Graphene Synthesis & Graphene/Polymer Nanocomposites - CEMS ...

Graphene Synthesis & Graphene/Polymer Nanocomposites
Ken-Hsuan (Kirby) Liao
Advisors: Dr. Chris Macosko
Dr. Andre Mkhoyan
Department of Chemical Engineering & Materials Science
University of Minnesota
Ph.D. Defense
Minneapolis MN
September 19th, 2012
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• University of Minnesota
- Ph.D. Materials Science, 2008~Present
Graphene Synthesis & Graphene/Polymer Nanocomposites
• Double Bond Chemical Co
- Research & Development Engineering, 2008
Polymeric Materials
• Taiwan Army, 2007~2008
Biography
• National Taiwan University
- M.S. Polymer Science & Engineering, 2005~2007
MS Thesis: Thermoplastic polyurethane composites for dental materials
- B.S. Chemical Engineering, 2001~2005
BS Thesis: Mechanical & thermal properties of thermoplastic polyurethane
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Graphene: monolayer of carbon
atoms packed in 2D hexagonal
manner
Graphene Properties
Modulus 1 TPa
Strength 130 GPa
Electrical Conductivity 6000 S/cm
Surface Area 2600 m 2 /g
Graphene
0-D: Bucky Ball,
1986
2-D: Graphene,
2004
1-D: Carbon
Nanotube, 1991
3-D: Graphite,
1500
3

Why Graphene/Polymer Nanocomposites?
Light-weight stiff materials
Boeing 787, contains 70,000 lb
composites.
From Boeing
Food packaging
From Brown Machine LLC
BMW i8, a car made with
composites.
Conductive coating
Picture From Mission Impossible 4
From Thermal Spray Technology Inc
4

Challenge of Graphene/Polymer Nanocomposites: Dispersion
aspect
ratio
Bicerano, Polymer, 2002, 43, 369
material
needed
>>

Motivation of Novel Graphene Synthesis
Criteria of Graphene Synthesis Process for Nanocomposites:
1. Massive production
2. Low cost
3. Environmental friendly process
4. Easy to transport
6

Graphene Precursor: Graphite Oxide
• Hydrophilic (Carbon/Oxygen=2/1)
• Electrical insulator
GO/water
hydrophilic
Graphene/water
hydrophobic
Gao, W. et al, Nature Nanotechnology 2011, 6, 496
7

Scotch tape surfactant
Novoselov et al,
Science 2004, 306, 666
Approaches to Produce Graphene
Lotya et al,
JACS 2009 131, 3611
Graphite Scotch Tape Nobel Prize
• Advantages:
Pristine graphene
• Disadvantages:
Low Production
Oxidation
H2SO4
KMnO4
2000 o C/s
Schniepp et al,
J. Phys. Chem. B 2006, 110, 8535
• Advantages:
High Production
• Disadvantages:
Slow process
Low bulk density
Hard to transport
Safety issue
4 weeks
cleaning up
hydrazine
Li et al, Nature Nanotechnology
2008, 3, 101
• Advantages:
High Production
Higher bulk density
• Disadvantages:
Hazard chemicals
Slow process 8

Process & Mechanism of Aqueous Graphene
0.34 nm
0.95 nm
Liao, K.-H. et al, ACS Nano, 2011, 5, 1253-1258
XRD:
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Process & Mechanism of Aqueous Graphene
0.34 nm
0.95 nm
1. Liao, K.-H. et al, ACS Nano, 2011, 5, 1253-1258
2. Liao, K.-H. et al, ACS Applied Materials & Interfaces, 2011, 3, 2607-2615
AFM topography:
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Process & Mechanism of Aqueous Graphene
Liao, K.-H. et al, ACS Nano, 2011, 5, 1253-1258
ARG Surface Area:
~400m 2 /g by BET
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Elemental Composition of Aqueous Graphene (ARG)
XPS:
ARG
C/O=2/1
GO/water
hydrophilic
C/O=7/1
ARG/water
hydrophobic
1. Liao, K.-H. et al, ACS Nano, 2011, 5, 1253-1258
2. Liao, K.-H. et al, ACS Applied Materials & Interfaces, 2011, 3, 2607-2615
FTIR:
TEM: HR-TEM:
Dispersion in water:
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Electrical Conductivity of Aqueous Graphene
Graphene Paper
• Advantages:
High production
High bulk density
• Disadvantages:
Slow process
Hazard chemicals
Liao, K.-H. et al, ACS Nano, 2011, 5, 1253-1258
C/O Electrical
Conductivity(S/cm)
GO Film 2/1 ~10 -5
GS Film 7/1 ~10 1
Single-layer graphene yield: 65%
Single + double layer yield: > 90%
Chemically Reduced Graphene: Aqueous Reduced Graphene:
• Advantages:
High production
High bulk density
Fast process
No hazard chemicals involved
13

Dispersion of ARG in TPU
Single solvent blending process: Co-solvent blending process:
Percolation concentration 1.75 wt% Percolation concentration 0.5 wt%
Modulus improved by ~300% (3.0 wt%) Modulus improved by ~650% (3.0 wt%)
Resistance Modulus
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Graphene/Poly-Urethane-Acrylate (PUA) Nanocomposite
Idea: Disperse graphene in flowable oligomer instead of polymer for better dispersion
Graphene: Vorbeck’s thermally reduced graphene (TRG)
Liao, K.-H. et al, Polymer, 2012, 53, 3756
ano2
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Electrical Percolation & Aspect Ratio
Percolation concentration:
0.15 wt%
Af of dispersed TRG:
~750
reported Af of free standing
TRG: 750
Liao, K.-H. et al, Polymer, 2012, 53, 3756
σ c = σ f (φ-φ perc) t
Af : aspect ratio of dispersed filler
σc : conductivity of nanocomposites
σf : conductivity of filler
r : particle radius
t : particle thickness
Φsphere : volume fraction of interpenetrating
spheres (= 0.29)
Φperc : percolation volume concentration
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Mechanical Properties of Graphene/PUA Nanocomposites
Polymerized Graphene/Poly-urethane-acrylate Nanocomposites:
DMA :
Liao, K.-H. et al, Polymer, 2012, 53, 3756
Polymerization heat & Tg by DSC:
Mori-Tanaka model simulated results
(black dash lines) & real modulus (spots):
TRG Load (wt%) H p (J/g) T g (°C)
0 245±16
0.10 244±13
0.25 256±22
0.50 243±15
14±4
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Electrical Percolation Concentration : Literature Summary
Liao, K.-H. et al, Polymer, 2012, 53, 3756
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Motivation: E graphene/E matrix literature summary
0.05 wt% in
PMMA
Brinson et al
Nature Nano 2008
Theoretical
Maximum
Kim, Abdala, Macosko Macromolecules 2010
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Glass Transition Temperature of Graphene/PMMA Nanocomposites
0.05 wt% percolation concentration?
Too low!
30 o C of T g increase?
Too high!
Ramanathan et al, Nat. Nanotech. 2008 3, 327
Control Groups:
As Received PMMA (PMMA)
As Precipitate PMMA (P-PMMA)
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Glass Transition Behavior of Graphene/PMMA Nanocomposites
• Glass transition temperature (Tg ) changed
obviously even without incorporation of graphene!!
• Coagulation process removed surfactant, which
significantly decrease the Tg of PMMA.
The authors did not operate coagulation process
for control groups!!
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T g of Graphene/Polymer Nanocomposites – Physical Blending
Solvent Blending
Matrix
Techn
Polymer ∆Tg (°C) Filler ique Filler Load
PVDF[98] 0 TRG DSC 4 wt%
PBS[138] 0 CRG DMA 2 wt%
LLDPE[139] 0 EG DMA 20 wt%
PVDF[140] 3.5 TRG DMA 0.5 wt%
TPU[122]
PαMSAN/PM
-2 TRG DSC 7 wt%
MA[141] 0 TRG DMA 1 wt%
Rubber[142] 0 GO DSC 10 wt%
TPU[143] -5 EG DSC 10 vol%
TPU[144] 0 TRG DMA 6 wt%
PS[108] 0 CRG DMA 1.94 vol%
PI[107] 2.6 γ-ABA-GO DMA 0.4 wt%
PVA[132] -4.5
1 wt%
PMMA[132] 0.3 0.2 wt%
PEI[132] 0 TRG DSC 0.1 wt%
TPU[145] 0 TRG DMA 4.4 wt%
Melt Blending
PE[146] 0 CRG DMA 2 wt%
PA12[147] 0 CRG DSC 2 wt%
PET[148] < 2 TRG DMA 7 wt%
PTT[149] 0 TRG DSC 7 wt%
PC[111] 0 GO DMA 3 wt%
PP[110] 0 GO DMA 5 wt%
Solvent-Blending: Melt-Blending:
GO: Graphene oxide
CRG: chemically reduced graphene
TRG: thermally reduced graphene
EG: Expanded graphite 22

T g of Graphene/Polymer Nanocomposites – Chemical Blending
In situ Polymerize monomer in the presence of dispersed graphene
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T g of Graphene/Polymer Nanocomposites – Chemical Blending
In situ Polymerization
Matrix Polymer ∆Tg (°C) Filler Technique Filler load
PBI[133] 1.8 Pristine graphene DMA 0.2 wt%
NIPAA[134] 0 Pristine graphene DSC 0.13 wt%
Epoxy[152] 7 TRG DSC 0.05 wt%
PMMA[77] 20 CRG DMA 4 wt%
PMMA[128] 9 CRG DMA 1 wt%
3 GO
PMMA[129]
8 CRG
DMA 1 wt%
14
DSC
19 GO
DMA
PMMA[76]
7 AIBN-GO DSC & DMA
6 wt%
Vinyl Ester[155] 7 TRG -- 0.2 phr
4 GO
0.5 wt%
PUA[156]
3.4 Isocyanate-GO DSC
1 wt%
PUA[157] 0 TRG DSC & DMA 0.5 wt%
PUA[158] 7 CRG DMA 1 wt%
PS[159] 8 PS-modified CRG DSC 2.5 wt%
Commonly T g change was reported for chemical blending process
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T g of Graphene/Polymer Nanocomposites – Aqueous Blending
Aqueous Blending (solvent blending with water as solvent)
Matrix Polymer ∆T g (°C) Filler Technique Filler load
PVA[104] 12 CRG DSC 7.5 wt%
PVA[170] 4 CRG DSC 0.5 wt%
PVA[105] 14 CRG DSC 3.5 wt%
PVA[171] 9 GO DSC 0.72 vol%
PVA[172] 4 GO DSC 0.7 wt%
Chitosan[135] 5 GO DSC 1 wt%
Gelatin[173] 10 GO DSC 2 wt%
PEO[174] 9 TRG DMA 4 wt%
Commonly T g change was
reported for aqueous blending
process
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T g of Nanocomposites & Polymer Nano-confinement
Nanoconfinement & nanocomposites
Tacticity effect of nanoconfinement
Mayes A, Nature Materials 2005, 4, 651
Grohens Y et al. Langmuir 1998, 14, 2929
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Dispersion of TRG/PMMA Nanocomposites
Samples: TRG/syndiotactic-rich-PMMA (a-PMMA)
TRG/isotactic-PMMA (i-PMMA)
in situ TRG/PMMA
Resistance: (by 11-Probe) Modulus:
Dispersion levels of TRG are similar
Af ~200
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Tacticity Effect on T g of TRG/PMMA Nanocomposites
Samples: TRG/a-PMMA
TRG/i-PMMA
tanδ [tan(E”/E’)] by DMA of:
TRG/a-PMMA i-PMMA
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Tacticity Effect on T g of TRG/PMMA Nanocomposites
Interaction Density:
i-PMMA > a-PMMA
Interaction Intensity:
i-PMMA > a-PMMA
n(T): number of H-bonds per P2VP block
Noro, Matsushita, Lodge Macromolecules
2008, 41, 5839-5844
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Process Effect on T g of TRG/PMMA Nanocomposites
Samples: in situ TRG/PMMA
TRG/a-PMMA
tanδ [tan(E”/E’)] by DMA of:
TRG/atactic-PMMA in situ TRG/PMMA
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Possible Reactions during in situ Polymerization
~1 % of PMMA covalently grafted on TRG
31

Process of separating filler and matrix polymer for in situ system
In situ TRG/PMMA
nanocomposites film
dissolve
in THF filtration
rinse
T g by DSC:
dry
32

Process of separating filler and matrix polymer for in situ system
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inding holes perfectly covered by single-layer GO:
TEM:
AFM:
Lee, C. et al Science 2008, 321, 385
Oxygen Effect on Graphene Oxide
TEM grid
Hole size: 2.5µm in diameter
Force = (TM Deflection) × (Cantilever Spring Constant)
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Lee, C. et al Science 2008, 321, 385
Atomic structure of single-layer GO:
Mkhoyan, K. A. et al, Nano Letters, 2011, 9, 1058
Oxygen Effect on Graphene Oxide
Bridge (C-O-C) bonds
were removed after
chemical reduction
TEM grid
Hole size: 2.5µm in diameter
Force = (TM Deflection) × (Cantilever Spring Constant)
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Fast, scalable,
green process with
massive production
Conclusion
In situ Polymerization
Melt Blending
Solvent Blending
• Mechanical Properties: Elastic modulus increase 100% with 0.5 wt% of graphene
• Thermal Properties: Glass transition temperatures affected by process and tacticity
• Electrical Properties: Surface resistance decrease 10 10 times with 1 wt% of graphene
• Techniques used: AFM, Rheometer, DMA, XRD, SAXS, TEM, SEM, XPS, FTIR,
GPC, TGA, DSC, universal tensile testing instrument.
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Acknowledgement
• Dr. Chris Macosko (CEMS)
• Dr. Andre Mkhoyan (CEMS)
• Dr. Greg Haugstad
• Steven Maslo, Jerry Yeh
• Group Members
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