Transcript Polymer Synthesis CHEM 421

Polymer Synthesis
CHEM 421
• Odian Book
Chapter 5-2
Polymer Synthesis
CHEM 421
Cationic Polymerization
Cationic Polymers
Polymer Synthesis
CHEM 421
Commercial and Technological Significance
Chemical Name
• Polyisobutylen
Trade Name
Formula
Vistanex, Oppanol
• Isobutylene-isoprene copolymer
and chlorinated copolymer
Butyl Rubber
and Chlorobutyl
~98%
~2%
Delrin
•Polyoxymethylene
Trioxane-epoxide copolymer Celcon
~2%
Cationic Polymers
Polymer Synthesis
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Commercial and Technological Significance
Chemical Name
Trade Name
•Polyepichlorohydrin Hydrin Rubber
Lycra or Spandex
•Poly(THF) or Poly(tetramethylene oxide)
•Polybischloromethyl Oxetane
Penton
Formula
Cationic Polymerizations
Polymer Synthesis
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R = electron releasing group
R, R’=
Poly(isobutylene)
Cationic Polymerization
Polymer Synthesis
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…Also cyclics
Hydrin Rubber
Poly(oxymethylene)
Delrin
Cationic Polymerization
1) Priming
2) Initiation Step
Polymer Synthesis
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Cationic Polymerization
3) Propagation
4) CM
Polymer Synthesis
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Initiators
Polymer Synthesis
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A) Bronsted Acids
ionic
A  can not be too nucleophilic
 HCl is not very good
covalent
Methanesulfonic acid
Initiators
Polymer Synthesis
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B) 1)Lewis Acids
SnCl4, AlCl3, TiCl4, BF3
R3Al, R2AlCl, RAlCl2
2) Co initiator
Auto Ionization
Bone dry
Polymer Synthesis
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Chain Transfer
Polymer Synthesis
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More Important in Cationic than in Anionic
1) To Monomer
Chain Transfer
2) Ring Alkylation on Solvent
Polymer Synthesis
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Chain Transfer
3) Ring Alkylation on Polymer
Polymer Synthesis
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Chain Transfer
Polymer Synthesis
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4) Hydride Abstraction from Polymer
Poly(isobutylene)
Low MW
(Mn<50,000 g/mol)
Liquids  adhesives
caulking
sealants
motor oils -  important
Tpzn= 0 to – 40 oC w/AlCl3
Polymer Synthesis
CHEM 421
Poly(isobutylene)
High MW
(Mn= 50,000-5,000,000)
Elastomeric
Tpzn= –100 oC w/ AlCl3
w/ 1-5 % isoprene (to vulcanize)
Methylchloride as solvent
 Slurry
Polymer Synthesis
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Butyl Rubber Advantages
• Lower Temp Capability
– -50 oC NO TM
– -70 oC = TG
• More Resistant to Ozone
• Very Low Gas Permeability
 inner tire tubes
Polymer Synthesis
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Temperature Dependence
_
Xn
1/T
Polymer Synthesis
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Temperature Dependence
Polymer Synthesis
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As T  Termination  and CT 
Break
 change in mode of CT
 [ions] vs [ion pairs]
Complications
3-methyl-1-butene
 As T  , % isomerization 
Polymer Synthesis
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Complications
Polymer Synthesis
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3-methyl-1-butene
Temp
-130 oC
-100 oC
%isomerization
100 %
70 %
Isomerization
Polymer Synthesis
CHEM 421
Cationic Living
Polymerization
Polymer Synthesis
CHEM 421