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MATERIALS RESEARCH SCIENCE AND ENGINEERING CENTER

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Abstract: Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the non-covalent interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their components. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous modification in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.

 

One may define constitutional dynamic materials, as materials whose components are linked through reversible covalent or non-covalent connections and which may thus undergo constitutional variation, i.e. change in constitution by assembly/deassembly processes in a given set of conditions. Because of their intrinsic ability to exchange, incorporate and rearrange their components, they may in principle select them in response to external stimuli or environmental factors and therefore behave as adaptive materials of either molecular or supramolecular nature.

This talk was given at a local TEDx event, produced independently of the TED Conferences. A professor of physics and the director of the Center for Soft Matter Research at New York University, David Pine is one of the original developers of diffusing-wave spectroscopy, an optical technique that has proven useful to study colloid systems. In this talk, Pine talks about programming nano-particles, so-called "pac-man" and "patchy" particles, to hook up and dance with each other using nano-dimples and "sticky DNA", which Nature magazine has called the "New Bond".

 

David J. Pine is an American physicist who has made contributions in the field of soft matter physics, including studies on colloids, polymers, surfactant systems, and granular materials.

 

A professor of physics and the director of the Center for Soft Matter Research at New York University, Pine is one of the original developers of diffusing-wave spectroscopy, an optical technique that has proven useful to study colloid systems. Pine also has a longstanding interest in colloidal self-assembly and in the development of a broad range of colloids for these purposes, including colloidal templating, colloidal clusters, lock-and-key colloids, and patchy colloids with valence.

MRSEC Distinguished Speaker: Jean-Marie Lehn

OCTOBER 21, 2011

Dense Packings of Platonic and Archimedean Solids

• Lectures, round-table discussions, and hands-on training for non-specialists through Master Classes on the state-of-the art single crystal and powder diffractometers

• Speakers, instructors and students from industrial, academic, and national labs

• Lecture topics including application of X-ray diffraction for pharmaceuticals, two-dimensional and synchrotron XRD, neutron diffraction, X-ray fluorescence, crystal design and reactivity, protein crystal characterization

• 64 registrants

• Presentations archived on X-ray Facility website for dissemination

 

• Sponsors: Department of Chemistry, New York University, NYU MRSEC, Bruker AXS, Bristol-Myers Squibb, Stoe & Cie GmbH, MiTeGen, Oak Ridge National Laboratory, Cambridge Crystallographic Data Centre

2nd Annual NYU-Bruker Diffraction Workshop

The ability to design and assemble three-dimensional structures from colloidal particles is limited by the absence of specific directional bonds. As a result, complex or low-coordination structures, common in atomic and molecular systems, are rare in the colloidal domain. Here we demonstrate a general method for creating the colloidal analogues of atoms with valence: colloidal particles with chemically distinct surface patches that imitate hybridized atomic orbitals, including sp, sp2, sp3, sp3d, sp3d2 and sp3d3. Functionalized with DNA with single-stranded sticky ends, patches on different particles can form highly directional bonds through programmable, specific and reversible DNA hybridization. These features allow the particles to self-assemble into ‘colloidal molecules’ with triangular, tetrahedral and other bonding symmetries, and should also give access to a rich variety of new microstructured colloidal materials; nanoclusters not observed otherwise.

MRSEC investigators (Weck & Pine) in Nature: Colloids with valence and specific directional bonding

Abstract: Coatings made from colloidal suspensions play a central role in a broad range of applications such as zeolite-based separation membranes, templates for photonic materials, printed electronics, and biomedical engineering. Uniform coatings are often desired, but these can be difficult to achieve due to various phenomena such as the well-known coffee-ring effect. We are interested in developing a fundamental understanding of the factors that determine whether a coating is uniform, and in this talk we will discuss our work on two problems concerning this issue.  The first problem involves development of a mathematical model for the drying of a droplet laden with colloidal particles. In contrast to prior work, our model accounts for depthwise gradients in particle concentration, and can thus qualitatively capture the formation of colloidal "skins" that are observed experimentally.  The second problem involves an experimental study of the dip coating of nanoparticle suspensions.  We demonstrate that there is a "sweet spot" in the parameter space of solids concentration and withdrawal speed where monolayer coatings can be achieved.  Analysis of the experimental data suggests that in order to obtain such coatings, the substrate needs to be withdrawn rapidly enough to overcome pinning of the liquid-air meniscus on the particles, but not so rapidly that a continuous liquid film is entrained.

MRSEC Speaker: Satish Kumar, April 23, 2012

 

•Filling space with polyhedra is a problem dating back to at least to the ancient Greeks. Such space-filling structures (also called “tilings”) have an intimate relationship to the spatial arrangement of crystals, quasicrystals, and DNA, and have important applications in communications, cryptography, information theory and in the search for gravitational waves.

 

• It was long believed that tilings associated with the fcc crystal and its close relatives (called the “octet truss” by Buckminster Fuller) were the only tilings composed of regular tetrahedra and octahedra. In this work, we have identified and analyzed a new family of a infinite number of periodic tilings of 3D space with regular tetrahedra and octahedra. The periodic repeat unit of the tilings contains an octahedron contacting six smaller tetrahedra, which makes the tilings distinctly different and combinatorically richer than the fcc tiling.

 

• The repeat units of our tilings resemble molecular clusters with various symmetries.  How these clusters self-assemble determines their fundamental material properties. These new tilings could be used to model complex multi- component molecular and nano-particle systems under high pressure and enable one to design unique building blocks for targeted self-assembly.

 

•J. Conway, Y. Jiao, and MRSEC Investigator, Sal Torquato  PNAS 2011, in press.

New Ways to Fill Space with Tetrahedra and Octahedra

Materials science is part of the fabric of everyday life, impacting society through key technology sectors ranging from health to transportation to energy to computers, yet the underlying principles that define the properties of everyday and advanced materials are typically not addressed in undergraduate science curricula. Together we will develop modules designed to expose students to the science underlying tangible objects they experience daily and feel are relevant to their lives, imprinting important scientific principles in ways other subjects often cannot achieve. Moreover, the interdisciplinary nature of materials science provides a natural mechanism for introducing into undergraduate courses in the physical sciences.

 

Workshop Topics:

Holographic Video Microscopy

Crystals and Light

Packing: From Marbles to Dice

Lithography and Electronic Materials

Polymer Chemistry

 

The Material World Workshop

Dense particle packings have served as useful models of the structures of liquid, glassy and crystalline states of matter, granular media, and biological systems. Probing the symmetries and other mathematical properties of the densest packings is a problem of interest in discrete geometry and number theory. Previous work has focused mainly on spherical particles—very little is known about dense polyhedral packings.

 

We formulate the generation of dense packings of polyhedra as an optimization problem, using an adaptive fundamental cell that is allowed to shrink and change shape. We find the densest known packings of the four non-tiling Platonic solids (tetrahedron, octahedron, dodecahedron and icosahedron) in 3D Euclidean space.

 

Our simulation results, rigorous upper bounds and theoretical arguments leads us to the conjecture that the densest packings of the Platonic and Archimedean solids with c entral symmetry (16 different polyhedra) are given by their corresponding densest lattice packings. This is the analogue of Kepler’s sphere conjecture for these solids.

MRSEC investigators: S. Torquato and Y. Jiao

Nature, 2009, 460, 876

MRSEC Senior Investigator David Pine: TEDx Talk

(Click here for TEDx video)