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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
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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.
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Conjugated Polymer vs. Commercial Polymer Solutions?
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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.
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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).
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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
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Single-Chain Statistics and Solvent Quality
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(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.
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Quenched-Chain Morphology vs. Memory Effect?
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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
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Super-Long Chains and Multi-Chain Aggregates
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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).
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Experimental: Viscometrics, Light Scatterings, and Flow Turbidity
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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.
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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 °
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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 °
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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)
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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)
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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.