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Generation Dendrimer (generation + dendrimer)
Selected AbstractsPhotoresponsive nanocarriers based on PAMAM dendrimers with a o -nitrobenzyl shellJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Yan Li Abstract Gn (n = 3, 4, and 5) poly(amidoamine) (PAMAM) dendrimers were synthesized and peripherally modified with photocleavable o -nitrobenzyl (NB) groups by reacting o -nitrobenzaldehyde with the terminal amine groups of PAMAM dendrimers, followed by reducing the imine to amine groups with NaBH4. The NB-modified dendrimers, Gn-NB (n = 3, 4, and 5), were characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy. The results showed that the NB groups were successfully attached on the periphery of the dendrimers with near 100% grafting efficiency. Such a photosensitive NB shell could be cut off on irradiation with 365 nm ultraviolet (UV) light. The encapsulation and release of guest molecules, that is, salicylic acid (SA) and adriamycin (ADR), by Gn-NB were explored. The encapsulation capability of these dendrimers was found to increase as the guest molecular size was decreased and have dependence on the generation of dendrimers as well. For both of SA and ADR, the average encapsulation numbers per dendrimer decreased in the order of G4-NB > G5-NB > G3-NB, indicating that the fourth generation dendrimer was a better container for the guest molecules. The rate of SA release was found to be greater with UV irradiation than that without, suggesting that the NB-shelled PAMMAM dendrimers could function as a molecular container/box with photoresponsive characteristics. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 551,557, 2010 [source] Self-assembly of well-defined amphiphilic polymeric miktoarm stars, dendrons, and dendrimers in water: The effect of architectureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Daria E. Lonsdale Abstract Five polymeric architectures with a systematic increase in architectural complexity were synthesized by "click" reactions from a toolbox of functional linear polymers and small molecule linkers. The amphiphilic architectures ranged from a simple 3-miktoarm star block copolymer to the more complex third generation dendrimer-like block copolymer, consisting of polystyrene (PSTY) and polyacrylic acid (PAA). Micellization of these architectures in water at a pH of 7 under identical ionic strength gave spherical micelles ranging in size from 9 to 30 nm. Subsequent calculations of the PSTY core density, average surface area per PAA arm on the corona-core interface, and the relative stretching of the PAA arms provided insights into the effect of architecture on the self-assembly processes. A particular trend was observed that with increased architectural complexity the hydrodynamic diameter, radius of the core in the dry state and the aggregation number also increased with the exception of the third generation dendrimer. On the basis of these observations, we postulate that thermodynamic factors controlling self-assembly were the entropic penalty of forming PSTY loops in the core counterbalanced by the reduction in repulsive forces through chain stretching. This results in a greater number of aggregating unimers and consequently larger micelle sizes. The junction points within the architecture also play an important role in controlling the self-assembly process. The G3 dendrimer showed results contradictory to the aforementioned trend. We believe that the self-assembly process of this architecture was dominated by the increased attractive forces due to stretching of the PSTY core chains to form a more compact core. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6292,6303, 2009 [source] A general strategy for highly efficient nanoparticle dispersing agents based on hybrid dendritic linear block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2009Robert Vestberg Abstract A modular approach to the synthesis of a library of hybrid dendritic-linear copolymers was developed based on RAFT polymerization from monodisperse dendritic macroRAFT agents. By accurately controlling the molecular weight of the linear block, generation number of the dendrimer and the nature of the dendritic chains ends, the performance of these hybrid block copolymers as dispersing agents was optimized for a range of nanoparticles. For titanium dioxide nanoparticles, dispersion in a poly(methyl methacrylate) matrix was maximized with a second generation dendrimer containing four carboxylic acid end groups, and the quality of dispersion was observed to be superior to commercial dispersing agents for TiO2. This approach also allowed novel hybrid dendritic-linear dispersing agents to be prepared for the dispersion of Au and CdSe nanoparticles based on disulphide and phosphine oxide end groups, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1237,1258, 2009 [source] Organometallic Complexes for Nonlinear Optics, 47 , Synthesis and Cubic Optical Nonlinearity of a Stilbenylethynylruthenium Dendrimer,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9-10 2010Christopher J. Jeffery Abstract The synthesis of the 1st generation dendrimer 1,3,5-{trans -[Ru(C,C-3,5-(trans -[Ru(C,CPh)(dppe)2(C,CC6H4 -4-(E)-CHCH)])2C6H3)(dppe)2(C,CC6H4 -4-(E)-CHCH)]}3C6H3 proceeds by a novel route that features Emmons-Horner-Wadsworth coupling of 1,3,5-C6H3(CH2PO(OEt)2)3 with trans -[Ru(C,CC6H4 -4-CHO)Cl(dppe)2] and 1-I-C6H3 -3,5-(CH2PO(OEt)2)2 with trans -[Ru(C,CPh)(C,CC6H4 -4-CHO)(dppe)2] as key steps. The stilbenylethynylruthenium dendrimer is much more soluble than its ethynylated analog 1,3,5-{trans -[Ru(C,C-3,5-(trans -[Ru(C,CPh)(dppe)2(C,CC6H4 -4-C,C)])2C6H3)(dppe)2(C,CC6H4 -4-C,C)]}3C6H3 and, in contrast to the ethynylated analog, is a two-photon absorber at telecommunications wavelengths. [source] Core Functionality and Scaling Behavior of Lysine DendrimersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2005Bernd Fritzinger Abstract Summary: A scaling exponent to describe the dependence of the hydrodynamic radius as a characteristic length of the molecule on the molecular weight, has been determined for low generation dendrimers with a thiacalixarene core and lysine dendrons. The hydrodynamic radius has been calculated from the diffusion coefficient measured by pulsed-field-gradient NMR spectroscopy. Scaling exponents of 2.0 for the lysine monodendron, 2.3 for a dendrimer with a bifunctional core, and 3.9 for a dendrimer with a tetrafunctional core have been determined. For a given structure of the dendrons, the scaling exponent reflects the functionality of the core of the dendrimers. Hydrodynamic radius of lysine dendrons as a function of molar mass. [source] Characterization of two series of nitrogen-containing dendrimers by natural abundance 15N NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2008Rodolphe Deloncle Abstract Two series of small generation dendrimers built with phosphorus atoms at each branching point and various types of nitrogen atoms at natural abundance of 15N within the branches are characterized by a gradient enhanced GHNMQC (gradient hydrogen,nitrogen multiple quantum coherence) 1H15N NMR technique. The first series contains two types of nitrogen atoms, included in phosphorhydrazone linkages (CHNNMeP(S)), whereas the second series contains four types of nitrogen atoms included in azobenzene linkages (ArNNAr,) in addition to the phosphorhydrazone. The influence of the trans/cis isomerization of the azo bond on the 15N NMR has also been studied. Despite the low solubility of the azobenzene-containing dendrimers, which renders the detection of some signals difficult, 15N NMR appears as a very sensitive tool to detect chemical changes in the dendritic structure. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||