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Substantially Conductive Polymers. Part 03. Synthesis. Possible Polymerization Mechanism of Acetylene (via the metal-carbene intermediate). metallocycle. metal-carbene. Insoluble Infusible Intractable. Solubility Improvement of Polyacetylenes (via incorporation of substituents). - PowerPoint PPT Presentation
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Substantially Conductive Polymers
Part 03
SYNTHESIS
PossiblePolymerization Mechanism of Acetylene(via the metal-carbene intermediate)
3
HC CHWCl6 / Bu4Sn
polyacetyleneacetylene
WCl6 CH3CH2CH2CH2 WCl5
Bu4Sn Bu3SnCl
Bu4Sn
Bu3SnCl
CH3CH2CH2 C
WCl4
H
H
H3CH2CH2CH2C
CH3CH2CH2CH3
"Metal carbene"
C WCl4CH3CH2CH2
H
HC CH
C WLnH7C3
H
HC CH HC
CH
CH
WLn
H7C3
HC CH
C WLn
C3H7H
HC CH
C
C
H C3H7
H CH
WLnC
CH
HHC C
CH
C3H7
WLn
C
H
CH C3H7
H
CC
C
C3H7
H
H
HHC
HC WLn
HC CH
etc.WLn
H
terminationPolyacetylene
InsolubleInfusibleIntractable
metallocyclemetal-carbene
Solubility Improvement of Polyacetylenes (via incorporation of substituents)
RC CHWCl6 etc. etc.
R R R R RT. Masuda et. al. with improved solubility
WCl6 + C6H5C CH + etc.
PhPhPh
etc.
1 x 200
C. C. Han & T. J. KatzOrganometallics 1982, 1, 1093Organometallics 1985, 4, 2186
Olefin Metathesisring-opening polymerization
WCl6 + PhC CH etc. WLx
PhPhPh
etc.LxW
PhPhPhPhPh Ph
W
etc.
PhPhPh
WLxetc.
PhPhPh
WLx
H
4
Coplanarity is the key for gaining high conductivity
Substituent Effects: Solubility Conductivity
5
full overlaping
Coplanarity gives best overlapingbetween orbitals
Distortion from coplanarityreduces the electron mobility
partial overlaping
no overlaping
90o distortion lead to conjugation defects
doped with I2
R R R R RR = Me, Br, Cl ......... etc.doped with I2; < 0.001 S/cm> 10 S/cm
Steric hindrance effect of substituent is very important
Because,R group destroy the coplanarity of the conjugation systemReduce electron mobility of intrachain and interchain
Alternative Methods for Making Polyacetylenes
17
Cl Cl Cl Cl Cl - HCl¡µ
pyrolytic eliminationPVCpoly(vinylchloride) C. S. Marvel et. al. JACS, 61, 3241 ( 1939 )
Cl2Cl
Cl
Cl
Clpoly(1,4-butadiene)
- HClKNH2 / NH3 (liq)
East German patent 50, 954 ( 1966 )CA 66 : 86117 r
Cl Cl Cl Cl Cl Cl
conjugation defects
Both approaches yield poorly conductive polyacetylenes
Dehydrochlorination
Durham Route (via a processable precursor)
18
X X Ring-openingolefin metahesispolymerization
X X
n
retro-cyclization
X X
n
I2doping 10 S/cm
+
Cyclization
t1/2 ¡Ü 20 h at 20 oC
very unstabledifficult in handling
10-7 S/cm¡î too much " stability gain "
both products form conjugated systems
(X = -CF3, -COOMe)
Cyclooctatetraene
XC CX
Feast et. al.1. Polymer, 21, 595 ( 1980 )2. J. Phys. Colloq. C3, Suppl. 6, 44 : C3 -148 ( 1983 )3. Polymer, 25, 395 ( 1984 )
X
XX
X
19
The Diels–Alder Reaction(1,4-addition reaction; concerted reaction)
8.8
7-45.ppt
+
new bond
new bonddiene dienophile transitionstate
a pericyclic reaction; a [4+2] cycloaddition reaction
3 2σ+ 1
20
ROMP
nn
£G
70 oC
stable at RTeasier in handling " less stability gain "
Resonance Energy (Kcal/mol)
3660
Strategy : Stabilize the prepolymer by reducing the stability gain in the conversion step
X X
n
retro-cyclization
X X
nt1/2 20 h at 20 oC)unstable at RT
For the 2nd ring:24 kcal/mol
Syntheses of Poly(p-phenylene) (PPP)
21
Cl Cl + Nan
+ NaCl Wurtz -Fittig Reaction
G. Gold finger et. al. J. Polym. Sci., 4, 93 ( 1949 )J. Polym. Sci.,16, 589 ( 1955 )
I I
R
+ Cu
R
nUllmann reaction
S. Ozasa et. al. Bull. Chem. Soc. Jpn., 53, 2610 ( 1980 )• Had very low molecular weights or irregular structures
Cl Cl + Na Cl Cl + Na
ClCl Cl + NaCl
NaCl
Cl Cl
or
Cl
Cl Cl
Cl
Reductive polymerization (step-reaction)
22
I I
R
+ Cu I CuI
ROxidativeaddition
I CuI
R
I Cu
R
I
R
+ CuI2
Reductiveelimination
I
R
I
R
etc.
R R
etc.
R RR
23
+ CuCl2 / AlCl3n
P. Kovacic et. al. JACS 85, 454 ( 1963 )
Most successful and economicalOxidizing agent : CuCl2, MnO2, MoCl5, FeCl3Lewis acid catalyst : AlCl3, AlBr3
CuCl2
AlCl3Cl Al
Cl
ClCl + CuCl
Radicalcation
H
HAlCl4
AlCl3CuCl2
- 2H+2 HAlCl4+CuCl
Use of AlCl3 help reduce the following side-reaction
+ Cl ClH
+ CuCl + Cl- H
CuCl2Cl
Oxidative polymerization (step-reaction)
23
24
n n
Ziegler catalyst
MW = 5000 - 10,000poly(1,3-cyclohexadiene)
450- H2
£G
¢J
chloranilxylene
C. S. Marvel et. al.JACS 81, 448 ( 1959 )J. Polym. Sci. A3,1553 ( 1965 )
aromatization
OCl
ClO
Cl
Cl
p-chloranil
( tetrachloro-1,4-benzoquinone )
Oxidant
n n n( Cl2, Br2 )
300 - 380
- 2 HX- H2
n
- H2
X2 ¢J
£G
X X
-2 HX
Catalyzed Chain polymerization
n n
450 ℃chloranil
xylene aromatization
- H2 n n
300 - 380
- 2 HX- H2
℃X X
25
HO OH HO OHpseudomonas putida
Base
C
O
Cl R
O O CC ROO
R
R = OCH3, CH3, Ph
( for improving solubility )
O O CC RROO
n radical chainpolymerization
highly soluble ; easily processibleDP = 600-1000 ( degree of polymerization )
220 ℃n
( t1/2 = 30 sec for R = OMe)
Ballard et. al. JCS, CC 954 ( 1983 )
Lower the aromatization temperature via the decarboxylation
26
Free Radical Chain Reaction
OR
OCORROCO
ROOR
Initiation step
OCORROCOOCORROCO
RO
Propagation steps
RO
R' R' R' R'
( R' = OCOR)
TerminationR' R' R' R'
RO
R' R'n
(X = radical terminator)
X
Syntheses of Polyphenylene Vinylene (PPV)
H3C CO
HCH CH
n
(CH3)3C O K
DMF
G. Kossmehl et. al.Makromol. Chem. 182,3419 ( 1981 )
H2C CO
HH
B
H2C CO
H
H
C C
OH
HH
H n
- H2OCH CH
n
C COH
HH
H
Nu
C COH
HH
HC C
OH
HH
HNu C C
OH
HH
Hetc.
C COH
HH
HC C
OH
HH
HC C
OH
HH
H
C COH
HH
HCH
Hetc. etc.
or
30
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