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OU
TLIN
E
Lect. 2:
Synthetic Methods toward Organic Semiconductors
Lect. 1:
Organic semiconductors: Bandgap Engineering.
Organic Semiconductors
Poly(Phenylene Vinylene) (PPV)
n
OC1C10-PPV
O
O
n
Sn
RR-Poly(3-HexylThiophene) (P3HT)n
H17C8 C8H17
Poly(DiOctyl-Fluorene) (PDOF)Plastic Electronics
Applications as Semi-Conductor
(MDMO-PPV or OC1C10-PPV or MEH-PPV) and conjugated polymer
Workhorse materials in plastic electronics
(LBG or low bandgap or low band gap) and conjugated polymer
Workhorse materials in plastic electronics
Synthesis of Conjugated Polymers
N
SN
S S
n
Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-CycloPenta[2,1-b;3,4-b′]-
DiThiophene)-alt-4,7-(2,1,3-BenzoThiadiazole)]
PCPDTBT
Material Specifications
Low Defect Level in Conjugated System
High Mobility of Charge Carriers
Appropriate Electrochemical properties ( Eox
and Ered)
High Thermal Stability of the Conjugated System
(some cases) Supramolecular Order
Elektronic Specifications
Simple Monomer Synthesis
Straightforward polymerization chemistry
Processible from common solvents
Sufficient High Molecular Weight ( Mn > 25 000 )
Reasonable polydispersity (1 < PD < 3)
High Thermal Stability
Polymer Specifications
Material Specifications
Purification and fractionation
Recycling GPC
Wataru S. et al. Org. Biomol. Chem., 2014, 12, 3354–3357
Scalability of the synthesisPo R. et al., Macromolecules (2015), DOI: 10.1021/ma501894w
Synthetic Complexity
nPPV
O
O
BrBr
+
CHO
CHOP(C6H5)3Cl
P(C6H5)3Cl
+
McMurry Reaction (TiCl4/Zn,THF)
Heck Reaction
Wittig Reaction (Base)
(Pd(OAc)2/Base)
Synthesis of PPV
XC8H17H17C8X
HOOC COOH
S
XC8H17H17C8X
S
S
XC8H17H17C8X
O
S
XC8H17H17C8X
O OH
S
XC8H17H17C8X
OO
O
XC8H17H17C8X
OO
X = S (a), O (b)
O
O
14 15 16
OHHO
MeOOC COOMe
OC8H17H17C8O
MeOOC COOMe
vi
ClCl
HOOC COOH
SC8H17H17C8S
EtOOC COOEt
9 10 11
17a,b 18a,b 19a,b
20a,b 21a,b 22a,b
13
OTMSTMSO
MeOOC COOMe
iii
ivTMSO OTMS
v
12
ClCl
EtOOC COOEt
i ii
vii viii ix
x xi xii
S
SC8H17H17C8S
n
Low Band Gap Conjugated Polymers
Outline part 2
Direct synthetic routes
Oxidative polymerization
McCullough method
Rieke Method
Suziki coupling
Stille and Sonogashira coupling
Yamamoto Coupling
Precursor routes
Oxidative Polymerization
S
FeCl3, CHCl3
Sn
Ar
Ar
NC
CN
n
OC
10H
21
H21
C10
O
Ar
Ar
NC
CN
OC10
H21
H21
C10
O
S S
OO
S
C8H
17
S
OO
C14
H29
Ar =
FeCl3
CHCl3
a b c d
5 6
SBr Br
R
SBrZn Br
RNi(dppe)Cl2
b.
Negishi Coupling
> 98% Regioregular
SBrMg Br
R
SBr
R
Ni(dppe)Cl2
S
R
n
a.
Kumada Coupling
Poly(Alkyl Thiophene) (PAT)
S
R
SS
e
R
F Cl3S S
R
S
R
R
S
R R
75%
25%
a. McCullough R. D., Lowe R.D.; J. Chem. Soc. Chem. Commun., 70 (1992)
b. Chen T-A., Rieke R. D.; J. Am. Chem. Soc., 114,10087 (1992)
Regio-Regular Conjugated Polymers
Nobel prize 2010
Chemistry
Mechanism of cross-coupling
R MMX
Reductive elimination
heterocyclic sp2
carbon atom
oxidative addition
transmetalation
R
Pd X
Pd R
XPd(0)
I. Osaka and R. D. McCullough, Acc. Chem. Res., 41, 1202-1214 (2008)
E. L. Lanni and A. J. McNeil, J. Am. Chem. Soc. 131, 16573-16579 (2009)
Regioregular P3ATs
GPC (MW vs PS) 1H-NMR UV-Vis DSC
m Yield
%
Mn
/103
Mw
/103
PD RR lmax / nm
(CHCl3)
Tm /
°C
(peak)
3 - - - 96.1 290
4 75 19.5 44.7 2.29 96.5 281
5 79 16.7 32.3 1.93 94.5 451 249
6 80 23.7 42.6 1.80 94.5 450 234
7 67 24.4 39.9 1.64 97 451 198
8 73 28.0 46.5 1.66 97 451 210
9 50 25.9 37.8 1.46 98 449 187
S
CmH2m + 1
n
**
P3mT
‘P3HT’
= P36T
Rieke coupling
W. Oosterbaan et al., J. Mat. Chem. 19, 5424-5435 (2009)
Fiber formation & isolation
Example: 0.5 wt % P35T in p-Xylene:
1. Dissolve at 80 °C clear orange solution
2. Slowly cool to room temperature colour changes to dark red
3. Isolation by centrifugation
300 400 500 600 700 800
0.0
0.5
1.0
Norm
aliz
ed A
bsorb
ance
l / nm
Supernatant
Pristine dispersion
Fiber
AFM (tapping mode, 1 x 1 mm)
P34T
P39T
P33T
P37T
P35T
Fiber sizes:
Height: 5—10 nm
Width: 20 nm
Length: 0.5—4 mm
W. Oosterbaan et al., J. Mat. Chem. 19, 5424-5435 (2009)
Poly(p-Phenylene) Derivatives
Suzuki Coupling
n
B
OH
OH
B
HO
HOBrBr+
K2CO3
Pd(PPh3)4
nH17C8 C8H17
Poly(dioctyl-fluorene) (PDOF)
Nobel prize 2010
ChemistryM. Seki, Synthesis 18, 2975-2992 (2006)
Other cross-couplings
SBrBr
Pd(PPh3)4SSn(CH3)3(CH3)3Sn
+
n
S
S
Stille cross-coupling
Sonogashira cross-coupling
SBrBr
CuI, Pd(PPh3)4S+
nS
S
M. Seki, Synthesis 18, 2975-2992 (2006)
Other cross-couplings
Yamamoto cross-coupling
SBrBr
Ni(COD)2
nS
N. Blouin and M. Leclerc, Acc. Chem. Res. 41 (9), 1110-1119 (2008)
N
SN
S S
n
Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-CycloPenta[2,1-b;3,4-b′]-
DiThiophene)-alt-4,7-(2,1,3-BenzoThiadiazole)]
PCPDTBT
Low Bandgap Polymers?
Low Bandgap Polymers?
Bundgaard, E., Krebs, F. C., Sol. Energy Mater. Sol. Cells 2007, 91, 954
N
SN
S S
n
Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-
CycloPenta[2,1-b;3,4-b′]-
DiThiophene)-alt-4,7-(2,1,3-
BenzoThiadiazole)]
PCPDTBT
Outline
Direct synthetic routes
Oxidative polymerization
McCullough method
Rieke Method
Suziki coupling
Stille and Sonogashira coupling
Yamamoto Coupling
Precursor routes
PolyThiophene Derivatives
LBG Derivatives
Precursor Routes toward Conjugated Polymers
n
Poly(Phenylene Vinylene) (PPV)
T
Pn
O
O
nOH
O
O
n
Basic
Hydrolysis
Radical
Polymerisation
F3C CF3
ROMP
T
n
F3C CF3
+
n
T
F3C CF3
n
Precursor Polymers
Feast PA Precursor route
J.H. Edwards and W. J. Feast, Polymer, 21, 595 (1980)
n
Poly(Phenylene Vinylene) (PPV)
Gilch Route (1966)
H. G. Gilch, W. L. Wheelwright; J. Polym.Sc.; part A, 4, 1337 (1966)
ClClor THF
t-BuO in dioxane
nCl
Polymerisation Reactions of Para-Quinodimethane Systems
R
n
ClCl
S S
R
RR
RClCl
t-BuOK/THF NaOH/H2O
SCl
Cl
R =
Cl
Cl
S
R
R
Polymerisation Reactions of Para-Quinodimethane Systems
Synthesis
Precursor Routes - General Scheme
Gilch (1966): L = P = Cl
Wessling (1968): L = P = SR2+X-
Sulfinyl (1992): L = Cl ; P = S(O)R
Xanthate (1995): L = P = SC(S)OR
Dithiocarbamate (2003): L = P = SC(S)NR2
(PPV)[
]n
L = leaving group
P = polariser
PLp-QM
P
PL
p-QMP
STEP 2
Conjugated Polymer
P
[
]n
Precursor
STEP 1
STEP 3
1992
Sulphinyl Route (1992)
F. Louwet, D. Vanderzande, J. Gelan, J. Mullens; Macromolecules; 1995, 28, 1330
n
Poly(Phenylene Vinylene) (PPV)
SCl
R
O
t-BuO in sec-BuOH
S
R
O
T (70°C)
nS
R
O
Mw = 200.000; Yield = 80%
Polymerisation Reactions of Para-Quinodimethane Systems
Precursor approach
S n
Poly(2,5-Thienylene Vinylene) (PTV)
SiN
Si
Li
Lithium HexamethylDiSilazane
SS
N
SS
N
S SS
N
S
n
base
THF
H. Diliën et al., Macromolecules 43, 10231-10240 (2010)
Polymerisation Reactions of Para-Quinodimethane Systems
Highly versatile
S
OR
RO
N
RO
CN
CN
Cl
Cl
R
R
N
N
N
S
N
S
PNu
Anionic Initiation
1996
Polymerization Mechanism?
Pn
P
P
P
P
Radical Initiation
Polymerisation Reactions of Para-Quinodimethane Systems
L. Hontis et al., Macromolecules 36, 3035-3044 (2003)
I. Cosemans et al. , Macromolecules 44, 7610-7616 (2011)
44% 35%
Highly Reactive p-Systems
P. C. Hiberty, P. Karafiloglou; Theoretica Chimica Acta; 1982, 171-177.
Ortho and Para-Quinodimethane Systems
Conclusion
Several very reliable synthetic methods exist toward the synthesis of conjugated polymers
Typically they are versatile, give rise to acceptable Mw
Give rise to low defects levels in the chemical structure
In some cases efforts to avoid residues of catalysts is an issue
Purification of the resulting polymer is of great importance <=> materials should be used in electronics