Embed Size (px)
Citation preview
Polymer SynthesisCHEM 421
• Odian Book
Chapter 5-2
Polymer SynthesisCHEM 421
Cationic Polymerization
Polymer SynthesisCHEM 421
Cationic Polymers
CH2 C
CH3
CH3
CH2 C
CH3
CH3
CH2 C CHCH3
CH2
Commercial and Technological SignificanceChemical Name Trade Name Formula
• Polyisobutylen Vistanex, Oppanol
• Isobutylene-isoprene copolymer and chlorinated copolymer
Butyl Rubberand Chlorobutyl
•Polyoxymethylene Trioxane-epoxide copolymer
~98% ~2%
~2%
DelrinCelcon
CH2 O
CH2 O C C OR
Polymer SynthesisCHEM 421
Cationic Polymers
CH2 CH2 CH2 OCH2
CH2 C CH2
CH2Cl
CH2Cl
O
Commercial and Technological SignificanceChemical Name Trade Name Formula
•Polyepichlorohydrin
•Poly(THF) or Poly(tetramethylene oxide)
•Polybischloromethyl Oxetane
Hydrin Rubber
Lycra or Spandex
Penton
CH2 CH O
CH2Cl
Polymer SynthesisCHEM 421
Cationic Polymerizations
C
R
R'
X
CH3O CH3
R = electron releasing group
R, R’= Poly(isobutylene)CH3
CH3
C2H5R
H
H
H
H
H
Polymer SynthesisCHEM 421
Cationic Polymerization
OO
CH2Cl
O
…Also cyclics
Hydrin RubberPoly(oxymethylene) Delrin
O O
O
Polymer SynthesisCHEM 421
Cationic Polymerization
HX
RX
or
H
R
Xor
HCl AlCl3
1) Priming
2) Initiation Step
H AlCl4
R H2C C R CH2 C
Polymer SynthesisCHEM 421
Cationic Polymerization
R CH2 C H2C C R CH2 C CH2 C
C H2C C
3) Propagation
4) CM
CH
C H3C C
Polymer SynthesisCHEM 421
Initiators
H2C CHA H CH2 C A
CH3 S OH
O
O
A) Bronsted Acids
ionic
covalent
A can not be too nucleophilic
HCl is not very good
Methanesulfonic acid
C ACH3
Polymer SynthesisCHEM 421
Initiators
BF3 H2O
RCl SnCl4
RCl AlCl2R
B) 1)Lewis AcidsSnCl4, AlCl3, TiCl4, BF3
R3Al, R2AlCl, RAlCl2
2) Co initiatorHOBF3 H
R SnCl5
R AlCl3R
Polymer SynthesisCHEM 421
Auto Ionization
Bone dry
AlBr32 AlBr4 AlHBr2
BF3 H2C C
Polymer SynthesisCHEM 421
Chain Transfer
More Important in Cationic than in Anionic
1) To MonomerCH2 CH HSO4 CH2 CH
CH CH CH3 CH HSO4
Polymer SynthesisCHEM 421
Chain Transfer
2) Ring Alkylation on Solvent
CH2 CH HSO4
CH2 CHH
CH3 CH HSO4
CH2 CH
Polymer SynthesisCHEM 421
Chain Transfer
CH2 CH HSO4CH2 CH
3) Ring Alkylation on Polymer
Polymer SynthesisCHEM 421
Chain Transfer
CH2 CH CH2 C
H
HSO4
4) Hydride Abstraction from Polymer
CH2 CH2 C HSO4
Polymer SynthesisCHEM 421
Poly(isobutylene)
Low MW (Mn<50,000 g/mol)Liquids adhesives caulking sealants motor oils - important
Tpzn= 0 to – 40 oC w/AlCl3
Polymer SynthesisCHEM 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
SlurryCH2 C CH2
CH3
CH3
C
CH3
CH CH2
Polymer SynthesisCHEM 421
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 SynthesisCHEM 421
Temperature Dependence
_ Xn
1/T
Polymer SynthesisCHEM 421
Temperature Dependence
As T Termination and CT
Break
change in mode of CT
[ions] vs [ion pairs]
Polymer SynthesisCHEM 421
CH2 CH2 C
CH3
CH3
A
Complications
H2C CH
CH
CH3
CH3
RH2C CH
CH
CH3
CH3
A
3-methyl-1-butene
As T , % isomerization
Polymer SynthesisCHEM 421
Complications
H2C CH
CH
CH3
CH3
3-methyl-1-butene
Temp %isomerization-130 oC 100 %-100 oC 70 %
CH2 CH
CH
CH3
CH3
CH2 CH2 C
CH3
CH3
Polymer SynthesisCHEM 421
Isomerization
H2C CH
CH
CH3
CH3
CH2
Polymer SynthesisCHEM 421
Cationic Living Polymerization
CH
OEt
H2CH3C CHI
OEt
HI/I2
-30 OCn-hexane
H3C CHI
OEt
I2 H3C CH
OEt
I3
H3C CH
OEt
