Other affiliations: University of California, Berkeley, University of Ulm, University of Freiburg ...read more
Bio: Virgil Percec is an academic researcher from University of Pennsylvania. The author has contributed to research in topic(s): Polymerization & Radical polymerization. The author has an hindex of 101, co-authored 798 publication(s) receiving 42465 citation(s). Previous affiliations of Virgil Percec include University of California, Berkeley & University of Ulm.
05 Oct 2006-Journal of the American Chemical Society
TL;DR: It is reported that polarsolvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2), facilitating an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu( 0) atomic species.
Abstract: Conventional metal-catalyzed organic radical reactions and living radical polymerizations (LRP) performed in nonpolar solvents, including atom-transfer radical polymerization (ATRP), proceed by an inner-sphere electron-transfer mechanism. One catalytic system frequently used in these polymerizations is based on Cu(I)X species and N-containing ligands. Here, it is reported that polar solvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2) species in the presence of a diversity of N-containing ligands. This disproportionation facilitates an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu(0) atomic species, while their deactivation is mediated by the nascent Cu(II)X(2) species. Both steps proceed by a low activation energy outer-sphere single-electron-transfer (SET) mechanism. The resulting SET-LRP process is activated by a catalytic amount of the electron-donor Cu(0), Cu(2)Se, Cu(2)Te, Cu(2)S, or Cu(2)O species, not by Cu(I)X. This process provides, at room temperature and below, an ultrafast synthesis of ultrahigh molecular weight polymers from functional monomers containing electron-withdrawing groups such as acrylates, methacrylates, and vinyl chloride, initiated with alkyl halides, sulfonyl halides, and N-halides.
30 Oct 2009-Chemical Reviews
Abstract: Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.
09 Mar 2011-Chemical Reviews
TL;DR: Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds Brad M. Rosen, Kyle W. Quasdorf, Daniella A. Wilson, Na Zhang, Ana-Maria Resmerita, Neil K. Garg, and Virgil Percec report on cross-coupling strategies for high-performance liquid chromatography of carbon dioxide and nitrogen.
Abstract: Nickel-Catalyzed Cross-Couplings Involving Carbon-Oxygen Bonds Brad M. Rosen, Kyle W. Quasdorf, Daniella A. Wilson, Na Zhang, Ana-Maria Resmerita, Neil K. Garg,* and Virgil Percec* Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
26 Sep 2002-Nature
TL;DR: This work finds that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores π-stacks of donors, acceptors or donor–acceptor complexes exhibiting high charge carrier mobilities.
Abstract: The discovery of electrically conducting organic crystals1 and polymers1,2,3,4 has widened the range of potential optoelectronic materials5,6,7,8,9, provided these exhibit sufficiently high charge carrier mobilities6,7,8,9,10 and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical11, whereas polymers have good processability but low mobilities1,12. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications13,14,15,16,17,18, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores π-stacks of donors, acceptors or donor–acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor–acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive π-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.
01 Nov 1995-Macromolecules
12 Sep 2001-Chemical Reviews
25 Oct 2001-Chemical Reviews
08 Mar 2002-Chemical Reviews
Author's H-index: 101