Chemistry Reference
In-Depth Information
More recently, McCullough and coworkers [
73
] reported using the Grignard reaction to synthesize
poly(3-dodecyl thiophene)
C
12
H
25
Br
Br
Br/H
S
1.RMgCl
Br/H
2. Ni(dppp)Cl2
n
C
12
H
25
C
12
H
25
The molecular weights of the products were found by them to range from 10,000 to 50,000.
Earlier, McCullough et al. [
74
] reported that they have developed an end group functionalization
method that enables the synthesis of many well-defined block copolymers that form nano wires with
high electrical conductivity. They claim to have discovered that nickel-initiated regioregular poly-
merization of alkyl-thiophenes proceeds by a chain growth mechanism. They also observed that the
degree of polymerization of poly(alkyl-thiophenes) increases with conversion and can be predicted
by the molar ratio of monomer to nickel initiator. On the basis of their experimental results, they
concluded that nickel-initiated cross-coupling polymerization is essentially a living system, with low
polydispersities.
Irvin et al. [
75
] reported forming a poly(3,4-difluoro thiophene) by anodic polymerization:
S
S
Si
Si
n
F
F
F
F
Because of the very electron-poor nature of the monomer, electro deposition could only be
accomplished with a strong Lewis acid, BF
3
EtO.
Mendez and Weder improved considerably the conductivity of poly(3,4-diethylene, dioxy-
thiophene) by cross-linking [
76
]. The polymers were oxidatively synthesized in the presence of
four different oxidative cross-linkers,
S
S
S
S
S
S
;
;
S
O
C
8
H
17
S
S
O
C
8
H
17
The cross-linking compounds were incorporated into the polymer in amounts of 0.5-2%. As a
result, in a maximum case, the conductivity increased by as much 36%.
