			Home About us Contact

Conjugated Materials (conjugated + material)

Distribution by Scientific Domains

Polymers and Materials Science	66%
Chemistry	33%

Selected Abstracts

From Cyclic Iminophosphoranes to ,-Conjugated Materials,

ANGEWANDTE CHEMIE, Issue 48 2009

Gepaarte Strahler: Die phospheniumvermittelte Kupplung eines anellierten ,4 -1,5 -[1,3,2]Diazaphosphols (oder cyclischen Iminophosphorans) liefert ein pseudo-chinoides Dikation mit ausgedehnter ,-Konjugation (siehe Schema), das im nahen Infrarot (NIR) emittiert. [source]

The Energy of Charge-Transfer States in Electron Donor,Acceptor Blends: Insight into the Energy Losses in Organic Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
Dirk Veldman
Abstract Here, a general experimental method to determine the energy ECT of intermolecular charge-transfer (CT) states in electron donor,acceptor (D,A) blends from ground state absorption and electrochemical measurements is proposed. This CT energy is calibrated against the photon energy of maximum CT luminescence from selected D,A blends to correct for a constant Coulombic term. It is shown that ECT correlates linearly with the open-circuit voltage (Voc) of photovoltaic devices in D,A blends via eVoc,=,ECT,,,0.5,eV. Using the CT energy, it is found that photoinduced electron transfer (PET) from the lowest singlet excited state (S1 with energy Eg) in the blend to the CT state (S1,,,CT) occurs when Eg,,,ECT,>,0.1,eV. Additionally, it is shown that subsequent charge recombination from the CT state to the lowest triplet excited state (ET) of D or A (CT,,,T1) can occur when ECT,,,ET,>,0.1,eV. From these relations, it is concluded that in D,A blends optimized for photovoltaic action: i) the maximum attainable Voc is ultimately set by the optical band gap (eVoc,=,Eg,,,0.6,eV) and ii) the singlet,triplet energy gap should be ,EST,<,0.2,eV to prevent recombination to the triplet state. These favorable conditions have not yet been met in conjugated materials and set the stage for further developments in this area. [source]

Liquid-Crystalline Nanostructures: , -Conjugated Oligothiophene-Based Polycatenar Liquid Crystals: Self-Organization and Photoconductive, Luminescent, and Redox Properties (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009
Mater.
Polycatenar , -conjugated oligothiophenes tethering multiple flexible chains can be used as electro-, photo-, and redox-active materials, as reported by Takashi Kato, Takuma Yasuda, and co-workers on page 411. Various functional liquid-crystalline assemblies including smectic, columnar, and micellar cubic nanostructures can be constructed by polycatenar oligothiophenes. This simple and versatile design strategy would be useful for further development of new functional , -conjugated materials. [source]

Living polymerization of substituted acetylenes

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2005
Martin G. Mayershofer
Abstract For many years, considerable research efforts have been dedicated to ,-conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition-metal-based initiating systems comprise not only simple transition-metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single-component systems such as transition-metal alkylidene complexes. Extensive fine-tuning of the electronic and steric properties of initiator,monomer systems eventually allowed the tailor-made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill-defined group 5 and 6 transition metal halide-based initiators, well-defined transition-metal alkylidene complexes, and rhodium(I)-based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723,5747, 2005 [source]

Toward the synthesis of strongly photoluminescing polyesters by entropically driven ring-opening polymerizations

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2008
Richard T. Williams
Abstract A range of strongly fluorescent polyesters incorporating distyrylarylene moieties have been prepared. The polyesters have the potential to be prepared from the corresponding macrocyclic oligomers (MCOs) by entropically driven ring-opening polymerizations (ED-ROP). This reactive macrocyclic oligomer approach to the polymers has the advantage of allowing the deposition of conjugated materials by solution deposition techniques, such as ink-jet, since the macrocycles after deposition can be converted directly on the substrate, in the absence of any external initiator, into solvent intractable thin polymeric films. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Exciton Migration in Conjugated Dendrimers: A Joint Experimental and Theoretical Study

CHEMPHYSCHEM, Issue 18 2009
Muhammet E. Köse Prof.
Abstract We report a joint experimental and theoretical investigation of exciton diffusion in phenyl-cored thiophene dendrimers. Experimental exciton diffusion lengths of the dendrimers vary between 8 and 17 nm, increasing with the size of the dendrimer. A theoretical methodology is developed to estimate exciton diffusion lengths for conjugated small molecules in a simulated amorphous film. The theoretical approach exploits Fermi's Golden Rule to estimate the energy transfer rates for a large ensemble of bimolecular complexes in random relative orientations. Utilization of Poisson's equation in the evaluation of the Coulomb integral leads to very efficient calculation of excitonic couplings between the donor and the acceptor chromophores. Electronic coupling calculations with delocalized transition densities revealed efficient coupling pathways in the bulk of the material, but do not result in strong couplings between the chromophores which are calculated for more localized transition densities. The molecular structures of dendrimers seem to be playing a significant role in the magnitude of electronic coupling between chromophores. Simulated diffusion lengths correlate well with the experimental data. The chemical structure of the chromophore, the shape of the transition densities and the exciton lifetime are found to be the most important factors in determining the size of the exciton diffusion length in amorphous films of conjugated materials. [source]