Transcript Document 7209322

Directed Assembly of Nanostructures
Directed Assembly addresses the fundamental scientific issues
underlying the design and synthesis of new nanostructured materials,
structures, assemblies, and devices with dramatically improved
capabilities for many industrial and biomedical applications. It focuses on
discovering and developing the means to assemble nanoscale building
blocks with unique properties into functional structures under wellcontrolled, intentionally directed conditions. Directed assembly is the
fundamental gateway to the eventual success of nanotechnology. It is
based upon well-integrated research efforts that combine computational
design with experimentation to discover novel pathways to assemble
functional multiscale nanostructures with junctions and interfaces
between structurally, dimensionally, and compositionally different building
blocks. These efforts are leading to new methodologies for assembling
novel functional materials and devices from nanoscale building blocks
that will lead to novel applications of nanotechnology to spur industry into
the 21st century.
Center for Directed Assembly of Nanostructures
NSF NSEC at Rensselaer Polytechnic Institute in partnership with the
University of Illinois at Urbana-Champaign, Los Alamos National
Laboratory, Industry, and New York State.
MISSION: We will integrate research, education, and
technology dissemination, and serve as a national
resource for fundamental knowledge and applications,
in directed assembly of nanostructures
 Combine computational design with experimentation to discover novel
pathways to assemble functional multiscale nanostructures with junctions
and interfaces between structurally, dimensionally, and compositionally
different nanoscale building blocks
 Excite and educate a diverse cadre of students of all ages from K-12
through postdoctorate in nanoscale science and engineering
 Work hand-in-hand with industry to develop nanotechnology for the
benefit of society
Structure and Properties of Nanoparticle Gels
Figure: Scaled dimensionless elastic moduli (at 1 Hz) as a
function of polymer concentration scaled by its value at the
fluid-gel transition for a 40% volume fraction nanoparticle
suspension and several values of the polymer-to-particle size
ratio, Rg/R. The line indicates the theoretical prediction based
on a cluster diameter of ~ five particle diameters.
The structural and viscoelastic properties of high volume fraction nanoparticle-polymer suspensions have been
systematically studied experimentally in both the equilibrium fluid and nonequilibrium gel states The low
frequency elastic modulus grows rapidly with increasing depletion attraction near the gel boundary, but becomes a
dramatically weaker function of polymer concentration as the gel state is more deeply entered.
A novel microscopic statistical mechanical theory has been developed and shown to be in good agreement with
experiment for both equilibrium collective nanoparticle structure over all length scales and the location of the gel
boundary. The theory predicts a universal type behavior for the gel elastic modulus as a function of attraction
strength (polymer concentration) and spatial range (polymer size) which has been experimentally verified. Based
on the experimentally deduced non-equilibrium cluster size of roughly five nanoparticle diameters (see Figure),
the no-adjustable-parameter calculations are in excellent agreement with the modulus measurements. (A. Shah, Y.
L. Chen, K. S. Schweizer and C. F. Zukoski, J.Chemical Physics 119, 8747, 2003).
Carbon Nanotube Based Gas Sensor Based on MWNT Arrays
Figure 1. Schematic of carbanion formation and subsequent
initiation of polymerization (a) section of SWNT sidewall
showing sec-butyllithium addition to a double bond and (b)
the carbanion attacks the double bond in styrene and
transfers the negative charge to the monomer. Successive
addition of styrene results and a living polymer chain is
formed.
Figure 2. Aligned multiwalled carbon nanotube arrays
(inset image; scale bar is 100 microns) used as electrode
(anode) in a device (schematic shown on the right) that was
used as a breakdown sensor.
Recent collaborative work of P. M. Ajayan and N. Koratkar at RPI. The idea of gas sensing here is based on an
aligned carbon nanotube array electrode. Gases break down at specific voltages, but conventional breakdown
sensors have bulky architectures, since very high voltages are needed for the breakdown of most common gases.
Here, the nanotubes concentrate the electric field at their tiny tips and hence brings down (several fold; for
example, from ~1000 volts for planar metal electrodes to ~100 volts for a nanotube electrode, for a set electrode
separation) the value of the applied voltage needed for breakdown. The use of nanotube electrodes could
ultimately lead to the fabrication of small portable breakdown gas sensing devices (A. Modi, et al., Nature 424,
171-174, 2003).
Working in Partnership with Industry
 Unrestricted gifts received totaling $1 million annually (with $500K used as
annual NSEC match)
 Results are shared with industry partner on a royalty-free, non-exclusive basis
 Funds company-named graduate and postdoctoral fellows and distinguished
lectures in Materials Science and Engineering at Rensselaer Polytechnic Institute
Electrical behavior of polymer nanocomposites
Mechanical behavior of polymer nanocomposites
Eastman
Kodak
Optical/mechanical multifunctional coatings
Nanocomposites for microelectronics
Nanoscale biomaterials
Nanoscale catalysts
Nanostructured intermetallics
Nanoparticle Control of Polymer Supermolecular Morphology
A collaborative effort between L.S. Schadler, R.W. Siegel, Y. Akpalu (RPI) and ABB focuses on using
nanoparticles to control the supermolecular morphology of semicrystalline polymers and their
properties. The figure shows the effect of 20 nm diameter TiO2 nanoparticles dried or coated with N(2-aminoethyl)3-aminopropyl-trimethoxysilane (AEAPS) on low-density polyethylene (LDPE). There
is no change in unit cell dimension, degree of crystallinity, average lamellar thickness, or average
spherulite size. The supermolecular structure, however, is impacted. Neat LDPE and the dried sample
exhibit a well-defined, impinging, banded spherulite structure. The nanoparticles are embedded
between the lamellae. In great contrast, no well-developed banded spherulites are observed in the
AEPS sample, in which nanoparticles segregate to inter-spherulitic regions. This supermolecular
structure is critical in controlling electrical breakdown strength in LDPE.
m
m
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Figure: AFM tapping mode images of the supermolecular structures of (a) neat LDPE (b) LDPE filled with more
compatible dried TiO2 nanoparticles and (c), LDPE filled with non-compatible AEAPS coated TiO2 nanoparticles.
Educating the Scientists and Engineers of Tomorrow
Junior Museum of Troy
The Molecularium
Introducing 5-9 year olds to the wonders
of the molecular scale world, much the
way that they have been learning about the
wonders of the Universe and Solar System.
BOAST at UIUC
Bouchet Outreach and Achievement in Science and Technology
Stimulating academically at-risk children's interest in science, and
serving as a national resource for hands-on science and Internet
lessons.
Undergraduate Research
Collaboration with Colleges
Mount Holyoke
Providing opportunities to undergraduates in nanotechnology and to
develop a pipeline for a diverse set of graduate students.