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Conjugated Polymers and Carbon Nanotubes for Optoelectronic Applications
Liming Dai
Department of Polymer EngineeringCollege of Polymer Science and Polymer Engineering
The University of Akron, Akron, OH 43325-0301
In close collaboration with
Richard A. Vaia
AFRL Materials and Manufacturing DirectorateBldg 654, 2941 P St. Wright-Patterson AFB, OH 45433-7750
Collaborative Center for Polymer Photonics Workshop at Akron, April 22-23, 2004
Important Discoveries
1977 Conducting Polymer by Heeger, MacDiarmid, Shirakawa
1985 Fullerene C60 Curl, Kroto, Smalley
1990 Conjugated Polymer LEDs by Friend et al.
+
n
e.g.
1991 Carbon Nanotube by Iijima
Requirements for Polymers to be Electrically Conducting
Just like metals have high conductivity due to the free movement of electrons through their structure, for polymeric systems to be electronically conductive they must possess:
a) Charge carriers (Doping)
b) An orbit that allows the charge carriers to move (Conjugation)
-e
-en-
dopi
ng
p-do
ping
+e
+e
Iodine-Induced Conjugation of Polydienes
Dai, L. et al, Macromolecules, 1994, 27, 6728.
R1
(IV) Pale-yellow, orange or dark brownHH R2
+ I 2CH2 C C CH2 CHCCCH CCCH2
CH
+HI
CH
I
(2)-HI
CH2 C CCH C C CHCH2CCCH2
I
(II) Colorless
I
I
I
I
I
I
CH2 C C CH2 CH2CCCH2 CH2CCCH2
(1) +I2
CH2 C C CH2CH2 C C CH2CH2C
(I) Colorless
(III) Pale-yellow, orange or dark-brownI
R1
R2
R1
R2
R1
R2
R1 R1
R2
R1 H
R2
R1
CCH2
R2 R2
R1
R2
R1
R1 R1
R2
R2 R2
R1 , R2 refer to either H or CH3 group.
(3)
CH2
C C
H
CH2
H
CH2
C C
H
CH2
H
CH2
C C
H
CH2
H
UVCH2
C CH
H
H
C C
H
CH2
CH2
CH2
C C
H
CH2
H
CH2
n
(a) Cis-1,4-polybutadiene
n
(a) Trans-1,4-polybutadiene
Micropatterning of Conducting Rubbers
Dai, L. et al., Macromolecules 1996, 29, 282.
(a)
(b)
HOMO
hv
LUMO
intrachainphotoexcitation
luminescence
singlet excitonradiative decay
singlet excitonradiative decay
(-)polaron (electron injection)
e-
cathode
hv'
anode (+)polaron (hole injection)
The Principle for Polymer Light-Emitting Diodes
Colour Tunability of the Light-Emitting Polymers
O
O
O
O
n
m
450 500 550 600 650
( D )( C )( B )( A )
Wavelength ( nm )
OO
O
O
O
O O
O
O
O
O O
O
O
O
n/2
CHO
OO
OCH3O
O
O
O
OCH3
O
O
O
CH3O
O
O
O
OCH3
O
O
O
CH3O
O
O
O
OCH3
O
O
O
CH3O
O
O
O
OCH3
Patterned and Multilayered Light Emissions
Confined Space for Colour Tuning
B. Winkler et al., J. Mater. Sci. Lett. 1999, 18, 1539.
Heeger, et al, Science 1995, 270, 1789.
MEH-PPV-C60 blends
Conducting Polymer Plastic Solar Cells
Iodine-Induced Conjugation of C60-Grafted Polydienes
CH CR CH CH2 CH2 CR CH CH
CH CR CH CH2 CH2 CR CH CH
Li+ Li+
H H
CH2 CR CH CH2 CH2 CR CH CH2
CH2CR CH CH2 CH2 CR CH CH2
Li
C60
MeOH
Sec-BuLiTMEDA
( R=H or CH3; =polydiene segments )
Dai, L. et al., J. Phys. Chem. 1995, 99, 17302.
CH CR CH CH2 CR CH CHH H
CH2
CH CR CH CH2 CR CH CHH H
CH2
I
I
I
I
C CR CH CH CR CH CH H
CH
+ I2
- HI
Sulfonated C60/Dendrimer-Doped Polyaniline
Dai, L. et al, J. Phys. Chem. 1998, 102, 4049.
OSO3H
OSO3HHO3SO
OSO3H
HO
HO
HOOH
OH
OH
OSO3H
HO3SO
SO3HSO 3
HSO 3HS
O3H
HO 3S
HO 3S
HO 3
S SO
3H
HO
3S
HO
3S
SO
3 HSO
3 H
SO3 H
SO3 H
SO3 H
SO3H
SO3H
SO3H
SO
3HH
O3 S
SO
3H
HO3 SHO
3 SHO3 S
HO3 S
HO3S
HO3S
HO3S
SO 3H
HO
3 S
SO
3 H
SO3 H
N
N
N
N
H
H
H
H
-O3 S
SO 3- n
Optoelectronic Properties of the Sulfonated C60-Doped Polyaniline Film
Dai, L, et al., J. Phys Chem. 1998, 102, 4049
Optical Limiting by C60-Ag Nanocomposites
Sun N., et al., Chem. Phys. Lett. 2002, 356, 175.
Optical limiting responses to 8ns, 532 nm optical pulses, HDTC60–Ag (square), DT–Ag (circle), and HDTC60 (triangle).
Polyaniline Nanotubes
Qiu, et al. Macromolecules 2001, 34, 675.
PANI-(CNT- OSO3H)PANI-(C60-OSO3H)
Wei, et al. Adv. Mater. 2003, 15, 136.
Conducting Polymer Micro-/nano-structures
Bajpai, et al. Adv. Funct. Mater. 2004, 14, 145.
Potential Applications of Conducting Polymer Micro-/nano-structures
-1.2 -0.8 -0.4 0.0 0.4 0.8 1.2
b
a
-20
-10
20
10
0.0I (m
A)
E (V vs. Ag/AgCl)
460 480 500 520 540 5600
4
8
12
(c)
(b)
(a)
Ind
esi
ty (
a.u
)
(nm)
Field emission of polymer micro containers on gold substrate
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2
E (V/m)
I (A
/cm
2)
Gold
Micro containers on Gold
Carbon Nanotube Electron-Emitting Displays
Courtesy of Y. Saito
Pyrolytic Growth of Aligned Carbon Nanotubes from Metal-Organic Complex Molecules
NN
NN N
NNN
M
Huang, et al., J. Phys. Chem. B 1999, 103, 4223.
Huang & Dai J. Nanoparticle Res. 2002, 4, 145.
The Growth Process for Aligned Carbon Nanotubes