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