wei's work presentation
TRANSCRIPT
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Molecular Nanotechnology
Richard Feynman s talk in 1959, entitled There's Plenty of Room at the Bottom .
K Eric Drexlers 1986 book Engines of
Creation: The Coming Era of Nanotechnology .
Top Down Approach IC, MEMS, etc. Bottom Up Approach Molecular Machine, Ribosome, DNA, Cell
Membrane, etc.
An Overview
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Molecular Nanotechnology
The next big thingis really SMALL
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About Complexity
Small Change in the Force Field orthe Boundary Condition of theInteracting Molecules could Resultin Completely Different Results.
Self-assembly of gold-polymer nanorodsresults in a curved structure.Chad Mirkin, Northwestern University
Self-Assembly: Reversibleprocesses in which pre-existing parts or disorderedcomponents of apreexisting system formstructures of patterns.
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Irreducible Complexity
"a single system which is composed of several interacting parts that contribute to the basic function, and where theremoval of any one of the parts causes the system to effectivelycease functioning". (Michael Behe, Molecular Machines: Experimental Support for the Design Inference )
Solution:
Molecular Interaction DataBase
Computer Simulation:Molecular Dynamics Simulation
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Molecular Dynamic Simulation
(a) Molecular Dynamics simulation"snapshot" of a silicate-surfactant-
polystyrene nanocomposite. (b) The
corresponding number density of carbonatoms as a function of distance.
Schematic of the polymer layeredsilicate nanocomposite (PLSN)morphologies: (a) intercalated and (b)exfoliated.
D.B. Zax, D.-K. Yang, R.A. Santos, H. Hegemann, E.P. Giannelis and E.
Manias. J. Chem. Phys., 112 , 2945, (2000).
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Polymer Nanocomposites (PNC)
ApplicationsHeat-resistant materialsLight weight and high strength structuralmaterials
Electrical package, conductive polymers.Barrier PropertiesCorrosion resistant, coating or structureElectro-magnetic field shieldingSelective photo sensitivity, coatings, etc
It is estimated that widespread use of PNCs by carmanufacturers could save over 1.5 billion liters of gasolineannually and reduce CO 2 emissions by nearly 10 billionpounds!
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Polymer Nanocomposies Popular Nano-reinforcements
BuildingBlocks of the NanoAge
Clay
Other Synthetic Materials
POSS
Graphite
Carbon Nanotube,Bukcyball
Cellulose
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Polymer Nanocomposies Surface Modification, Dispersion
Ion exchange for clays
Addition reaction on CNTs (fullerenes)
Acidification, fluorination, etc. in order to attach differentfunctional groups onto nano reinforcement surface to improvedispersion as well as reactivity with the matrix structuremorphology change & tailoring of interface
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Focus : Carbon Nanotube Functionalization
R 1 NHCH 2 C(=O)OH + R 2 CH=O
DMF, 130 o C 120 h
N H 2 C C H
R 1 R 2
+ _ - H 2 O , C O 2
N
R 2
R 1
x
SWNTs S W N T
R 1 = - C H 2 ( C H 2 ) 6 C H 3 , - C H 2 C H 2 O C H 2 C H 2 O C H 2 C H 2 O C H 3
R 2 = H , O C H 3 ,
ROC(=O)N 3 + SWNT
- N 2
160 oCODCB
SWNT [>NC(=O)OR]
R = tert-Butyl, Ethyl, oligoether groups
Azomethine Ylides M. Prato, A. Hirsch et al., 2001
R
N2+BF4
-
R
NH2
RSWNT
xBu4N
+BF4-
CH 3CN
SWNTs, -1 V (CH 3)2CHCH 2CH 2ONO
SWNTs
ODCB / CH 3CN, 2:1
65 oC
R = tert-Butyl, halogen, COOH, NO 2, COOH, CO 2CH3 etc.
Aryl Diazonium Salts, J. Tour et al., 2001
[F] x-SWNTsF2 /H 2
SWNTsheat
SWNTs + RC(=O)OO(=O)CRheat
- CO 2SWNT[R]x-
R = C 11H23, C6H5, CH2CH2COOH
FluorinationJ. L. Margrave et al., 1998
Acyl PeroxidesV.N.Khabashesku et al., 2002
NitrenesA. Hirsch et al., 2001, 2 003
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Polymer Nanocomposies Network Formation
POSS
Carbon Nanotubes
Controlling FactorsProperties of theMatrix
Properties of theNano-reinforcementInterface Properties
of the Nanocomposites
Interaction betweenReinforcement andMatrix during Loading(Thermal, Mechanical,Electronical, etc.)
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Conflicting Property Reports
Conflicts Result from Differences in Matrix Polymer Repeating Unit
Relative Mobility of Nano-reinforcement Compared with Matrix
Degree of Crosslinking
Polymerization Mechanism
Nano-reinforcement
Surface Treatment
Degree of Dispersion
etc.
DeconvolutionSimple Model System
Experimental Condition
Raw Materials Selection
Molecular Dynamics
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the Future
Properties Design
Microscopic Morphology Control
Optimum Interface Design
Mechanosynthesis of Polymer Chains
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MWCNT/Epoxy Nanocomposites
Structure Change
Morphology Change
Increased Mobility
Thermal Mechanical Properties
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Preparation of Nanocomposites
MWCNT (40-60nm,10 m)
A- CNT PGE-CNT EPON-CNT
Bulk Sample
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Mono-epoxy: PGE
PGE-CNT
Di-epoxy: Epon 828
Epon-CNT
A-CNT
Pure-CNT
Auad, M. L. et al, J. J APPL POLYM SCI 66: (6) 1997
MWCNT/Epoxy Nanocomposites
Surface Treatment (Continued)
A B
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Solubility Change After Modification
Solubility change in water
Pure-CNT A-CNT PGE-CNT EPON-CNT
Increasing solubility in THF
Pure-CNT A-CNT PGE-CNT EPON-CNT
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FTIR Spectrum of Treated CNTs
2920,2850 cm-1C-H Stretch
1710 cm-1
Carboxylic group
1250 cm-1Aromatic Ether
760 cm-1Epoxy ring
12 Band
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CNTs/ Epoxy Composites
Solvent Evaporation
A-CNT
PGE-CNT
Epoxy-CN T
0.9wt%
0.7wt%
0.51wt%
Functionalized CNTdispersed in THF
1wt%
Epoxy (EPON 828)
DMAP (initiator)(-4dimethylamino)pyridine
Crosslinking Reaction
Nanocomposites
Williams et al. Macromol.Mat. and Eng. 289, 315, 2004
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10 m
Morphology: SEM
MatrixEPON 828
10 m
A-CNT
10 m
PGE-CNT
10 m
Pure-CNT
1wt% CNT
10 m
Epon-CNT
CNTs agglomerations
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DMA Test @ 1wt% Treated CNTs
40 60
3000
4000
S t o r a g e M o d u l u s ( M P a )
Temperature (oC)
Pure EpoxyA-CNT Epoxy
PGE-CNT EpoxyEPON-CNT Epoxy
140 160 180
0
1000
S t o r a g e M o d u l u s ( M P a )
Temperature (oC)
Pure EpoxyA-CNT EpoxyPGE-CNT EpoxyEPON-CNT Epoxy
40 60 80 100 120 140 160 180 200 220 240
0
50
100
150
200
250
300
350
L o s s M o d u l u s ( M P a )
Temperature (oC)
EpoxyA-CNT compositePGE-CNT compositeEPON-CNT composite
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MD Simulation of SWCNT&EPON Mixture
Amorphous unit cell, orthorhombic, (7,0) swCNTs dispersed in Epon828
600,000 steps (600ps), NVT ensemble (298K), 1.4 g/cc, 14.9V%, 69W%
0 2 4 6 8 10
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Pair Corelation Function (cnt-cnt;o-cnt)
Blue: 50-150 psRed: 500-600 ps
G a b
( r )
r (Angstrom)
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Stress-Strain Curve/Elastic Constants
Pair Distribution Functions
Tg
Diffusive Behavior
IR Spectrum & Radiation Scattering Function (X-Ray, Neutron)
Concentration Profiles
Temperature Profile
Orientation Correlations
What to simulate in MD?
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CONCLUSIONS
Well dispersed nano-fillers would have a confinementeffect for the matrix, which leads to the improvement of Tg.
The mobility of the polymer chain & the mobility of thenano-fillers dominates the properties of nanocomposites.
Different interfacial bonding would lead to variedimprovement for the glass transition temperature.
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Future Work
Exploring the toughening mechanism of CNT polymer nanocomposites, focus on thermal mechanical properties.
Single walled carbon nanotube reinforced shape memory PU.
Building a MD model for thermoset polymers reinforced withrandomly oriented SWCNTs/ modified SWCNTs.
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Thank You
Questions?
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MD ABC
Molecular Dynamics Simulation
Ideal length and time scale Bridging the molecular level with R EAL WORLD MATERIALS
Materials Structure Characterization and Property Prediction
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Molecular Dynamics Simulation
Initiation:
Definition of Simulation Cell {R (N,V,E)}
* Periodical Boundary Condition
* Minimum Image Convention
Energy minimization (non crystalline)
Assignment of initial velocity {v (N,V,E)}
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Force Fields: Non-bond Covalent Bond
Force = Mass*Acceleration
The force on each atom is related to the partial derivative of potential energy over
the position vector of the atom.
We can derive the ensemble of {R} and {v} of the system after minute time step t
Thus, we can numerically decide the trajectory of the system over time.
Molecular Dynamics Simulation
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Equilibrium:
Allow sufficient number of time steps to be calculated so that the system reachequilibrium --- thermal dynamic data (such as Total Energy, Potential Energy, Cv) no
longer change or oscillate around the equilibrium value. )
Molecular Dynamics Simulation
Data Collection: The trajectory average of the structural or thermal dynamic property over
time will be the simulated value.
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D
1 3 8 2
. 7
1 6 3 5
. 8
CNT
-0.00
0.01
0.02
0.03
0.04
A b s o r b a n c e
8 0 6
. 5 1 0 2 4
. 4
1 1 0 3
. 7
1 2 5 9
. 5
1 3 7 9
. 9
1 4 5 7
. 5
1 5 5 3
. 7
1 6 3 5
. 8
1 7 0 9
. 5
2 3 6 0
. 2
2 8 5 6
. 0
2 9 2 4 . 8
3 4 2 9
. 3
PGE-CNT
-0.0
0.1
0.2
0.3
A b s o r b a n c e
8 1 7
. 8
8 7 7
. 2
1 0 3 0
. 1
1 1 1 0
. 4
1 1 8 2
. 9
1 2 5 6
. 6 1 3 7 9 . 9
1 4 5 1
. 8
1 5 6 7
. 9 1 6 3 3
. 0
1 7 0 9
. 5
2 3 6 0
. 2
2 8 5 0
. 3
2 9 2 2
. 0EPON-CNT
0.000
0.005
0.010
0.015
0.020
A b s o r b a n c e
100015002000250030003500
Wavenumbers (cm-1)