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7/21/2019 6 Structure and Morphology de los materiales
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?
• Into what types of overall shapes
or conformations can polymer
chains arrange themselves?
• How do polymer chains interact
with one another.
• Into what types of forms or
morphologies do the chains organize
• What is the relationship of
conformation and morphology to
polymer microstructure.
• What is the relationship of
conformation and morphology
to macroscopic properties.
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GasGas
LiquidLiquid
SolidSolid
((Crystalline)Crystalline)
SolidSolid
((Glass)Glass)
EvaporationEvaporationCondensationCondensation
CrystallizationCrystallization
MeltingMelting
GlassGlassTransitionTransition
TemperatureTemperatureSSSSttttaaaatttteeeessss ooooff f f
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• Solids
• Liquids
• Gases
Usually consider;
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StateState
ViscoelasticViscoelastic
liquidliquid
SemicrystallineSemicrystalline
SolidSolid Glassy SolidGlassy Solid
CrystallizationCrystallization
MeltingMelting
GlassGlassTransitionTransition
TemperatureTemperature
More complex
behaviour
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“1st-Order” Transitions
GasGas
LiquidLiquid
SolidSolid
((Crystalline)Crystalline)
Small Molecules
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V o l u m e
TemperatureT c
Cool Gas
Liquid
Solid
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Crystallizable materials can form metastable glasses.
What about polymers like atactic polystyrene that cannot crystallize?
Observed Behavior depends on:•Structure
•Cooling Rate •Crystallization Kinetics
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Glass Transition
Liquid
Gas
Glass
Crystal
V o l u m e
Temperature
T g T c
Cool
Liquidor MeltGlassy
Solid
CrystallineSolid
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The Issues
• Bonding & the Forces between Chains • Conformations
• Ordered
• Disordered
• Stacking or Arrangement of Chains in
Crystalline Domains • Morphology of Polymer Crystals
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What are the forces
between chains that provide
cohesion in the solid state?
What determines
how close these
chains pack?
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Type of Type of
InteractionInteractionCharacteristicsCharacteristics ApproximateApproximate
StrengthStrengthExamplesExamples
Dispersion Forces
Dipole/dipole Interactions
(Freely Rotating)
Strong Polar Interactions and Hydrogen Bonds
Coulombic Interactions (Ionomers)
Short RangeVaries as -1/r6
Short Range
Varies as -1/r6
Complex Formbut also
Short Range
Long RangeVaries as 1/r
About0.2 - 0.5 kcal/mole
About0.5 - 2 kcal/mole
About
1 - 10 kcal/mole
About10 - 20 kcal/mole
Poly(ethylene) Polystyrene(simple hydrocarbon polymers)
Poly(acrylonitrile) PVC
NylonsPoly(urethanes)
Surlyn
Increasing Interaction StrengthIncreasing Interaction Strength
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Ordered
Disordered
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THE STUDY OF FORM AND STRUCTURE
Polymer morphology - the study of order within macromolecular solids
Our focus;
Morphology of semi - crystallinePolymers
Single crystal lamellae Spherulites Fibers
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Diffraction Rings
Diffraction Spots
Single
Crystal
Crystalline
Powder
X-ray beam
Photographic
Plate
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Diffraction angle
D i f f r a c t i o n I n
t e n s i t y
Measure Intensity
20 40 60 80
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12
12 30
30
DiffractionIntensity
Diffraction angle
Crystalline n - alkanes
Polyethylene
n - Alkanes in the Melt
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Measure IntensityMeasure Intensity
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• What is the Conformation of the Chains in the Crystalline Domains and how are they Stacked relative to one another?
• What is the Overall Shape and Form of the
Crystals?
• What are the Relative Arrangements of the Crystalline and Amorphous Parts?
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But now we can add to or list of questions, which have essentially become
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Top view of Unit CellTop view of Unit Cell
Side viewSide view
Redrawn from C. W. Bunn, Fibers from Synthetic
Polymers, R. Hill, Ed.,
Elsevier Publishing Co., Amsterdam, 1953.
The unit cell contains
segments of different chains.
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??
??
Are some chains entirely
within the crystalline part
while others are entirely
within amorphous bits ?
Do chains pass through both
regions ?
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The First ReallyThe First Really
Useful ModelUseful Model
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Courtesy of I.R. Harrison, Penn State
Reproduced with permission from P. H. Geil, Polymer Single Crystals, Robert E. Krieger Publishing Company,
Huntington, New York, 1973.
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Redrawn from K. A. Dill and P. J. Flory, Proc. Nat. Acad. Sci., 77 , 3115 (1980).
CrystallineCrystalline
OrderOrder
AmorphousAmorphous
RegionsRegions
CrystallineCrystalline
OrderOrder
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Property
Strength
Stiffness
Toughness
Optical Clarity
Barrier Properties
Solubility
Generally increases with degree of crystallinity
Generally increases with degree of crystallinity
Generally decreases with degree of crystallinity
Generally decreases with increasing degree of
crystallinity.Semi-crystalline polymers usually appear opaque
because of the difference in refractive index of the amorphous
and crystalline domains, which leads to scattering. Will depend
upon crystallite size.
Change with Increasing Degree of Crystallinity
Small molecules usually cannot penetrate or diffuse through
the crystalline domains, hence “barrier properties”, which
make a polymer useful for things like food wrap, increase withdegree of crystallinity
Similarly, solvent molecules cannot penetrate the crystalline
domains, which must be melted before the polymer will dissolve.
Solvent resistance increases with degree of crystallinity