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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

ReferencesReferences

References

References

References

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