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Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.
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Transcript of Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.
![Page 1: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/1.jpg)
Polymer SynthesisCHEM 421
Reading (Odian Book):
Chapter 8-1, 8-2
![Page 2: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/2.jpg)
Polymer SynthesisCHEM 421
Polymer Parameters
• Chemical structure– Chemical composition and distribution
– Sequence length and distribution
• Molecular weight and distribution
• Chain isomerism
• Morphology
• Topology
• Additives
• Cost
![Page 3: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/3.jpg)
Polymer SynthesisCHEM 421
Chain Isomerism
• Regio-isomers
• Geometric isomers
• Stereo-isomers
• Conformational isomers
![Page 4: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/4.jpg)
Polymer SynthesisCHEM 421
Geometric Isomers
CH2
CH CH
CH2
n
CH2
CH CH
CH2
n
CH2 CH
n
• 1,3-butadiene
– cis-1,4-polybutadiene
» Tg = - 90 °C
» Tm = N/A (amorphous)
– trans-1,4-polybutadiene
» Tg = - 63 °C
» Tm = 100 °C
– 1,2-atactic-polybutadiene
» Tg = 0 °C
![Page 5: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/5.jpg)
Polymer SynthesisCHEM 421
“Cis” vs. “Trans” Fats…
• Animal fats and vegetable oils– Vegetable oils polyunsaturated
(several double bonds)
– Solid fats saturated
(no double bonds)
• Hardening– Convert liquid oils to solid fats…hydrogenation
CH2
CH
O C
O
CH2 CH3
CH2
O C
O
CH2 CH CH CH2 CH3
O C
O
CH2 CH CH CH2 CH CH CH2 CH3
14
7 7
7 4
H2
PtFat
![Page 6: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/6.jpg)
Polymer SynthesisCHEM 421
Chain Isomerism
• Regio-isomers
• Geometric isomers
• Stereo-isomers
• Conformational isomers
![Page 7: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/7.jpg)
Polymer SynthesisCHEM 421
Stereoisomers
• “tacticity”
–Greek: “to put in order”
• Planar zig-zag conformation
• Relative configurations
• Isotactic
... ...
H H H H H
X X X X
H
H
H
H
H
H
H
H
H
Asymmetric carbons
![Page 8: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/8.jpg)
Polymer SynthesisCHEM 421
Stereoisomers
• Isotactic
• Syndiotactic
• Atactic
... ...
H H H H H
X X X X
H
H
H
H
H
H
H
H
H
... ...
H H H H H
X H X H
H
H
H
X
H
H
H
X
H
... ...
H H H H H
X X H X
H
H
H
H
H
X
H
H
H
![Page 9: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/9.jpg)
Polymer SynthesisCHEM 421
Model Systemsmeso- and racemic 2,4-disubstituted pentane
H3C CH3
H
X X
H
H3C CH3
X
H
X
H
CH3H3C
X XH
H
CH3H3C
X H
H X
meso
rac
![Page 10: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/10.jpg)
Polymer SynthesisCHEM 421
Model Systemsmeso- and racemic 2,4-disubstituted pentane
H3C CH3
H
X X
H
CH3H3C
X XH
H
mesoa
b
H3C CH3
X
H
X
H
CH3H3C
X H
H Xrac
a
a
![Page 11: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/11.jpg)
Polymer SynthesisCHEM 421
“Dyad” Analysis of Polymer Chains
X XH
H
... ...Meso dyad (m)
X H
H X
... ...
Rac dyad (r)
a
b
a
a
![Page 12: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/12.jpg)
Polymer SynthesisCHEM 421
“Dyad” Analysis of Polymer Chains
X XX
... ...X XX
X X
... ...X
X X X
Isotactic (mm)
Syndiotactic (rr)
X X
... ...X
X X X
Atactic or heterotactic (rm)
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Polymer SynthesisCHEM 421
Why does stereochemistry matter?
CH2 CH
n
Atactic polystyrene Tg = 105 °C Tm = N/A
Syndiotactic polystyrene Tg = 105 °C Tm = 270 °C
![Page 14: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/14.jpg)
Polymer SynthesisCHEM 421
Why does stereochemistry matter?
CH2 CH
CH3n
![Page 15: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/15.jpg)
Polymer SynthesisCHEM 421
Why does stereochemistry matter?
Isotactic Syndiotactic Atactic
Tm
(°C)165 135 N/A
Density
(g/mL)0.92 –
0.94 0.89 – 0.91 0.85
Solubility(Hydrocarbons at
Room Temp)
none medium high
Strength high medium low
CH2 CH
CH3n
![Page 16: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/16.jpg)
Polymer SynthesisCHEM 421
Stereochemistry and Synthesis
60 MHz 1H NMR spectrum ofpoly(methyl methacrylate)made using different initiators
(A) Free Radical
(B) Anionic
CH2 C
C
n
CH3
O
O
CH3
![Page 17: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/17.jpg)
Polymer SynthesisCHEM 421
“Dyad” Analysis of Polymer Chains
Meso dyad (m)
Rac dyad (r)
C CH
H
... ...
O OCH3 O OCH3
CH3 CH3b
a
aC CH3H
H
... ...
O OCH3
CH3 C
O OCH3
a
Methylene centered around 2.2 ppm
Free radical polymer: predominantly syndiotactic
Anionic polymer: predominantly isotactic
Free radical
Anionic
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Polymer SynthesisCHEM 421
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Polymer SynthesisCHEM 421
“Dyad” Analysis of Polymer Chains
Methylene Perspective
C CH
H
... ...
O OCH3 O OCH3
CH3 CH3b
a
Methyl Perspective
C CH3H
H
... ...
O OCH3
CH3 C
O OCH3
H
H
C
O OCH3
CH3
Need two monomer units to “look”or to “use” methylene protons forcharacterizing stereochemistry…
Need three monomer units to “look”or to “use” α-methyl group forcharacterizing stereochemistry…
m
rr
![Page 20: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/20.jpg)
Polymer SynthesisCHEM 421
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Polymer SynthesisCHEM 421
![Page 22: Polymer Synthesis CHEM 421 Reading (Odian Book): Chapter 8-1, 8-2.](https://reader030.fdocuments.net/reader030/viewer/2022032704/56649d575503460f94a360de/html5/thumbnails/22.jpg)
Polymer SynthesisCHEM 421
Chain Isomerism
• Regio-isomers
• Stereo-isomers
• Geometric isomers
• Conformational isomers