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2010
David Eisenberg, Jackson, Edward A, Quimby, Jennifer M, Scott, Lawrence T, and Shenhar, Roy . 2010. The Bicorannulenyl Dianion: A Charged Overcrowded Ethylene. Angewandte Chemie-International Edition, 49, Pp. 7538-7542. doi:10.1002/anie.201002515. Abstract
Super bowl: Bicorannulenyl, a large biaryl composed of two corannulene bowls, effectively becomes an overcrowded ethylene upon reduction to form a dianion (see picture). DFT calculations and NMR spectroscopic experiments reveal the double-bond character of the connection between the two bowls. Three stable diastereomers that interconvert through bowl inversions and central bond rotations were shown to exist.
David Eisenberg, Quimby, Jennifer M, Jackson, Edward A, Scott, Lawrence T, and Shenhar, Roy . 2010. Highly Charged Supramolecular Oligomers Based On The Dimerization Of Corannulene Tetraanion. Chemical Communications, 46, Pp. 9010-9012. doi:10.1039/c0cc03965a. Abstract
The supramolecular dimerization of tetraanionic corannulene is utilized as a self-assembly motif for the construction of highly charged, buckybowl-based supramolecular oligomers. Oligomers of up to 7 units (3900 g mol(-1)) of reduced dicorannulenic monomers are identified and characterized by various NMR techniques, and the reversibility of their assembly is established through the concentration dependence of their molecular weight and the effect of monofunctional chain-stoppers.
Mariela J Pavan and Shenhar, Roy . 2010. Nanoparticle Organisation Into Branched Morphologies Using Thin Films Of Crystalline Polymers As Dynamic Templates. Journal Of Materials Chemistry, 20, Pp. 1247-1252. doi:10.1039/b917365j. Abstract
We present a facile route for the fabrication of hierarchical, hyper-branched nanoparticle superstructures guided by a two-dimensional polymer template. Our approach utilises semi-crystalline poly(ethylene glycol) (PEG) films featuring branched arrays of channels as templates for the patterning of gold nanoparticles of different sizes and surface chemistry. The deposited nanoparticles preferentially adhere to the channel edges, forming nanoparticle chains decorating the contours of the surface topography. This preference is shown to be independent of nanoparticle size and surface chemistry; however, smaller nanoparticles appear to be more sensitive to subtle topographical attributes of the film. Additionally, the ability to induce the dissolution of the crystalline polymer domains during the nanoparticle patterning process leads to a controlled exchange of these domains with fractal nanoparticle arrays. This dynamic templating methodology adds another dimension to the toolbox of existing patterning methodologies.
David Eisenberg, Shenhar, Roy , and Rabinovitz, Mordecai . 2010. Synthetic Approaches To Aromatic Belts: Building Up Strain In Macrocyclic Polyarenes. Chemical Society Reviews, 39, Pp. 2879-2890. doi:10.1039/b904087k. Abstract
This tutorial review discusses synthetic strategies towards aromatic belts, defined here as double-stranded conjugated macrocycles, such as [n]cyclacenes, [n]cyclophenacenes, Schluter belt, and Vogtle belt. Their appeal stems, firstly, from the unique nature of their conjugation, having p orbitals oriented radially rather than perpendicular to the plane of the macrocycle. Secondly, as aromatic belts are model compounds of carbon nanotubes of different chiralities, a synthetic strategy towards the buildup of structural strain in these compounds could finally open a route towards rational chemical synthesis of carbon nanotubes. The elusiveness of these compounds has stimulated fascinating and ingenious synthetic strategies over the last decades. The various strategies are classified here by their approach to the buildup of structural strain, which is the main obstacle in the preparation of these curved polyarenes.
Elina Ploshnik, Salant, Asaf , Banin, Uri , and Shenhar, Roy . 2010. Co-Assembly Of Block Copolymers And Nanorods In Ultrathin Films: Effects Of Copolymer Size And Nanorod Filling Fraction. Physical Chemistry Chemical Physics, 12, Pp. 11885-11893. doi:10.1039/c0cp00277a.
Two-dimensional, hierarchical assemblies of nanorods were obtained by exploiting the structures afforded by block copolymers in ultrathin films. Under the appropriate conditions, the nanorods segregate to the film surface already upon casting the composite film, and organize with the block copolymer through phase separation. In this paper we compare the structures formed by CdSe nanorods of three different lengths and two polystyrene-block-poly(methyl methacrylate) copolymers with different nanorods/copolymer ratios, and study the temporal evolution of the structure in each case. It is found that the initial morphology of the film largely dictates the resulting structure. The combination of short nanorods and/or short copolymers is shown to be more prone to morphological defects, while assembling long nanorods with long copolymers leads to highly organized nanorod morphologies. These phenomena are explained by a combination of kinetic and thermodynamic factors.
Kostas Ch. Daoulas, Cavallo, Anna , Shenhar, Roy , and Mueller, Marcus . 2010. Directed Assembly Of Supramolecular Copolymers In Thin Films: Thermodynamic And Kinetic Advantages. Physical Review Letters, 105, Pp. 108301. doi:10.1103/PhysRevLett.105.108301.
Using computer simulation of a coarse-grained model for supramolecular polymers, we investigate the potential of quasiblock copolymers (QBCPs) assembled on chemically patterned substrates for creating device-oriented nanostructures. QBCPs are comprised of AB diblock copolymers and supramolecular B segments that can reversibly bond to any available B terminus, on either the copolymers or the B oligomers, creating a polydisperse blend of B homopolymers, and AB and ABA copolymers. We demonstrate the defect-free replication of patterns with perpendicularly crossing, A-preferential lines, where the same QBCP can simultaneously replicate patterns differing by up to 50% in their length scales. We demonstrate how the pattern affects the distribution of molecular architectures and the key role of supramolecular associations for replicating patterns with different length scales.
Elina Ploshnik, Salant, Asaf , Banin, Uri , and Shenhar, Roy . 2010. Hierarchical Surface Patterns Of Nanorods Obtained By Co-Assembly With Block Copolymers In Ultrathin Films. Advanced Materials, 22, Pp. 2774-2779. doi:10.1002/adma.201000573.
Co-assembly of cadmium selenide nanorods in block copolymer films gives rise to anisotropic, hierarchical nanorod superstructures at the film surface. Unlike their observed behavior in the bulk composite, the nanorods preferentially orient perpendicular to the direction of the block copolymer domain, and the number of nanorods assembled across the domain is controlled by the ratio between the nanorod length and the domain width.