Search results for "Light"
showing 10 items of 3575 documents
Solution processable 2-(trityloxy)ethyl and tert-butyl group containing amorphous molecular glasses of pyranylidene derivatives with light-emitting a…
2015
Abstract Small organic molecules with incorporated 4 H -pyran-4-ylidene (pyranylidene) fragment as the π-conjugation system which bonds the electron acceptor fragment (A) with electron donor part (D) in the molecule – also well known as derivatives of 4-(dicyano-methylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran ( DCM ) laser dye-have attracted considerable attention of scientists as potential new generation materials for organic photonics and molecular electronics due to their low-cost fabrication possibility, flexibility and low-weight. Six glassy derivatives of 4 H -pyran-4-ylidene (pyranylidene) with attached bulky 2-(trityloxy)ethyl and tert -butyl groups are described in this re…
Conductivity and light-induced absorption in BaTiO3
1990
A charge transport model including deep and shallow traps explains both the nonlinear relation between photoconductivity and light intensity and the light-induced absorption in BaTiO3. A correlation between measurements of photoconductivity and light-induced absorption as a function of temperature yields parameters for the shallow center, among them thermal activation energy and generation rate.
Pigment ligation to proteins of the photosynthetic apparatus in higher plants
1997
Ligation of pigments to proteins of the thylakoid membrane is a central step in the assembly of the photosynthetic apparatus in higher plants. Because of the potentially damaging photooxidative activity of chlorophylls, it is likely that between their biosynthesis and final assembly, chlorophylls will always be bound to protein complexes in which photooxidation is prevented by quenchers such as carotenoids. Such complexes may include chlorophyll carriers and/or membrane receptors involved in protein insertion into the membrane. Many if not all pigment-protein complexes of the thylakoid are stabilised towards protease attack by bound pigments. The major light-harvesting chlorophyll a/b prote…
Tetra-alkoxy substituted PPV derivatives: a new class of highly soluble liquid crystalline conjugated polymers
2011
Two first examples of highly soluble tetra-alkoxy substituted PPV derivatives, poly(2,3,5,6-tetrahexyloxy-1,4-phenylene vinylene) (TH-PPV) and poly[2,3,5,6-tetra(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] TEH-PPV, are presented. Both polymers have been fully characterized and the solubility and UV-Vis absorption characteristics have been studied in various organic solvents. Due to the symmetric nature of the repeating unit, TH-PPV and TEH-PPV have an inherently regioregular nature, which is unusual for PPV-type polymers. Observations from polarized light microscopy and differential scanning calorimetry indicate that TH-PPV exhibits thermally induced order resulting in a liquid crystalline m…
Composite soy lecithin–decylpolyglucoside vesicles: A theoretical and experimental study
2008
In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a decylpolyglucoside surfactant, (OrNS10), were formulated and their physicochemical properties were studied with the aim to design a drug delivery system suitable for different applications. To this purpose, morphology, size distribution, ζ-potential and apparent viscosity of the prepared vesicles were studied. Vesicles were also characterized by using optical and light polarized microscopy, transmission electron microscopy and photon correlation spectroscopy. A stability study was …
One-pot synthesis of poly(l-lactide) multi-arm star copolymers based on a polyester polyol macroinitiator
2013
Abstract Using a hyperbranched poly(glycolide) ( hb PGA) macroinitiator the synthesis of poly( l -lactide) (PLLA) multi-arm star polyesters has been achieved via a core-first approach. The star-shaped copolymers were prepared in a one-pot two-step process via Sn(Oct) 2 -catalyzed ring-opening polymerization (ROP) conducted in the melt. Complete conversion of the end groups of the hb polyglycolide polyester polyols is ensured by the reactive primary hydroxyl termini. By adjusting the monomer/initiator ratio a series of star copolymers with varying PLLA arm length has been obtained with molecular weights in the range of 1500 to 10,000 g/mol (SEC). The successful coupling of the PLLA arms to t…
Characterization of Micelles of Polyisobutylene-block-poly(methacrylic acid) in Aqueous Medium
2000
Four amphiphilic block copolymers polyisobutylene-block-poly(methacrylic acid) (IBm-MAAn; m = 70−134, n = 52−228) were synthesized and transferred into aqueous medium at pH 10−12. Their structure in solution was characterized by fluorescence correlation spectroscopy (FCS), static and dynamic light scattering (SLS, DLS), analytical ultracentrifuge (AUC), and by transmission electron microscopy (TEM) with freeze-fracturing and staining techniques. DLS data, AUC sedimentation traces, and TEM images indicate at least two different kinds of particles. TEM shows spherical micelles; however, especially for polymers with larger hydrophobic blocks, additional particles are observed. FCS shows extrem…
Dilute solution properties of polybutadiene modified by 4-phenyl-1,2,4-triazoline-3,5-dione
1996
The dilute solution properties of 4-phenyl-1,2,4-triazoline-3,5-dione-modified polybutadienes were studied in tetrahydrofuran by static and dynamic light scattering and compared with those from unmodified polybutadiene chains. For the unmodified polymer, the scaling laws were established and the coil interpenetration parameter k f0 was determined in the thermodynamically good solvent tetrahydrofuran ; the chains exhibited common flexible chain behavior. For the modified polybutadiene, the results indicate at infinite dilution a weak extent of intermolecular crosslinking via the urazole groups, coupled with a very high extent of intramolecular ring formation. In order to evaluate the fractio…
Hairy Aramide Rod−Coil Copolymers
2010
We have synthesized monodisperse “hairy rod oligomers” based on oligo(p-benzamide)s carrying alkyl side chains and conjugated them with polydisperse poly(ethylene glycol) (PEG) chains. The well-defined oligomers were synthesized from 4-amino-2-hexyloxybenzoic acid using a commercial peptide synthesizer. The PEG conjugated hairy rod−coil block copolymers self-assemble in polar and nonpolar organic solvents. The self-organization in solution was investigated by dynamic light scattering (DSL) and transmission electron microscopy (TEM) as a function of solvent, equilibration time, and polarity of the substrate. Individual fibers and fiberlike bundles of aggregates could be observed. As all hydr…