Hanyang Univ.Hanyang Univ.
Spring 2006Chap 11. Non-Radical Addition Polymerization
B-Z + CH2=CHX B-CH2-CH- Z+
X
Initiation:
Propagation:
M- Z+ + M MM- Z+
Termination:
M- Z+ + HT MH + ZT
General Scheme
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
CH LiCH3CH2
CH3
CH2 CH CHCH3CH2
CH3
CH2 CH Li
CH2 CH Li CH2 CH CH2 CH CH2CH Li
CH2 CH Li H OH CH2 CH2 Li OH
Initiation:
Propagation:
Termination:
+
+
+ +
Styrene Polymerization
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
• Negative centers repel one another and thus termination by recombination is not possible. An ideal polymerization is “living”, which does not terminate until a terminator is added.
• Initiation is normally very fast relative to propagation and all chains grow simultaneously. This leads to polymers with low polydispersity or monodispersity.
• Theoretically:
nn
w
xM
M 11
• The rate of polymerization for methacrylates and styrenes is high even at -78 oC. This is partly for the high concentration of the anion centers.
• The degree of polymerization
0
0
I
MKxn
• K=1 or 2 depending on initiator used.
Characteristics of an Ideal Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Initiation by Electron Transfer
- .
- .
CH2 CH CH2 CH-.
CH2 CH-.
CH2 CHCH2CH--
+ KTHF
-78 oC
K +
K + + +
2
K +
K +K +K
+
• Polymerization mostly done in THF and not nonpolar solvents like cyclohexane or benzene for the solubility the complex in THF.
• The degree of polymerization is given by
0
02
I
Mxn
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Initiation by Nucleophilic Attack
CH2 CH CH3(CH2)4 CHCH3(CH2)2CH2 Li Li
COOCH3
CH2 C
CH3
N Li N
COOCH3
CH2 C
CH3
Li
THF
-78 oC+
++
THF
-78 oC+ +
• Polymerization can be done in both polar and nonpolar solvents.
• The degree of polymerization is given by
0
0
I
Mxn
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Initiation by Living Polymer
CH2 CH Li CH2 C
CH3
COOCH3
CH2 CH CH2C
CH3
COOCH3
LiTHF
-78 oC++ +
CH2 CHLiCH2 C
CH3
COOCH3
++
Because the starting anion has to be a stronger Lewis base than the resulting anion.
But not
0
0
I
Mxn
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Propagation
M Z M M MZ+-Z+-
Z+- +CovalentBond
Contact IonPair
Solvent SeparatedIon Pair
Free ions
Solvent polarity increases
kP increases
Polymer tacticity decreases
• Kp can vary by orders of magnitude.• The polydispersity remains low because the rate of
inter-conversion between the different forms is much faster than that of polymerization.
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Termination
M MH
M MCOO
MCH2Br CH2Br
MM
MCH2Br CH2Br
M Br
Z+-
By proton
H+
Z+ +
By CO2
Z+- CO2
Z+-
By using a limiting amount of 1,2-dibromoethane
Z+-2
K=2
By using a much excess of 1,2-dibromoethane
Z+-
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
(1) proton donor H2O or ethanol Strong base is not enough for initiation.
(2)
Ctr,s=10-3 (small chain transfer constant)
EtOH high MW product
ethoxide no longer living.
Strong base is not enough for initiation.
C H 2 C
H
: - + H 2 O C H 2 C H 2 + O H
-
H2O Ctr,s=10H2O low MW polymer No living polymer
CH2 C
H
:- + C2H5OHCH2 CH2
+ C2H5O-
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
(3) Termination can occurred by hydride elimination without impurities.
a)
b) anionic species(active center) react with chain endsto form inactive allylic anion.
C H 2 C H C H 2 C H : - N a +
C H 2 C H C H C H
+ N a + H - :
C H C H C H 2 C H + C H 2 C H . . -
C H 2 C H 2 + C H C H C H 2 C H . . -
1,3 diphenylallyl anion very unreactive, highly resonance stabilized
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
Termination of polar monomer
In this case, although initiator or active center attack monomer, that means non-polymerization.
C H 2 C
C H 3
C O C H 3
O
+ R - L i + C H 2 C
C H 3
C R
O
+ C H 3 O - L i +
+ CH2 C
CH3
COOCH3
CH2 C:-CH3
COOCH3
Li+
CH2 C
CH3
COOCH3
C
O
C
CH3
CH2 + Li+CH3O-
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
Backbiting or intramolecular rexn
4) Hugginson-Wooding System
J.Chem. Soc. 1952
Polymerization of styrene conducted in liq. NH3 at bp -33C
(1) reaction rate ↑ as [I] and [M]2
I=K+NH2- rate ↑ as [NH2
-] ↑ but as [K+] ↓
(2) MW [K+] and [NH2-]
(3) Polymer is formed without unsaturation.
Cyclic trimer at the end of chain
C H 2 C C
O C H 3 O
C C H 3
C O O C H 3
C H 3 C O O C H 3
C H 2 C C
O
C C H 3
C O O C H 3
C H 3 C O O C H 3
+ C H 3 O - - ̈
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
][
]][[]][[ 2
2
K
KNHMKkMHNkR i
ii
N H 2 - C H C H 2 +
ki H 2 N C H 2 C : -
H
][
]][[
2
2
KNH
NHKk
KNH2 K NH2
k
[K+] 를 가하면 Ri
Dissociation of initiator
Initiation step
Hanyang Univ.Hanyang Univ.
Spring 2006
Propagation
Anionic Polymerization
]][[ MMkR pp
H 2 N M n - + M H 2 N M n . M
- kp
Termination
][
][][
]][[
][][
3,
22
3,
22
NHk
NHMkk
NHKk
KNHMkkKR
str
pi
str
pip
][
][][
]][[
3,
2
1
222
1
2
1
22
1
NHk
KNHMkKkR
KNHMKkR
str
pip
ii
H 2 N C H 2 C H C H 2 C : - H
+ N H 3 H 2 N C H 2 C H C H 2 C
H
H
: N H 2 - +
ktr,s
n n
Occurs by chain transfer
Rtr=ktr,s[M-][NH3+]Overall Rate using Steady state assumption. (RiRt).
KCl 을 넣으면 ? Rp slow down
[K+]=[NH2-]
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
][
][
][
][
33, NHC
M
NHk
MkX
sstr
pn
물이 없으면 ,
Chain transfer constant for solvent
molekcalEEEE
rateoverall
RateDPtemp
molekcalEEE
trpiR
n
trpnx
/9
/4
Activati on energy for Xn
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
1 1
1 n
wn
nn
w
M
MX
XM
M이면이므로
RONa + nCH2 CH2
O
CH2CH2O-Na+RO(CH2CH2O)n- 1
Flory 가 지적하기를
정지반응이 없게 되면 narrow MW distribution 을 얻을 수 있다 .
5) Base Initiated Polymerization
NO2 C O> > SO2 > CO2
>>> CH3CH CH2
CN > SO > C2H5
치환기들이 매우 중요 . 결국 nucleophilic substituents 의 electron withdrowing substituents 가 initiator 들에 가장 반응성이 좋음 .
2-nitropentene 등은 KHCO3 (potassium bicarbonate) 같은 것들에 의해서도 개시됨 .
–NO2 는 매우 e- withdrawing 해서 anion 을 안정화시킴 .
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
6) Practical Comments
If we use metal as an initiator propagation rate is fast.
purity import!
7) Propagation Kinetics
]][[ MMkR pp
라디칼 중합에 비해 propagation 은 그다지 빠르지 않음 .
많은 living polymer 들에 대해 [M:-] = [I][M] = is about 10-9 to 10-7 molar[M:-] = 10-3 to 10-2 molar
kp for free radical case is 5103 l/molesecKp 는 solvent 와 counter ion 에 dependent!solvent 를 변화 시키므로 해서 counter ion 을 active center 와 분리시킬 수 있다 .rate 상승을 기대 .
conc. of anion = conc. of initiaor
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
(1) Evaluatation of Individual Propagation Rate Constants
Propagation rate constant for free ion and ion pair. [P-]:conc. of free ion [P-(C+)]: conc. of ion pair
])][([]][[ MCPkMPkR ppp
2
1
)])([(][
][][
]][[
)]([1
)(
]][[][
)]([][
CPKP
CP ion
CP
CP
K
CPKCP .Eqat
MMkRM
CPkPkk app
pppapp
p
첨가하면더을만약
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
* How to measure kp, kp, K ?
][
log 0
MC
C
.apppkslope
appk
2
1
][ M
p
pp
kintercept
Kkkslope 2
1
)(
t
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
][
][][
C
MKP
][][
][CZ
MKP
Conc. of living and conc. of free ion
][][
][)]([CZ
MKMCP
A salt that must be soluble in THF with common ion to gegen ion is added to reaction mixture.
[C+][CZ]
At high added salt conc.
Conc. of added salt is [CZ]
][
)(
CZ
Kkkkk pp
pappp
][
)]([][
M
CPkPkk
originally
pappp
apppk
][CZ
p
pp
k
Kkkslope
int
)(
Now
Then able to get kp-, kp
, K from two graphs.
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
Effect of gegen ion on Anionic Polymerization of Styrene
THF Dioxane
kp K107 kp
- kp
Li+ 160 2.2 6.5104 0.94
Na+ 80 1.5 3.4
K+ 60~80 0.8 19.8
Rb+ 50~80 0.1 21.5
CS+ 22 0.02 24.5
- Why kp- is the same value?; kp- is much more larger than kp Thus we can say that reactivity of free ion is much greater than that of ion pairs.
- In the case of dioxane?;In dioxane which is not tend to be solvating it has reverse tendency compared to the case of THF. Solvation is not important in dioxane. Cs is too big that there is no difference. Explanation is that there is not so solvating power of Cs
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
]][[
]][:[
MRLikR
MLiMkR
ii
pp
Look at difference.Unassociated species
Li+ genenion in aromatic hydrocarbon
Let’s say we are using BuLi initiator.
결국 solvation as well as is important!
1,2 diethoxyethane 은 을 낮추게 되지만 highly solvating ether 이므로 kp varies 1~1000 fold. Sty in THF, free ion 의 역할이 큼 . Reactivity of free ion 이 ion pair 의 reactivity 보다 큼 .
In aromatic hydrocarbonUnassociated species dominate rate. 이전의 경우는 free ion 이 속도를 결정했으나 이 경우는 unassociated species 만이 속도를 결정한다 . (very low conc.)
(nC4H9Li)6 C4H9Li6
K1
(R Mn-Li+)2 2C4H9 Mn-Li+K2
CH2 C
H
RLi
LiCH
RCH2 2 CH2 CLi
H
RCovalent character
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
6
1
6946
1
1 ])[(][ LiHCKRLi
rateinitiationinorder
Rtheinorder
LiMKLiM
R i
6
12
1
2
1
22
1
2
6
1
]):[(]:[
][
Evidence — viscosity measurement before and after term we find that living
polymer is associated after termination, viscosity drops.
고분자 혼합물에 개시제를 가하면 Ri 는 1/6 승에 비례하게 된다 .
Aliphatic HC 내에서의 중합반응은 aromatic HC 내에서 보다 훨씬 낮다 .
왜냐하면 개시제와 ion pair 들의 dissociation 이 적어지기 때문 .
Hanyang Univ.Hanyang Univ.
Spring 2006
Effect of solvent and gengenion on Copolymerization of Styrene and isoprene at 25 C
Solvent% Styrene in copolymer
Na+ counter ion Li+ counter ion
Nonsolvent 66 15
Benzene 66 15
Triethyl ether 77 59
Ethyl ether 75 68
THF(highly saturating solvent)
80 80
일반적으로 sodium이 lithium 보다 더 ionic 함
@ Li+ 이 Na+ 보다 active center 에 더욱 tight 하게 결합되어 있음 . Solvating solvent 는 Li+ 의 경우는 변화 시키고 부분적으로 ionic 한 Na+ 은 많이 변화 시키지 못한다 .
Lenz P.437 Table 13-9
Anionic Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
St-MMA System
1) Li Metal Initiator 를 쓸 경우 고분자 생성물에 Styrene 이 많이 포함 .2) BuLi 개시제를 쓰면 Styrene 이 거의 없음 .
Old Explanation
1)Radical anion mechanism 으로 설명2)Li metal 을 사용하면 MMA 와 Styrene 이 중합3)MMA 는 anion 으로 형성4)Styrene 은 radical 이 형성되어
New Explanation Overberger, 1966
NMR 을 사용 , styrene block 을 발견Radical 은 발견못함처음에 styrene block 이 형성 , MMA 블록은 나중에중합초기에 Li counterion 이 Li metal 에 용해 , 중합이 homogeneous 하게 진행된다 .
MMM SS MSMMS MS MMM SS M
Hanyang Univ.Hanyang Univ.
Spring 2006Anionic Polymerization
CH=CH2
C=O
OMe
C
CH3
CH2
Li
즉 styrene 이 Li particle 과 associated 됨 .
St 이 MMA 를 Li 에 못가게끔 blocked out 시킴 . Sty 이 표면에 강하게 흡착된 후 고분자가 선택적으로 형성
성장사슬이 점차 medium 인 (solution) 에 용해되어 결국 Li particle 을 뚫고 나와서 solution 으로 나옴 .
Li soluble
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
C CH2
H3C
H3C CH2 CH
OCH2CH3
proton donorelectron acceptor
δ- δ-
Positively charged active center 에서 중합반응이 일어남alkene 류의 모노머에서 중합이 일어나는 경우 electron donating 치환기를 갖는다 .
예 )
isobutylene ethylvinyl ether
1. protonic acids : HCl, H2SO4, HClO4, Cl3CCOOH 2. Lewis acids : BF3, AlCl3, TiCl4, SnBr4, SbCl3, BiCl3
Initiators– 주로 Acids
B
F
F
F
C2H5Cl C2H5 [BF3Cl]+. .
. .: +
C2H5 [BF3Cl] + C2H5 CH2 CH [BF3Cl]
R
CH2 CH
R
+ ++ .
이 경우를 cationogen 이라 함
Electron donating group
* Lewis acid 는 개시제로 효과적으로 사용되기 위해 coinitiator( 공촉매 ) 를 사용한다 .
chloroethane
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
OH
BF3OH H++ C C
C
C
CH3 C+
C
C
B F3OH
isobutylene
BF3 + OH2 BF3OH H+k e
CH3 C C C C+BF3O H + C C
C
C
kp
Typical Initiator Systems Co-initiator Initiator SnCl4 H2O AlCl3 HCl H2SO4 H2SO4
Order of reactivity AlCl3 > AlRCl2 > AlR2Cl >AlR3 물이 있고 공기중에서 spill 하면 불남
HCl > CH3COOH > C6H5NO2 > > H2O >> CH3OH > CH3COCH3
Ex)
More acidic initiators are most effective in initiating polymerization
Hanyang Univ.Hanyang Univ.
Spring 2006
Termination
Kinetics
Cationic Polymerization
Second order 이므로 반응이 매우 빠름 2 *
3
*
2t
eipp M BFOH
k
KkkR
C C C
C
B F3OH
C
C
C
+ HB-F3OH
H
32ei3ii BF OH MKkHOFBH MkR
OHBF MkR 3pp
S SRR ti 32ei3tt BF OH MKkOHBF kR
32t
ei3 BFOHM
k
KkOHBF
문제 : 정지반응이 random 하게 일어난다 .
* 가 recipe 임 , 반응을 조절할 수 있음
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
MXkconstXk ntrnt 0,. 0 이면이면
Mkk
MkX
trt
pn
만약
C1
C3
C 6
C7
C8
C15
C16
B17
F3OHk tr
C21
C22
C27
C30 C 32
C33
C34
B F3OH+
M k k
M k
RR
RX
trt
p
trt
pn
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
1) Ring opening polymerization
(1) Mechanism
carbon type polymzn. 이러한 ROP 를 할 수 있는 monomer 들로는 cyclic amides, sulfides, acetals, esters, lactam, alkanes, …
(2) 중합가능성
Polymerizability 는 안정하지 않은 ring 또는 쉽게 cyclize 하지 않는 ring 이 잘 됨 .3,4 and 7-11 membered ring 이 가장 reactive 하다 . 5,6 membered rings are stable
and slow 중합 . 그러나 중합은 가능함 .3-membered ring most easily polymerize
O R CH2 OCH2
R
O
CH2
ROORCH2ORCH2
CH2
R
++
+. .. .
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
(3) THF(Polytetrahydrofuran) 의 중합예
PF52 PF4 (PF6)+ -
PF4 (PF6)+ - + O PF4 O
+PF6
-
gegenion
O(CH2)4O(CH2)4 O(CH2)4
(CH2)4
+-
AO
O(CH2)4O(CH2)4O(CH2)4
+O (CH2)4
+
-A
cocatalyst 로 H2O 가 존재하면 중합속도를 증가시킴 .living polymrization 이 가능하나 termination 이나 transfer 도 일어남 .
O (CH2)4 O+
-A+ O
(CH2)4
(CH2)4
Hanyang Univ.Hanyang Univ.
Spring 2006Cationic Polymerization
(4)Kinetics
I + ZY K Y+(IZ)
-
initiator coinitiator
Y+(IZ)
-+ M
ki YM+(IZ)
-
nM O+
+ O Mn O (CH2)4O
CH2 C+
H
R
[SnCl4OH]- + CH2 CH
Rstrong initiator
CH2CHCH2
R
]][][[]][)([ MZYIKkMIZYkR iii
]][[ MMkR pp
Initiation
예 ) styrene, stannic-chloride-H2O System [SnCl4OH-]H+
Propagation – can have a low activation energy and be rapid
or
Simple propagation reaction
Overall rate of polymerization may actually increase w/ decreasing temperature, means that termination has a high activation energy.
Top Related