Complex Fluids & Molecular Rheology Laboratory, Department of Chemical Engineering,

National Chung Cheng University, Chia-Yi 621, Taiwan, R.O.C.

Chi-Chung Hua (華繼中 ) at NCCU

Cheng-Kuang Lee (李正光 ) at Academia Sinica

Show-An Chen (陳壽安 ) at NTHU

Nanomorphologies in Conjugated Polymer Solutions and Films for Application in Optoelectronics:

Experiments and Multiscale Computations

Background

Typical procedures for fabricating PLED devices or polymer-based solar cells:

C.K. Lee and C. C. Hua, in Optoelectronics - Materials and Techniques, edited by P. Predeep (InTech, 2011), Chap. 10.

Conjugated Polymer vs. Commercial Polymer Solutions?

Atomistic Dynamics (AMD) Simulation

Simulation information and conditionsInitial chain configurations: all in parallel with the xy plane (not created by MC simulation )Force field: DREIDINGEnsemble: NPTSystem temperature: 298 K System pressure: 1 atmTime step: 1 fsTotal step: 100,000 (=100 ps)PC nodes and simulation time: 16 CPU, 28~30 hours

SystemNo. of chains

of monomer unitsNo. of solvents

Density（ g/

cm3）Figure (a)Figure (b)Figure (c)

PS (n=50) × 5MEH-PPV (n=20) × 5MEH-PPV (n=20) × 5

Cyclohexane × 1280Chloroform × 2000Toluene × 1152

1.400.900.99

The density was set to above, close to the normal pressure density at 298 K.

(b) MEH-PPV / Chloroform (c) MEH-PPV / Toluene (a) PS / Cyclohexaneca 70 Angstrom

4Hua, C. C.; Chen, C. L.;  Chang, C. W.; Lee, C. K.; Chen, S. A., J. Rheol. 2005, 49, 641. 

Parameter-Free, Predictive Multiscale Simulations

(1) Atomistic model & MD simulation

(2) Monomer model & CGMD/LD simulation

(3) Ellipsoid-chain model & MC simulation

(4) Bead-chain model & BD simulation

(5) Dumbbell model & BD simulation

Coarse-

graining

Coarse-

graining

Coarse-

graining

Linking

Quantum chemistry calculation

Shie, S. C.; Hua, C. C.; Chen, S. A., Macromol. Theor. Simul. 2007, 16, 111.

Shie, S. C.; Lee, C. K.; Hua, C. C.; Chen, S. A., Macromol. Theor. Simul. 2010, 19, 179.

Lee, C. K.; Hua, C. C.; Chen, S. A., J. Chem. Phys. 2010, 133, 064902.

Lee, C. K.; Hua, C. C., J. Chem. Phys. 2010, 132, 224904.

Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B 2009, 113, 15937. Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B 2008, 112, 11479.

Hua, C. C.; Chen, C. L.; Chang, C. W.; Lee, C. K.; Chen, S. A., J. Rheol. 2005, 49, 641.

Lee, C. K.; Hua, C. C.; Chen, S. A., Macromolecules, 2011, 44, 320–324

Lee, C. K.; Hua, C. C, Optoelectronics / Book 1,( InTech, ISBN 978-953-307-276-0)Lee, C. K.; Hua, C. C.; Chen, S. A., (to be submitted).

Coarse-graining (mapping) procedures

CG AMDbond B

CG AMDbend B

CG AMDtwist B

CG AMDvdw B

( ) ln ( )

( ) ln ( )

( ) ln ( )

( ) ln ( )

U r k T P r

U k T P

U k T P

U r k T RDF r

MEH-PPV PANI-EB

Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B 2008, 112, 11479.Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B 2009, 113, 15937

CG Model Potentials Constructed:

*

HN

NH

HN

NH

*

*

HN

NH

N

N

*

*N

N

N

N

*

(a)

(b)

(c)

PAN-LEB

PAN-EB

PAN-PNB

Single-Chain Statistics and Solvent Quality

(MEH-PPV) Single-chain properties computed by CGLD simulations

Snapshots (300-mer)

In ChloroformIn Toluene

2CM CM

211

MT

211

MC

Diffusivit

( ( ) (0))1lim

6

m7.51 10 ( )

s

m9.62 10 ( )

s

y:

t

tD

t

D

D

r r

1

p

p, MT

p, MC

65.1 11.8 (A

Persistant length:

)

73.3 12.5 (A)

nj k

k j

La

L

L

Q Q

Scaling Law

n : 26,000 ~ 130,000

:100 ~ 500

M

N

2

CM1

g

g,MT

g,MC

Radii of gyrati

3

o

4.4 0.7 (A)

43.7 0.5

n:

(A)

N

iiR

N

R

R

r r

Solvent quality

Lee, C. K.; Hua, C. C.; Chen, S. A., J. Phys. Chem. B 2008, 112, 11479.

Quenched-Chain Morphology vs. Memory Effect?

Number Ratio

CF 100% CF 75 % CF 66 % CF 50 % CF 33 % CF 25 % CF 0 %

Rg (

An

gs

tro

m)

30

35

40

45

50

55

60

CF / TCF / CB

vdw + HB + π-π vdw only

Single-Chain Conformations of Conducting Conjugated Polymers from Solution to the Quenching State: A Multiscale Simulation

(CK Lee, CC Hua, and SA Chen, J Phys Chem B 2009, 113, 15937 ; Macromolecules 2011, 44, 320)

PANI-EB MEH-PPV

Vacuum (V) Chloroform (CF)

Chlorobenzene (CB)

Toluene (T)

Mixed CF and T

Angstrom

5 10 15 20 25 30

Lo

ca

l Ra

tio

(C

F :

T)

/ Bu

lk R

ati

o

0.5

1.0

1.5

2.0

3:12:11:11:21:3

Angstrom

5 10 15 20 25 30

Lo

ca

l Ra

tio

(C

F :

CB

) / B

ulk

Ra

tio

0.5

1.0

1.5

2.0

3:12:11:11:21:3

distance (Angstrom)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

RD

Fs

0

1

2

3

4

5

6

7

8

9

10

11

VCFTCBCF+TCF+CB

3.0 3.5 4.0 4.5 5.00

1

2

3

4

5

6

Mixed CF and T

Mixed CF and CB

Mixed CF and CB

Super-Long Chains and Multi-Chain Aggregates

10% defect 5% defect 0% defect

10% defect 5% defect 0% defect

An Ellipsoid-chain Model for Conjugated Polymer Solutions Snapshots of single chain and aggregate cluster

The predicted scaling laws for mean end-to-end distance (ETE) of MEH-PPV

In toluene solution (T)

In chloroform solution (C)

M/C

CGMC;slope = 0.41 ± 0.03CGLD;slope = 0.41 ± 0.02CGMD;slope = 0.38 ± 0.02

M/T

CGMC;slope = 0.33 ± 0.03CGLD;slope = 0.33 ± 0.02CGMD;slope = 0.32 ± 0.01

M/(C+T)

CGMC;slope = 0.34 ± 0.01CGLD;slope = 0.37 ± 0.02CGMD;slope = 0.46 ± 0.01

C. K. Lee, C. C. Hua, and S. A. Chen, J. Chem. Phys. 136, 084901 (2012).

Experimental: Viscometrics, Light Scatterings, and Flow Turbidity

1 / T

.0028 .0030 .0032 .0034 .0036 .0038 0

M/c

RT

(s)

1e-6

1e-5

1e-4

chloroform, heatingchloroform, annealingtoluene, heatingtoluene, annealing

278288298308T (K)

318338348 328

Time (hr)0 200 400 600 800

p/c

(cP

*ml/

mg

)

0.00

.05

.10

.15

.20

.25

.30

.35

.40

chloroform (40oC)

toluene (40oC)

toluene (25oC)

Constant-temperature aging:

Time dependence

Thermal annealing:

Thermal irreversibility

Viscometric Features of MEH-PPV Solutions

5mg/ml 5mg/ml

Hua, C. C.; Chen, C. L.;  Chang, C. W.; Lee, C. K.; Chen, S. A., J. Rheol. 2005, 49, 641. 

Controlling bulk aggregation state in semiconducting conjugated polymer solution

Photoluminescence Spectra

MEH-PPV/toluene

MEH-PPV/chloroform

wavelength (nm)

wavelength (nm)

inte

nsi

ty (

a.u

.)in

ten

sity

(a.

u.)

g (1

) (τ)

τ(μs)

1 mg/ml MEH-PPV/toluene

τ(μs)

3 mg/ml MEH-PPV/tolueneWithout filtration

3 mg/ml MEH-PPV/chloroformg

(1) (τ

)

τ(μs)

With filtration

Without filtration

Dynamic Light Scattering

C. C. Hua, C. Y. Kuo, S. A. Chen, Appl. Phys. Lett. (2008)

θ = 90 ° θ = 90 °

θ = 90 °

Stabilization of bulk aggregation state in semiconducting polymer solutions

Experimental set-up

0.02 mg/mlShear rate = 1,516 s-1

t (μs)

τ T/c

(cm

2 /g)

0.3 mg/mlShear rate = 1,516 s-1

t (μs) t (μs)

1 mg/mlShear rate = 1,516 s-1

Before shear

t (μs)

τ T/c

(cm

2 /g)

3 mg/mlShear rate = 1,516 s-1

C. C. Hua, C. J. Lin, Y. H. Wen, S. A. Chen, J. Poly. Res. (2011)

Flow turbidity measurement-MEH-PPV/DOP

Dynamic Light ScatteringMEH-PPV/DOP

g (1

) (τ)

τ(μs)

θ = 90 °

R or Rg (nm)50 100 150 200 250 300

Gn(

R)

0.00

0.05

0.10

0.15

0.20

0.25

q (nm-1)0.01

P(q

)

0.1

1.0

0.03 mg/ml0.1 mg/ml0.3 mg/ml1 mg/ml3 mg/ml

Rh (nm)100 101 102 103 104

Rh

Gi( R

h)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Translational + internalTranslationalInternal

Rh (nm)100 101 102 103 104

Rh

Gi( R

h)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Translational + internalTranslationalInternal

h 20h B s h(1) 2

c g 2h B s h

20

0

c

h

20

(1.505 ) ( 6 ) coil( , ) , where

(0.77

( )e

5 ) ( 6 )

( )1 exp (

sph

x 2 )( )

p( )

e

( )

re

N

i ii

N

i ii

P xDc dR

R k T Rg q t R D

R k T R

q tP x

P xDq t

P

c dR

x

q<Rg>

0.5 1.0 1.5 2.0 2.5 3.0 3.5

q(0)

/ q3 k B

T

0.02

0.04

0.06

0.08

0.3 mg/ml1 mg/ml3 mg/ml

1 mg/ml MEH-PPV/toluene

translational internal

1 mg/ml MEH-PPV/chloroform

Dynamic structure factor for MEH-PPV Solutions

q<Rg>

0.5 1.0 1.5 2.0 2.5 3.0 3.5

q(0)

/ q3 k B

T

0.02

0.04

0.06

0.080.1 mg/ml0.3 mg/ml1 mg/ml3 mg/ml

Suppressed Internal Motions of MEH-PPV Aggregates

The range of experimental values for polystyrene/toluene solutions

MEH-PPV/toluene MEH-PPV/chloroform

(0) (1)

0

Initial decay rate: ln ( , )qt

g q tt

Yu H. Wen, Po C. Lin, Chi C. Hua, Show A. Chen, J. Phys. Chem. B 2011, 115, 14369.

Prediction for Gaussian coil

MEH-PPV/tolueneMixed Dynamics (Internal + Diffusive)

0.01

0.001

0.01

0.1

60 oC

30 oC

30 oC_aging 9 hr

30 oC_aging 25 hr

0.0001 0.001 0.01 0.1 1 10 100 1000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

30 degree40 degree60 degree90 degree120 degree

time (sec)0 100 200 300 400 500 600 700

G"

/G'

0.01

0.1

1

1.5 hr3 hr6 hr9 hr17 hr25 hr

0.0001 0.001 0.01 0.1 1 10 100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

30 degree40 degree60 degree90 degree120 degree

0.0001 0.001 0.01 0.1 1 10 100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

30 degree40 degree60 degree90 degree120 degree

Conjugated Polymer Gel in Mixing SolventsDLS/SLS Light Scatterings

50 °C

g1 (τ,

q)

9 mg /ml MEH-PPV solution(Chlorobenzene : Nonane = 5 : 3 )30 °C _aging 6 hr

tq2(s/ μm2)

30 °C _aging 25 hr

Slope = -1Slope = -2

Rheological Features

g1 (τ,

q)

tq2(s/ μm2)tq2(s/ μm2)

q(nm-1)

Rq(c

m-1)

Aging process at 30 °CStrain = 0.1, frequency = 1

MD Simulation

g1 (τ,

q)

Summary

Considerable progress has been made in understanding single-chain/aggregate properties of typical conjugated polymer solutions.

The molecular origins of the “memory effect” dictating the quenching morphologies have been partly unveiled

Much remains to be explored, especially the bulk aggregation properties in solution, as well as the impacts of flow processing and solvent evaporations.