Polymer Synthesis
CHEM 421
Reading (Odian Book):
Chapter 1-4, 1-5, 1-6
Polymer Parameters
• Chemical structure
– Chemical composition and distribution
– Sequence length and distribution
• Molecular weight and distribution
• Chain isomerism
• Morphology
• Topology
• Additives
• Cost
Polymer Synthesis
CHEM 421
Chain Isomerism
• Regio-isomers
• Geometric isomers
• Stereo-isomers
• Conformational
isomers
Polymer Synthesis
CHEM 421
Conformational Isomers
H
H
P
Polymer Synthesis
CHEM 421
P
H
H
P
H
P
Conformational Isomers
Polymer Synthesis
CHEM 421
P
H
H
Energy (kcal/mol)
Cl
P
H
H
H
H
Cl
4.5
3.8
1.0
- 180
- 120
- 60
0
+60
+120
+180
Amorphous Morphology
Polymer Synthesis
CHEM 421
Glass Transition Temperature
Polymer Synthesis
CHEM 421
Copolymer Synthesis
Tetrafluoroethylene
(TFE)
Polymer Synthesis
CHEM 421
2,2-bis(trifluoromethyl)4,5-difluoro-1,3-dioxole
(PDD)
350
300
g
T in °C
250
200
150
100
50
50
60
70
80
90
100
PDD in wt-%
Udo, M.; Resnick, P.; Kipp, B. ; DeSimone*, J.M. Macromolecules 2003, 36, 7107
Mechanical Properties
Polymer Synthesis
CHEM 421
• Tensile strength
– Resistance to stretching
• Compressive strength
– The extent to which a sample can be compressed
before it fails
• Flexural strength
– Resistance to breaking or snapping when bent
• Impact strength
– Measure of toughness, ability to withstand sudden
impact
• Fatigue
– Ability to withstand repeated tensile, flexural or
compressive stress
Mechanical Properties
• Tensile stress (σ)
– σ=F/A
– dynes per square cm
• Tensile strain (ε)
– ε = ΔL / L
• Tensile Modulus (E)
–E=σ/ε
Polymer Synthesis
CHEM 421
Polymer Synthesis
CHEM 421
Processing of Amorphous
Polymers
Tprocessing = ?
Polymer Synthesis
CHEM 421
Symmetry Requirements for
Crystallinity
Atactic Polystyrene
Ph
Ph
Ph
...
...
Ph
Ph
Ph
Tm = N/A
Tg = 105 °C
Syndiotactic Polystyrene
Ph
Ph
Ph
...
...
Ph
Ph
Ph
Tm = 270 °C
Tg = 105 °C
Polymer Synthesis
CHEM 421
Processing of Semicrystalline
Polymers
Polymer Synthesis
CHEM 421
• Cool a polymer melt…
– Translational, rotational and vibrational
motions decrease…
– If certain symmetry elements are met,
crystallization can take place just below Tm
– Continue to cool, long-range backbone
segmental motion ceases at Tg
– Side groups and backbone para-phenylene
still in motion below Tg
Trashcan
Polymer Synthesis
CHEM 421
Isotactic Polypropylene
CH2
CH
CH3
Tg = - 20 °C
Tm = 170 °C
n
Processing of Semicrystalline
Polymers
Tprocessing = ?
Polymer Synthesis
CHEM 421
Processing of Semicrystalline
Polymers
Polymer Synthesis
CHEM 421
Differential Scanning Calorimetry
Polymer Synthesis
CHEM 421
Endo
DSC of a Crystalline Polymer
Polymer Synthesis
CHEM 421
DSC of a Crystalline Polymer
Polymer Synthesis
CHEM 421