Transcript 슬라이드 1

Chapter 8. Vinyl polymerization with complex coordination catalysts
8.1 Introduction
8.2 Heterogeneous Ziegler-Natta polymerization
8.3 Homogeneous Ziegler-Natta polymerization
8.4 Ziegler-Natta copolymerization
8.5 Supported metal oxide catalysts
8.6 Alfin catalysts
8.7 Metathesis polymerization
8.1 Introduction
Karl Ziegler’s discovery ( in Germany-1950s)
at low temperatures and pressures
transition metal compound (Ti, V, Cr)
+
Organometallic compound (AlR3)
ethylene을 중합
linear polyethylene (HDPE) – denser, tougher, higher melting
because the more regular structure allows closer chain packing
and a high degree of crystallinity.
HDPE (high-density polyethylene) – bottle, pipe
LDPE (low-density polyethylene) – lap, film, coating
LLDPE (linear low-density polyethylene)
- copolymer of ethylene and 1-butene (Ziegler-type catalysts)
- less energy to produce than LDPE
8.1 Introduction
Giulio Natta’s discovery ( in Italy)
polymerizing  - olefins (1-alkenes)
+ catalysts of the type described by Ziegler
Stereoregularity polymer 생성.
(Ziegler & Natta - 1963년 Nobel Prize)
Other complex catalysts.
Reduced Metal Oxides
Alfin catalyst
TABLE 8.1 Commercially Available Polymers Synthesized with Complex coordination Catalysts
Polymer
Plastics
Polyethylene, high
density (HDPE)
Polyethylene, ultrahigh
molecular weight
(UHMWPE)
Polypropylene
Poly(1-butene)
Poly(4-methyl-1pentene)a
Polystyrene
1,4-Polybutadiene
1,4-Polyisoprene
Ethylene-1-alkeneb
copolymer (linear lowdensity polyethylene,
LLDPE)
Ethylene-propylene
block copolymers
(polyallomers)
Polydicyclopentadienec
Principal
Stereochemistry
-
Isotactic
Isotactic
Isotactic
Typical Uses
Bottles, drums, pipe, conduit, sheet,
film, wire and cable insulation
Surgical prostheses, machine
parts, heavy, heavy-duty liners
Automobile and appliance parts,
rope, cordage, webbing, carpeting
film
Film, pipe
Packaging, medical supplies, lighting
Syndiotactic
trans
trans
-
Specialty plastics
Metal cam coatings, potting
compounds for transformers
Golf ball covers, orthopedic devices
Blending with LDPE, packaging
film, Bottles
Isotactic
Food packaging, automotive trim,
toys, bottles, film, heat-sterilizable
containers
Reaction injection molding (RIM)
structural plastics
-
TABLE 8.1 Commercially Available Polymers Synthesized with Complex coordination Catalysts
Polymer
Elastomers
1,4-Polybutadiene
1,4-Polyisoprene
Poly(1-octenylene)
(polyoctenamer)c
Poly(1,3-cyclopentenylene polymer)c
Polypropylene
(amorphous)
Ethylene-propylene
copolymer (EPM, EPR)
Ethylene-propylenediene copolymer
(EPDM)
aUsully
Principal
Stereochemistry
cis
cis
trans
Typical Uses
Tires, conveyer belts, wire and cable
insulation, footware
Tires, footware, adhesives, coated
fabrics
Blending with other elastomers
trans
Molding compounds, engine mounts,
car bumper guards
-
Asphalt blends, sealants, adhesives,
cable coatings
Impact modifier for polypropylene,
car bumper guards
Wire and cable insulation, weather
stripping, tire side walls, hose, seals
-
-
copolymerized with small amounts of 1-pentene.
b1-Butene, 1-hexene, and 1-octene.
cSynthesized by ring-opening metathesis polymerization of the corresponding cycloaldene.
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
Definition
combination of
(1) transition metal compound
( an element from groups Ⅳ to Ⅷ )
- catalyst
- halides or oxyhalides of Ti, V, Cr, Mo, Zr
(2) organometallic compound
( a metal from groups Ⅰ to Ⅲ )
- cocatalyst
- hydrides, alkyls, or aryls of metals
(such as Al, Li, Zn, Sn, Cd, Be, Mg)
Most important from the commercial standpoint
TiCl3
TiCl4
+ R3Al
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
Catalyst preparation
mixing the components in a dry
inert solvent in the absence of oxygen
usually at a low temperature.
Character of Catalysts
having high reactivity toward many nonpolar monomers.
high degree of stereoregularity.
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
TiCl4-AlR3 (R = alkyl) system – initially exchange reactions
AlR3 + TiCl4
AlR2Cl + TiRCl3
(8.1)
AlR2Cl + TiCl4
AlRCl2 + TiRCl3
(8.2)
AlR3 + TiRCl3
AlR2Cl + TiR2Cl2
(8.3)
AlR3 + TiCl4
TiRCl3
AlR2Cl + TiRCl3
TiCl3 + R
AlRCl2 + TiRCl3
AlR2Cl +via
TiCl
4
TiRClcleavage
then reduction
homolytic
bond
TiR2Cl
2+R
2
AlR2Cl + TiR2Cl2
AlR3 + TiRCl3
TiRCl3
TiR2Cl2
TiCl3 + R
(8.4)
TiRCl2 + R
(8.5)
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
TiCl3 – formation by the equilibrium
TiCl4 + TiCl2
2TiCl3
Remove of radicals formed in these reactions
by
combination,
disproportionation,
or reaction with solvent.
(8.8)
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
Stereochemistry에 영향을 미치는 요인
Better activity is by using TiCl3
TiCl3의 , , ,  form
, ,  : high degree of stereoregularity
close-packed layered crystal structures.
 : 40%-50% stereoregularity, 50%-60% – linear structure (atactic polymer)
stereoregularity is very much dependent
on surface characteristics of the catalyst.
The nature of the transition metal
The alkyl groups of the cocatalyst
The presence of additives.
TABLE 8.2. Variation of Polypropylene Isotacticity with Catalysta
Catalystb
Stereoregularity (%)
AlEt3 + TiCl4
AlEt3 + -TiCl3
AlEt3 + -TiCl3
AlEt3 + ZrCl4
AlEt3 + VCl3
AlEt3 + TiCl4 + P, As,
or SB compounds
AlEt2X + TiCl3
AlEtX2 + -TiCl3 + amine
a Data
from Jordan6 and Dawans and Teyssié.7
b Et = ethyl; X = halogen.
35
45
85
55
73
35
90-99
99
8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts
Problem of Ziegler-Natta catalysts
low efficiency
difficult of catalyst remove
improvement of low efficiency (high-mileage catalysts)
Impregnating the catalyst on a solid support (MgCl2, MgO)
Ex) typical TiCl3-AlR3 catalyst yields
about 50-200g/atm,h,g(catalyst) of polyethylene
using a MaCl2-supported catalyst – 7000g/atm,h,g(catalyst)
Activity
8.2.2 Mechanism and Reactivity in Hetrerogeneous Polymerization
A. Two mechanism
a) monometallic mechanism
① Monomer is complexed at a titanium atom exposed
on the catalyst surface by a missing chlorine atom.
② Shifting the vacant octahedral position
③ Insertion reaction
④ Migration of the chain occurs to reestablish the vacant site on the surface.
SCHEME 8.1
H
X
R Cl
Ti
Cl
Cl Cl
R
CH2
CHX
R Cl
C
Cl Ti
C
Cl Cl
H H
H
R
Cl
C
Cl Ti CH2
X
Cl Cl
Cl Ti
Cl Cl
H
X
Cl
C
C
H H
R
CH X
CH2
Cl Ti
Cl Cl
Cl
SCHEME 8.1. Monometallic mechanism of Ziegler-Natta polymerization.
8.2.2 Mechanism and Reactivity in Heterogeneous Polymerization
A. Two mechanism
a) Bimetallic mechanism
① Ti 와 monomer가 -complex를 이룬다.
② Cyclic transition state가 존재한다.
③ Ionization
④ Original form
두 mechanism의 공통점
① Ti atom과 monomer가 -complex를 이룬다.
② Cyclic transition state가 존재한다.
③ Insertion에 의해 중합반응이 진행된다. (stereoregularity 결점)
Ti
R
CH2 CHX
Al
R
Ti
R
Al
R
CH
CH2
X
X
CH2
+
CH
R
Ti
R
Al
Ti
-
R
Al
R
-
CH2
CH 
+
X
R
R
CH X
CH X
-
CH2
+
Ti
Al
R
CH2
Ti
Al
R
SCHEME 8.2. Bimetallic mechanism of Ziegler-Natta polymerization.
8.2.2 Mechanism and Reactivity in Heterogeneous Polymerization
Ziegler-Natta polymerization – nonpolar monomers사용
monomer activity – decreases with increasing steric hindrance about
the double bond.
reactivity
> CH
CH2
CH2
CH2
CHCH2CH(CH3)2
CH2
CHCH3
2
> CH
2
> CH
CHCH(CH CH ) > CH
2
32
2
2
CHCH2CH3
CHCH(CH3)2
CHC(CH3)3
>
>
8.2.2 Mechanism and Reactivity in Heterogeneous Polymerization
Termination
a. transfer to monomer (8.9 and 8.10)
b. internal hydride transfer (8.11)
c. transfer to cocatalyst or to an added alkylmetal compound (8.12)
d. transfer to added hydrogen (8.13)
R
CH2
CHR
CH2
CHR
CH2CH2R + CH2 C
R
CH CH
+
CH3CH
R
R
H + CH2
CH2CH
(8.9)
(8.10)
(8.11)
C
R
AlR'3
H2
R' + R'2Al
R
H + CH3CH
CH2CH
(8.12)
(8.13)
8.2.2 Mechanism and Reactivity in Heterogeneous Polymerization
Hydrogen – the preferred transfer agent
R
R
CH2CH
+ HX
X + CH3CH
because it reacts cleanly,
leaves no residue
low in cost
Molecular weight distributions
insoluble catalyst - broad
soluble catalyst - narrower
(8.14)
8.2.2 Mechanism and Reactivity in Heterogeneous Polymerization
A
B
Polymerization
rate
C
Time
FIGURE 8.1 Types of rate curves observed in Ziegler-Natta polymerization: (A) constant; (B) decaying; and (C) decaying to constant.
8.2.3 Stereochemistry of Heterogeneous Polymerization
Isotactic polymers
insoluble catalysts
level of stereoregularity
– depending, to a degree,
on how exposed the active site is on the catalyst surface.
1-alkenes – approaches from the same side, giving rise to isotactic placement.
double bond of the monomer undergoes cis opening exclusively
cis addition to the double bond occurs
8.2.3 Stereochemistry of Heterogeneous Polymerization
Ti
H
H
C
D
Ti H
C
CH3
H C
D
Ti
C H
CH3
H
C
C
D
CH3
H D
D
C
H
C
CH3
CH3 H
erythro-Diisotactic
Ti
H
C
C
C
H
D
(8.15)
H
C
Ti H
C
CH3
D C
Ti
C H
CH3
D
C
CH3
H
H
H
D H
C
C
H
D
C
CH3 H
(8.16)
C
CH3
threo-Diisotactic
Similar behavior : 1,2-disubstituted olefins.
8.2.4 Polymerization of Dienes
1,3-butadiene : the four possible structures
cis-1,4 ; trans-1,4 ; isotatic 1,2 ; syndiotactic 1,2
TABLE 8.3. Catalysts for the Stereospecific Polymerization of Butadiene
Yield (%)
Polymer
structureb
R3Al + VCl4
97-98
trans-1,4
2
R3Al + VCl3
99
trans-1,4
2
R3Al + VOCl3
97-98
trans-1,4
2
R3Al + TiI4
93-94
cis-1,4
2
R2AlCl + CoCl2
96-97
cis-1,4
2
R3Al + Ti(OC6H9)4
90-100
1,2
13
Al/Cr = 2
~100
st-1,2
14
Al/Cr = 10
~100
it-1,2
14
Catalysta
Ref. no.
Et3Al + Cr(C6H5CN)6
a Et
= ethyl
b st = syndiotactic, it = isotactic.
8.2.4 Polymerization of Dienes
Isoprene
cis- and trans-1,4, 1,2, and 3,4 polymerization
TABLE 8.4. Catalysts for the Stereospecific Polymerization of Isoprene
Catalysta
Yield (%)
Polymer Structure
Ref. No.
R3Al + -TiClB3
91
trans-1,4
15
Et3Al + VCl3
99
trans-1,4
14
Al/Ti < 1
95
trans-1,4
14
Al/Ti > 1
96
cis-1,4
14
95
3,4
14
Et3Al + TiCl4
Et3Al + Ti(OR)4
a Et
= ethyl
8.2.4 Polymerization of Dienes
Definition of mechanism
1. whether the catalyst coordinates one(1,2 polymerization)
or both(1,4 polymerization) double bonds of the diene.
2. that coordination of a -allylic structure occurs and
that the direction of approach of monomer determines the structure.
CH2
CH
CH
CH2
CH
CH2
MXn
CH2
MXn
CH
CH
CH
CH2
CH2
CH2
(8.17)
CH CH CH2
CH22
CH2
CH
CH
MXn
CH2
CH
CH2
CH
CH2
CH
CH
CH2
CH
MXn
CH
CH2
CH2
(8.18)
8.2.4 Polymerization of Dienes
Conjugated cyclic dienes : Ziegler-Natta polymerization
Al(i-C4H9)3
TiCl3 or VCl3
(8.19)
1
Nonconjugated dienes : coordination catalysts
TiCl4-Al(C2H5)3
2
(8.20)
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.1 Metallocene Catalysts
The earliest metallocene catalysts
Cp2TiCl2
R2AlCl
4
3
MAO – used in conjunction with metallocene catalysts
(CH3)2Al
O Al
Al
Al
Al
CH3
CH3
CH3
CH3
CH3
CH3
Al
Al
Al
CH3
O
O
O
O
O
5
O
6
Al (CH3)2
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.1 Metallocene Catalysts
General structure
Examples of catalysts
R
R
X
Z
(CH3)2Si
ZrCl2
(CH3)2C
ZrCl2
M
X
R
R
8
9
7
Me2Si(Ind)2ZrCl2
M : Zr, Ti, Hf
X : Cl, alkyl
Z : C(CH3)2, Si(CH3)2, CH2CH2
R : H, alkyl
Me2C(Flu)(Cp)ZrCl2
form isotactic and syndiotactic polypropylene
usually written in condensed form
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.2 Mechanism and Reactivity with Metallocene Catalysts
Difference between metallocene and heterogeneous Ziegler-Natta catalysts
① the former have well-defined molecular structure
② polymerization occurs at one position in the molecule
③ the transition metal atom.
CH3
L
Zr
CH3
Al
+
L
O Al(CH3)O
CH3
CH3
Al(CH3)O
L
L
CH3
O
Zr
CH3
L
CH3
L
Zr
CH3
+
Zr
O
CH3
Al(CH3)O
+ Al(CH3)3
10
SCHEME 8. 3. Formation of the active site in a zirconocene catalyst.
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.2 Mechanism and Reactivity with Metallocene Catalysts
O
Al
L O
O
+
Zr CH2
L
CH2 CH2 CH2
O
L O
Al
+
O
Zr CH2
L
CH2
CH2 CH2
O
L
+
Zr CH2
L
CH2
O
Al
O
CH2
CH2
SCHEME 8.4. Possible polymerization mechanism for ethylene.
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.2 Mechanism and Reactivity with Metallocene Catalysts
Character of polymers prepared with metallocene catalysts
① Narrower molecular weight distributions
than those prepared with heterogeneous catalysts.
② Better mechanical properties.
③ Polydispersities (Mw/Mn) range from 2to 2.5 for the former,
compared with 5 to 6 for the latter.
④ The molecular weight of the metallocene-based polymers decreases
with increasing polymerization temperature, increasing catalyst concentration,
and addition of hydrogen to the monomer feed.
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.2 Mechanism and Reactivity with Metallocene Catalysts
Activities of metallocene catalysts
from 10 to 100 times higher than those of conventional Ziegler-Natta catalysts.
While it is often difficult to correlate structural variables with activity,
the following generalizations can be made :
1. For the group 4B metals, the order of activity is Zr>Ti>Hf.
2. Alkyl groups on the cyclopentadiene rings increase catalyst activity if they are
not too bulky. Large, bulky alkyl groups and electron-withdrawing groups decrease
the activity.
3. Increasing the size of the groups attached to the atom bridging the cyclopentadiene
rings (C or Si) reduces the activity.
4. MAO affords much higher catalyst activities than ethyl- or higher alkylalumoxane
cocatalysts.
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.2 Mechanism and Reactivity with Metallocene Catalysts
Another way that metallocene catalysts differ from eterogeneous catalysts
norbornene
(8.21)
11
high-melting stereoregular polymers
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization
Metallocene catalysts exhibit a remarkable ability to control polymer stereochemistry.
Structural variations
synthesis of
type CpZrCl2
(CH3)2Si
ZrCl2
8
chiral
atactic
polypropylene and higher poly(1-alkenes)
isotactic
syndiotatic
atactic polymer
(CH3)2C
ZrCl2
9
achiral
isotactic and syndiotactic polymer
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization
The much different sizes of the two pi ligands of 8
assumed to play a role in the formation of symdiotactic polymer
substitution of a methyl group on the cyclopentadiene ring of 9
hemiisotactic polypropylene
(alternate methyls isotactic, the others atactic)
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization
Producing polypropylene having alternating atactic and isotactic blocks
Ex)
The zirconium catalyst can rotate between chiral and achiral geometries
Ph
Ph
Cl
Zr
Cl
Cl
Zr
Cl
Ph
(8.22)
Ph
12
12
Thermoplastic elastomers having a range of properties
from a single monomer in a one-pot synthesis
8.3 Homogeneous Ziegler-Natta Polymerization
8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization
L
L
M
L
R
R
M
H
H
L
R
H
H
R
H
L
M
RH R H R
CH2 CHR
L
H R H R
M
L
L
HH R H
R
L
L
M
M
R
L
R
H R H R H
L
SCHEME 8.5. A mechanism for isotactic placement with a metallocene catalyst.
Optically active isotactic polymer would form from a pure enantiomer of 8
8.4 Ziegler-Natta Copolymerization
CH2 CH2
+
CH2
CH
Ziegler-Natta
catalyst
Random Copolymer
R
(R:aliphatic)
CnH2n+1
TABLE 8.5
n=2일 경우 LLDPE
n=1일 경우 EPDM(EPM)
ethylene is much more reactive than higher alkenes with
both heterogeneous and homogeneous catalysts.
EPDM is prepared with small amounts of a nonconjugated diene to facilitate crosslinking.
Typical dienes
13
ethylidenenorborene
14
dicyclopentadiene
15
1,4-hexadiene
TABLE 8.5. Representative Reactivity Ratios in Ziegler-Natta Copolymerizationa
Monomer 2
Catalystb
r1
r2
Ethylene
Propylene
TiCl3/AlR3
15.72
0.110
Ethylene
Propylene
VCl3/AlR3
5.61
0.145
Ethylene
1-Butene
VCl3/AlR3
26.90
0.043
Propylene
1-Butene
VCl3/AlR3
4.04
0.252
Ethylene
Propylene
Cp2ZrMe2
31
0.005
Ethylene
Propylene
[Z(Ind)2]ZrCl2c
6.6
0.06
Ethylene
1-Butene
Cp2ZrMe2
55
0.017
Ethylene
1-Hexene
Cp2ZrMe2
69
0.02
Monomer 1
Heterogeneous
Homogeneous
a Data
from Boor3 and Kamisky.22
b R = C H ; Cp = cyclopentadiene; Me = methyl; Z = bridging group; Ind = indene.
6 13
c Z = CH CH .
2
2
8.5 Supported Metal Oxide Catalysts
Typical supports : Alumina, silica, charcoal (숯)
metals : Cr, V, Mo, Ni, Co, W, Ti etc
Prepare of Catalysts
① The support material is impregnated with the metal ion,
then heated in air at a high temperature to form the metal oxide.
② when the support material is an oxide such as alumina,
the two oxides are coprecipitated and dried in air.
Catalyst is activated
treatment with a reducing agent
(hydrogen, metal hydride, carbon monoxide)
Poisoning of the catalyst
in the presence of water, oxygen, acetylene.
8.5 Supported Metal Oxide Catalysts
Character of the supported metal oxides
① yield polyethylene with approximately equal amounts of
saturated and unsaturated chain ends.
[M] C2H4
[M]
CH2
CH2
[M]
CH CH2 + [M] CH2CH3
(8.23)
② not as active as Ziegler-Natta catalysts,
and they do not give rise to a high degree of steroregularety.
8.6 Alfin Catalysts
alcohol + olefin
effective in polymerizing butadiene and isoprene
to very-high-molecular-weight polymer
The most effective catalyst for diene polymerization
- allylsodium, sodium isopropoxide, sodium chlofide
1.5 C5H11Cl + 3Na
1.5 C5H11Na + 1.5 NaCl
1.5 C5H11Na + (CH3)2CHOH
(8.24)
(8.25)
0.5 C5H11Na + (CH3)2CHNa + C5H12
0.5 C5H11Na + 0.5 CH2
CHCH3
0.5 CH2
CHCH2Na + 0.5 C5H12
polymerize butadiene within minutes
to a polymer having a molecular weight of several million
(8.26)
8.7 Metathesis Polymerization
Alkenes undergo a double bond redistribution reaction
R1CH
CHR2
R1CH
CHR2
R1CH
CHR2
R1CH
CHR2
C + C
C
C
C
(8.27)
C
(8.28)
[M]
16
C
[M] C
17
[M] C
8.7 Metathesis Polymerization
Synthesis of polymers by olefin metathesis
CATALYST
CATALYST
R
R R
acylic dienes
R
CATALYST
CATALYST
R
R
(8.29)
R + CH
+ CH
2 2
2 2 CHCH
(8.30)
8.7.1 Ring-Opening Metathesis Polymerization
Propagation steps
CH
+
CH
(CH2)n
CH CH
(CH2)n
[M]
[M]
(8.31)
(CH2)n
[M]
That certain group Ⅷ metal compounds
O
O
R
RuCl3, H2O
R
18
7-oxanorbornene derivatives
(8.32)
R
R
CH
Examples of three metathesis polymerizations
CH CH(CH2)6
(8.33)
19 polyoctenamer
CH CH
(8.34)
20 norbornene polymer
(8.35)
21
with cyclic polyenes
CH3
CH3
WCl6,C2H5AlCl2
(8.36)
CH2C CHCH2CH2CH CHCH2
C2H5OH
22 1—methyl-1,5-cyclooctadiene
WCl6, C2H5AlCl2
C2H5OH
[(CH2CH2) ( CH2CH
CHCH2)2]
23 cis,trans-cyclodeca-1,5-diene
W[OCH(CH2Cl)2]2 or 3
Al(C2H5)2Cl
[ (CH
24 1,3,5,7-cyclooctatetraene
CH)4 ]
(8.38)
(8.38)
8.7.2 Acyclic Diene Metathesis Polymerization
ADMET(Acyclic diene metathesis) polymerization of 1,9-decadiene
CH2
CH(CH2)6CH CH2
CATALYST
[ CH
CH(CH2)6 ]
+ CH2
CH2
(8.39)
ADMET is also useful for the synthesis of functionalized polymers.
the symthesis of an unsaturated polymer containing ester functionality.
O
CH2
O
CH(CH2)8COCH2CH2OC(CH2)8CH CH2
O
[ CH
CATALYST
(8.40)
O
CH(CH2)8COCH2CH2OC(CH2)8 ] + CH2
CH2
8.7.2 Acyclic Diene Metathesis Polymerization
addition of ethylene to an unsaturated polymer can effect depolymerization
byproduct of
ADMET
polymerization
+ CH2
CH2 (excess)
CATALYST
(8.41)
+ oligomers