END-FUNCTIONALIZED TRIBLOCK END-FUNCTIONALIZED TRIBLOCK COPOLYMERS AS A ROBUST TEMPLATE COPOLYMERS AS A ROBUST TEMPLATE FOR ASSEMBLY OF NANOPARTICLES FOR ASSEMBLY OF NANOPARTICLES Rastko Sknepnek Rastko Sknepnek , , 1 Joshua Anderson, Joshua Anderson, 1 Monica Monica Lamm, Lamm, 2 Joerg Schmalian, Joerg Schmalian, 1 and Alex Travesset and Alex Travesset 1 1 Department of Physics and Astronomy Department of Physics and Astronomy and and 2 Department of Chemical and Biological Department of Chemical and Biological Engineering Engineering Iowa State University and DOE Ames Iowa State University and DOE Ames Laboratory Laboratory APS March Meeting 2008, New Orleans APS March Meeting 2008, New Orleans March 10, 2008 March 10, 2008 1/11
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END-FUNCTIONALIZED TRIBLOCK COPOLYMERS AS A ROBUST TEMPLATE FOR ASSEMBLY OF NANOPARTICLES Rastko Sknepnek, 1 Joshua Anderson, 1 Monica Lamm, 2 Joerg Schmalian,
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END-FUNCTIONALIZED TRIBLOCK END-FUNCTIONALIZED TRIBLOCK COPOLYMERS AS A ROBUST TEMPLATE COPOLYMERS AS A ROBUST TEMPLATE
FOR ASSEMBLY OF NANOPARTICLESFOR ASSEMBLY OF NANOPARTICLES
Rastko SknepnekRastko Sknepnek,,11 Joshua Anderson, Joshua Anderson,11 Monica Lamm, Monica Lamm,22 Joerg Schmalian,Joerg Schmalian,11 and Alex Travesset and Alex Travesset11
11Department of Physics and Astronomy andDepartment of Physics and Astronomy and22Department of Chemical and Biological EngineeringDepartment of Chemical and Biological EngineeringIowa State University and DOE Ames LaboratoryIowa State University and DOE Ames Laboratory
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008 1/11
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
MotivationMotivation
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• Growing need for complex materials with control of structure and properties Growing need for complex materials with control of structure and properties on on nanometer length scalesnanometer length scales..• Need for a Need for a simplesimple, “single-pass”, but , “single-pass”, but robustrobust fabrication technique. fabrication technique.
Our approachOur approach
Nanoparticle self-assembly via end-functionalized block copolymers.Nanoparticle self-assembly via end-functionalized block copolymers.
• Experimental results:Experimental results:• successful functionalizing of Pluronicsuccessful functionalizing of Pluronic®® triblock copolymers triblock copolymers• successful assembly of calcium phosphate nanocomposites successful assembly of calcium phosphate nanocomposites
• Limited theoretical understanding of self-Limited theoretical understanding of self-assembly of nanoparticle/copolymer assembly of nanoparticle/copolymer composites, especially in solution. composites, especially in solution.
Develop an understanding of mechanisms that lead to successful assemblyDevelop an understanding of mechanisms that lead to successful assemblynanocomposite materials.nanocomposite materials.
CH2
CH2
OCH
CH3
CH2 65
100
O OCH2
CH2
100
CH2
CH2
C O N
O
CON
O
HH peptide
peptide
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
ModelModel Simple coarse-grained bead spring model with implicit solvent.Simple coarse-grained bead spring model with implicit solvent.
Fully flexible bead-spring chain.Fully flexible bead-spring chain. Minimal energy cluster of NMinimal energy cluster of Nnpnp Lennard-Jones Lennard-Jones
particles (particles (Sloane, et al. Discrete Computational Geom. 1995Sloane, et al. Discrete Computational Geom. 1995))
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
Simulation detailsSimulation details Molecular dynamics using LAMMPS.Molecular dynamics using LAMMPS.LAMMPS – S. Plimpton, J. Comp. Phys. 117, 1 (1995)
(lammps.sandia.gov)
Explore phase diagram as a function of:Explore phase diagram as a function of:
Each simulated system contains:Each simulated system contains:• p = 600 copolymer chainsp = 600 copolymer chains• n = 40 – 270 nanoparticles of size Nn = 40 – 270 nanoparticles of size Nnpnp=13(1.2R=13(1.2Rgg), 55(2.1R), 55(2.1Rgg), 75(2.5R), 75(2.5Rgg))• all nanoparticles in a given system are monodisperse all nanoparticles in a given system are monodisperse
10%10% 18%18% 23%23%APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
Depending on the relative nanopaticle concentration one observes a large number Depending on the relative nanopaticle concentration one observes a large number of two- and three-dimensional periodic ordered structures .of two- and three-dimensional periodic ordered structures .
Two-dimensional Two-dimensional square square columnarcolumnar order order
dominates phase dominates phase diagram. diagram.
Square columnar Square columnar order yields to 2D order yields to 2D
hexagonal columnarhexagonal columnar and 3D and 3D gyroidgyroid order. order.
Square columnar Square columnar order is fully order is fully
suppressed and suppressed and novel 3D novel 3D layered layered hexagonalhexagonal order order
appears. appears.
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1.2R1.2Rgg
ResultsResults
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
• dominates phase diagram dominates phase diagram for small NP concentration for small NP concentration
(top view)(top view)
• two-dimensional ordertwo-dimensional order• two interpenetrating two interpenetrating “line-lattices” with lattice “line-lattices” with lattice constant 9.5constant 9.5ss..
9.59.5ss
• closely related to the closely related to the problem of close problem of close packing of binary diskspacking of binary disks
size ratio = 0.414214size ratio = 0.414214concentration = 1/2concentration = 1/2
size ratio = 0.349198size ratio = 0.349198concentration = 6/7concentration = 6/7
Geometric interpretationGeometric interpretation
11.511.5ss
• closely related to the closely related to the problem of close problem of close packing of binary diskspacking of binary disks
• two-dimensional ordertwo-dimensional order• micelles form two-micelles form two-dimensional “line-lattice” dimensional “line-lattice” with lattice constant 11.5with lattice constant 11.5ss• nanoparticles fill space in nanoparticles fill space in betweenbetween
• gyroid order confirmed gyroid order confirmed by structure factor by structure factor • order possess Ia3d order possess Ia3d symmetrysymmetry
• three-dimensional orderthree-dimensional order• micelles and nanoparticles micelles and nanoparticles form two interpenetrating form two interpenetrating gyroidsgyroids• fully connected triply fully connected triply periodic structures periodic structures • nanoparticles stabilize nanoparticles stabilize gyroid over a wide parameter gyroid over a wide parameter rangerange
• three-dimensional layered ordered structurethree-dimensional layered ordered structure• spherical micelles form simple hexagonal latticespherical micelles form simple hexagonal lattice• nanoparticles form layers that resemble honeycombnanoparticles form layers that resemble honeycomb• each nanoparticle layer is stacked between two each nanoparticle layer is stacked between two micellar layers and vice verse. micellar layers and vice verse.
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1.2R1.2Rgg
NN/k/k
BBTT
layered layered hexagonal hexagonal
hexagonal hexagonal columnar columnar
micellarmicellarliquidliquid
gyroidgyroid
ResultsResults Cubic (CuCl) and square columnar orderings, NCubic (CuCl) and square columnar orderings, Nnpnp=75 (2.5R=75 (2.5Rgg))
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008
(square columnar, top view)(square columnar, top view)
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• spherical micelles and nanoparticles form spherical micelles and nanoparticles form two simple cubic latticestwo simple cubic lattices• cubic lattices are shifted by (a/2,a/2,a/2) cubic lattices are shifted by (a/2,a/2,a/2) with respect to each other forming a CuCl with respect to each other forming a CuCl structurestructure• low packing fraction low packing fraction non-trivial non-trivial interaction effects interaction effects
2.5R2.5Rggmicellarmicellarliquidliquid
gyroidgyroid
square square columnar columnar
cubic (CuCl)cubic (CuCl)
Summary and ConclusionsSummary and Conclusions
APS March Meeting 2008, New OrleansAPS March Meeting 2008, New Orleans March 10, 2008March 10, 2008 11/11
• Used a simple coarse grained model to study Used a simple coarse grained model to study nanoparticle self-assemblynanoparticle self-assembly mediated by end-functionalized triblock copolymers.mediated by end-functionalized triblock copolymers.• Extensively studied phase diagram of the nanocomposite system as function Extensively studied phase diagram of the nanocomposite system as function of nanoparticle size, concentration and affinity for copolymer functional ends.of nanoparticle size, concentration and affinity for copolymer functional ends.
• Showed that end-functionalized triblock copolymer can provide a simple, but Showed that end-functionalized triblock copolymer can provide a simple, but powerful strategy for assembling nanocomposite materialspowerful strategy for assembling nanocomposite materials
• very rich phase diagram with five distinct two- and three-dimensional very rich phase diagram with five distinct two- and three-dimensional ordered structuresordered structures• each ordered structure has unique and rich propertieseach ordered structure has unique and rich properties• easy to tune between ordered structures by changing, e.g., easy to tune between ordered structures by changing, e.g., nanoparticle concentration nanoparticle concentration
End-functionalized block copolymers are End-functionalized block copolymers are shown to provide an efficient strategy for shown to provide an efficient strategy for assembly of nanocomposite materials. assembly of nanocomposite materials.