or cryoscopic constant
Freezing-point depression (Cryoscopy)
Tf : freezing-point depression, C : the concentration in grams per cubic centimeter R : gas constant T : freezing point Hf: the latent heats of fusion A2 : second virial coefficient
(CTf )C=0 =Hf MnRT2+ A2C