Deep‐red light‐emitting phosphorescent dendrimer encapsulated tris‐[2‐benzo[b]thiophen‐2‐yl‐pyridyl] iridium (III) core for light‐emitting device applications

New deep‐red light‐emitting phosphorescent dendrimers with hole‐transporting carbazole dendrons were synthesized by reacting tris(2‐benzo[b]thiophen‐2‐yl‐pyridyl) iridium (III) complex with carbazolyl dendrons by DCC‐catalyzed esterification. The resulting first‐, second‐, and third‐generation dendrimers were found to be highly efficient as solution‐processable emitting materials and for use in host‐free electrophosphorescent light‐emitting diodes. We fabricated a host‐free dendrimer EL device with configuration ITO/PEDOT:PSS (40 nm)/dendrimer (55 nm)/BCP (10 nm)/Alq₃ (40 nm)/LiF (1 nm)/Al (100 nm) and characterized the device performance. The multilayered devices showed luminance of 561 cd/m² at 383.4 mA/cm² (12 V) for 15 , 1302 cd/m² at 321.3 mA/cm² (14 V) for 16 , and 422 cd/m² at 94.4 mA/cm² (18 V) for 17 . The third‐generation dendrimer, 17 (η_ext = 6.12% at 7.5 V), showed the highest external quantum efficiency (EQE) with an increase in the density of the light‐harvesting carbazole dendron. Three dendrimers exhibited considerably pure deep‐red emission with CIE 1931 (Commission International de L'Eclairage) chromaticity coordinates of x = 0.70, y = 0.30. The CIE coordinates remained very stable with the current density. The integration of rigid hole‐transporting dendrons and phosphorescent complexes provides a new route to design highly efficient solution‐processable materials for dendrimer light‐emitting diode (DLED) applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7517–7533, 2008     

Photophysical property of rhodamine-cored poly(amidoamine) dendrimers: Simultaneous effect of spirolactam ring-opening and PET process on sensing trivalent chromium ion

Two novel poly(amidoamine) (PAMAM) dendrimers, comprising rhodamine B unit in the core and 1-phenyl-3-methyl-5-pyrazolone unit at the periphery, have been synthesized and characterized. Both dendrimers displayed high selectivity and sensitivity towards Cr³⁺ ion. As considering the potential of being applied as fluorescent sensors for Cr³⁺ ion, we studied the complexes formed between the dendrimers and Cr³⁺ ion. Different PAMAM dendrimers had different recognition mechanism towards Cr³⁺ ion. For dendrimer G2, the recognition of Cr³⁺ was mainly due to the ring-opening of spirolactam. However, it significantly depended on the simultaneous effect of ring-opening of spirolactam and photoinduced electron transfer (PET) in the case of dendrimer G3.     

Dendronized Hyperbranched Macromolecules: Soft Matter with a Novel Type of Segmental Distribution

Dendronization of a hyperbranched polyester with different generation dendrons leads to pseudo‐dendritic structures. The hyperbranched core is modified by the divergent coupling of protected monomer units to the functional groups. Compared to dendrimers, the synthetic effort is significantly less, but the properties are very close to those of high‐generation dendrimers. The number of functional groups, molar mass, and rheology behavior even in the early generation (G1–G4) pseudo‐dendrimers strongly resembles the behavior of dendrimers in higher generations (G5–G8). Comparison of the segmental and internal structure with perfect dendrimers is performed using SANS, dynamic light scattering and viscosity analysis, microscopy and molecular dynamics simulation. The interpretation of the results reveals unique structural characteristics arising from lower segmental density of the core, which turns into a soft nano‐sphere with a smooth surface even in the first generation.     

Synthesis of polyamidoamine dendrimer (PAMAM/CuS/AA) nanocomposite and its application in the removal of Isma acid fast yellow G Dye

The adsorption of Isma acid fast yellow G dye was studied using polyamidoamine (PAMAM)/Copper sulfide (CuS)/AA nanocomposite containing different amounts of CuS by batch technique. PAMAM dendrimer/CuS/AA nanocomposites were synthesized via gamma irradiation cross‐linking method with the aid of sonication. The nanocomposites were characterized by Fourier‐transform infrared, X‐ray diffraction, transmission electron microscope, energy dispersive spectroscopy X‐ray, thermal gravimetric analysis, ultraviolet‐visible, and fluorescence spectroscopy. The size of the CuS nanoparticles was formed in the range of 12–19 nm. The adsorption capacity of the nanocomposites was evaluated as a function of initial dye concentration, pH, adsorbent dosage, and time. It was verified that the adsorption rate fits a pseudo‐second‐order kinetics for initial Isma acid fast yellow G dye concentrations. Results indicated that the adsorption of Isma acid fast yellow G dye fitted well to the Langmuir model. Our results demonstrate that the PAMAM dendrimer/CuS/AA nanocomposite is very promising for removing organic dyes from wastewater. Copyright © 2015 John Wiley & Sons, Ltd.     

Solid‐Phase Synthesis of a Seventh‐Generation Inverse Poly(amidoamine) Dendrimer: Importance of the Loading Ratio on the Resin

Here, this study overcomes the current barriers to efficient solid‐phase synthesis of high‐generation dendrimers by decreasing the loading ratio on the resin. G7 inverse poly(amidoamine) dendrimer is now prepared, for the first time, through a solid‐phase synthesis using only 50% of the available reactive sites and by choosing a large resin. This preparation takes only 15 d to afford highly pure product in 80% yield with precipitation being the only purification procedure used. The results clearly show the amount of the initial monomer loaded on the resin to be a vital factor for the ability to use solid‐phase synthesis to produce large dendrimers. This finding also sets stage for the applications of solid‐phase synthesis for the preparation of other macromolecules.

     

Blockage of Wnt/β‐Catenin Signaling by Nanoparticles Reduces Survival and Proliferation of CLL Cells In Vitro—Preliminary Study

The Wnt/β‐catenin signaling pathway is shown to play a significant role in the control of the survival, proliferation, and differentiation of hematopoietic cells. Studies have confirmed that aberrant activation of canonical Wnt signaling occurs in various forms of leukemia, and is crucial for chronic lymphocytic leukemia (CLL) pathogenesis. The aim of the study is to evaluate the influence of maltotriose (M3) modified fourth generation poly(propylene imine) dendrimers (PPI‐G4) on Wnt/β‐catenin pathway gene expression in CLL (MEC‐1) cells and to compare these findings with those obtained with fludarabine (FA). Microarray data analysis reveals seven of 19 Wnt/β‐catenin pathway genes whose expression changes significantly during dendrimer and FA treatment: WNT10A, WNT6 , and CDH1 among others. PPI‐G4‐M3 is already known to influence MEC‐1 cell apoptosis and proliferation. The obtained results suggest that the reduction in cell survival under the influence of glycodendrimers and FA may be due to loss of Wnt signaling.     

Copper-free click conjugation of methotrexate to a PAMAM dendrimer platform

The synthesis of a generation 5 (G5) poly(amidoamine) (PAMAM) dendrimer platform having cyclooctyne ligands that were subsequently be used for a copper-free Huisgen 1,3-dipolar cycloaddition (click reaction) with azido modified methotrexate is described. The G5 PAMAM dendrimer was first partially (70%) acetylated and then coupled with 20 cyclooctyne ligands through amide bonds. The remaining primary amine groups on the dendrimer surface were neutralized by acetylation. The platform was then ‘clicked’ with different numbers (5, 10, and 17) of γ-azido functionalized methotrexate. The copper-free click reactions were stoichiometric with excellent yields.     

The influence of lateral and terminal substitution on the structure of a liquid crystal dendrimer in nematic solution: A computer simulation study

The choice of lateral and terminal substitution can have a major influence on the structure of a liquid crystalline supermolecule, which in turn can induce radically different phase behaviour. In this study we use molecular dynamics simulations to investigate the shape of a liquid crystal dendrimer within a liquid crystalline solvent. A coarse-grained (CG) simulation model is employed to represent a third generation dendrimer in which 32 mesogenic groups are bonded to chains at the end of each branch of the dendrimer. In this CG-model the liquid crystal groups can be appended either terminally or laterally. This bonding option is used to generate the structure of four separate systems: (a) a dendrimer with 32 terminal mesogens, (b) a dendrimer with 32 laterally appended mesogens, (c) and (d) dendrimers with 16 lateral and 16 terminal groups represented with laterally bonded sites on one side of the molecule, model (c) or next to terminally bonded sites, model (d). The simulations show that the dendrimer is able to change shape in response to molecular environment and that the molecular shape adopted depends critically on the nature of the lateral/terminal susbstitution.     

Synthesis and photoluminescence study of anthracene based dendrimer and dendron

A new type of polyaromatic dendrimer composed of six anthracene groups was synthesized, which showed a monomeric fluorescence feature with a diminished quantum yield due to intramolecular self-quenching processes in the dendritic framework.