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1.
Inside Back Cover: Supramolecular Assembly of Poly(propyleneimine) Dendrimers Driven By Simple Monovalent Counterions (Chem. Eur. J. 51/2015) 下载免费PDF全文
Seyed Ali Eghtesadi Fadi Haso Marjan Alsadat Kashfipour Dr. Robert Scott Lillard Dr. Tianbo Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18863-18863
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Dr. Partha S. Ghosh Prof. Dr. Andrew D. Hamilton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2361-2365
We report here the noncovalent synthesis of thermosensitive dendrimers. Short oligoguanosine strands were linked to the focal point of a dendron by using “click chemistry”, and quadruplex formation was used to drive the self‐assembly process in the presence of metal ions. The dynamic nature of these noncovalent assemblies can be exploited to create combinatorial libraries of dendrimers as demonstrated by the co‐assembly of two components. These supramolecular dendrimers showed thermoresponsive behavior that can be tuned by varying the templating cations or the number of guanines in the oligonucleotide strand. 相似文献
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Dendrons and dendrimers have well‐defined, discrete structures that can be precisely controlled at the molecular lever. Owing to their unique architectures and multiple functionalities, dendritic molecules have shown intensive self‐assembly behavior and functional performance. In particular, they have been shown to be promising candidates for applications in the assembly of gel‐phase materials. Furthermore, the introduction of suitable functional moieties into the core, the branches, and/or the periphery of the dendritic gelators enables the construction of smart and functional supramolecular gel materials. Over the past decade, a number of dendritic organogelators that are based on poly(amino acid), poly(amide), and poly(aryl ether) dendrons, or together with multiple alkyl chains on the periphery, have been reported. This review describes the important developments in dendritic organogelators, with an emphasis on new strategies for the molecular design of dendritic gelators, understanding of driving forces for gel formation, and their evolution for potential applications in smart soft materials. 相似文献
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Elena N. Govorun Konstantin B. Zeldovich Alexei R. Khokhlov 《Macromolecular theory and simulations》2003,12(9):705-713
A mean‐field model for charged dendrimers has been elaborated and applied to Astramol dendrimers of 5th generation in salt‐free solution. The free energy of a dendrimer molecule was minimized with respect to the dendrimer size and to the profile of counterion distribution. The model of highly stretched freely jointed chain was used to describe the elasticity of long branches, the dissociated groups were assumed to be localized mostly on the periphery of the molecule, and the electrostatic interactions were described in the Poisson‐Boltzmann approximation. It was found that the osmotic pressure of counterions leads to moderate expansion of dendrimer molecules upon charging, and a significant fraction of counterions is localized within the dendrimer molecule under typical experimental conditions.
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Self‐Assembly and Gelation of Poly(aryl ether) Dendrons Containing Hydrazide Units: Factors Controlling the Formation of Helical Structures 下载免费PDF全文
Partha Malakar Prof. Dr. Edamana Prasad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5093-5100
Self‐assembly of AB2 and AB3 type low molecular weight poly(aryl ether) dendrons that contain hydrazide units were used to investigate mechanistic aspects of helical structure formation during self‐assembly. The results suggest that there are three important aspects that control helical structure formation in such systems with acyl hydrazide/hydrazone linkage: i) J‐type aggregation, ii) the hydrogen‐bond donor/acceptor ability of the solvent, and iii) the dielectric constant of the solvent. The monomer units self‐assemble to form dimer structures through hydrogen‐bonding and further assembly of the hydrogen‐bonded dimers leads to macroscopic chirality in the present case. Dimer formation was confirmed by NMR spectroscopy and by mass spectrometry. The self‐assembly in the system was driven by hydrogen‐bonding and π–π stacking interactions. The morphology of the aggregates formed was examined by scanning electron microscopy, and the analysis suggests that aprotic solvent systems facilitate helical fibre formation, whereas introduction of protic solvents results in the formation of flat ribbons. This detailed mechanistic study suggests that the self‐assembly follows a nucleation–elongation model to form helical structures, rather than the isodesmic model. 相似文献
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Wenbo Wu Prof. Gui Yu Prof. Yunqi Liu Prof. Cheng Ye Prof. Jingui Qin Prof. Zhen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):630-641
Herein, through a combination of divergent and convergent approaches, coupled with the utilization of the powerful Sharpless “click chemistry” reaction, two series of high‐generation nonlinear optical (NLO) dendrimers have been conveniently prepared in high purity and satisfactory yields. Perfluoroaromatic rings and isolation chromophores were introduced to further improve their comprehensive performance. Thanks to the effects of Ar? ArF self‐assembly and the isolation chromophores, coupled with perfect 3D spatial isolation from the highly branched structure of the dendrimer, G5‐PFPh‐NS displayed very large NLO efficiency (up to 257 pm V?1), which is, to the best of our knowledge, the new record highest value reported so far for simple azo chromophore moieties. High‐quality wide optical transparency and good stability were also achieved. 相似文献
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Woo‐Sik Jang Tomonori Saito Michael A. Hickner Jodie L. Lutkenhaus 《Macromolecular rapid communications》2010,31(8):745-751
Poly(ethylene glycol) (PEG)‐based films, nanotubes, and nanotube arrays were successfully made using layer‐by‐layer (LbL) assembly ion‐containing PEO derivatives on porous templates and planar substrates. PEG nanotubes are challenging to produce because PEG dissolves into solutions and solvents used during nanotube processing, but our techniques circumvent the issue. Nanotube dimensions were verified using microscopy and the average observed diameter was 155 nm. The PEG‐based structures showed remarkable stability in water, salt water, and sodium hydroxide solution.
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The evaporation driven self‐assembly of novel colloidal silica Janus particles was evaluated by scanning electron microscopy in comparison to unfunctionalized silica particles. The cyclodextrin‐ and azobenzene‐modified compound was obtained utilizing Pickering emulsion approach, in which the particles were immobilized on solidified wax droplets and subsequently functionalized. Silica particles were modified with 3‐aminopropyl trimethoxysilane and afterward reacted with tosyl‐β‐CD or phenylazo(benzoic acid), respectively. Mesoscopic structures of the colloidal dispersions, as dried films from aqueous solution, have been investigated by scanning electron microscopy and dynamic light scattering. Interestingly, it has been observed that the Janus particles show a significantly different evaporation‐induced assembly than the unmodified particles. 相似文献
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Two porphyrin‐cored thiophene dendrimers T(3T)P and T(7T)P have been successfully synthesized and characterized by UV‐vis and fluorescence measurements. The self‐assembly of these two water‐insoluble free base porphyrins to form both intrinsic H‐ and J‐aggregates has been reported for the first time. This intrinsic behavior is in contrast to the use of surfactants, dyes, and metal ions to induce aggregation behavior on most porphyrin systems. This work emphasizes the importance of controlling the size, solvent, and extent of conjugation of polythiophene dendron groups in porphyrin systems. These materials may yet be applied to polythiophene or porphyrin blend system in energy conversion devices with the light‐harvesting properties of the polythiophene dendrons.
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Virgil Percec Prof. Mihai Peterca Dr. Yusuke Tsuda Prof. Brad M. Rosen Satoshi Uchida Prof. Mohammad R. Imam Dr. Goran Ungar Prof. Paul A. Heiney Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):8994-9004
The synthesis, and structural and retrostructural analysis of a library of second‐generation conical dendrons that self‐assemble into spherical supramolecular dendrimers is reported. This library consists of amphiphilic dendrons with n‐alkyl groups containing from 4 to 16 carbon atoms. The dendrons containing 6 to 16 carbon atoms in their n‐alkyl groups self‐assemble into spherical supramolecular dendrimers that self‐organize in a Pm n cubic lattice. The structural and retrostructural analysis of the Pm n lattices generated from the supramolecular dendrimers demonstrated that the volume of the aromatic core of the spherical dendrimers is not dependent on the number of carbon atoms from their alkyl groups. This result facilitated the calculation of the average values of the absolute electron density of the aliphatic and aromatic domains of the spherical supramolecular dendrimers. The relative intensity of the higher order diffraction peaks of the Pm n lattice increases as the volume of the aliphatic part of the sphere mediated by the number of carbon atoms in the n‐alkyl groups decreases. This study demonstrates the maximum increase of the relative intensity of the higher order diffraction peaks of the Pm n lattice generated from non‐hollow supramolecular dendrimers. 相似文献
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Chih‐Yuan Hsu Shih‐Chieh Chang Keh‐Ying Hsu Ying‐Ling Liu 《Macromolecular rapid communications》2013,34(8):689-694
In this paper, self‐assembled polymeric toroids formed by a temperature‐driven process are reported. Rhodamine B (RhB) end‐capped poly(N‐isopropylacrylamide) (PNIPAAm) demonstrating a lower critical solution temperature (LCST) is prepared. In a two‐phase system, the polymer in the aqueous phase could move to the chloroform phase on raising the temperature above its LCST. This temperature‐driven process results in the formation of polymeric toroids in the chloroform phase, and the strategy affords a new pathway to toroidal self‐assembly of polymers. Moreover, the photoluminescent behavior of the RhB end‐capped PNIPAAm species formed by the process is also studied and discussed.
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Weizhong Yuan Jinju Wang Lulin Li Hui Zou Hua Yuan Jie Ren 《Macromolecular rapid communications》2014,35(20):1776-1781
A supramolecular block copolymer is prepared by the molecular recognition of nucleobases between poly(2‐(2‐methoxyethoxy)ethyl methacrylate‐co‐oligo(ethylene glycol) methacrylate)‐SS‐poly(ε‐caprolactone)‐adenine (P(MEO2MA‐co‐OEGMA)‐SS‐PCL‐A) and uracil‐terminated poly(ethylene glycol) (PEG‐U). Because the block copolymer is linked by the combination of covalent (disulfide bond) and noncovalent (A U) bonds, it not only has similar properties to conventional covalently linked block copolymers but also possesses a dynamic and tunable nature. The copolymer can self‐assemble into micelles with a PCL core and P(MEO2MA‐co‐OEGMA)/PEG shell. The size and morphologies of the micelles/aggregates can be adjusted by altering the temperature, pH, salt concentration, or adding dithiothreitol (DTT) to the solution. The controlled release of Nile red is achieved at different environmental conditions.
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Yao‐Rong Zheng Hai‐Bo Yang Prof. Dr. Koushik Ghosh Liang Zhao Dr. Peter J. Stang Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7203-7214
The self‐organization of multicomponent supramolecular systems involving a variety of two‐dimensional (2 D) polygons and three‐dimensional (3 D) cages is presented. Nine self‐organizing systems, SS1 – SS9 , have been studied. Each involves the simultaneous mixing of organoplatinum acceptors and pyridyl donors of varying geometry and their selective self‐assembly into three to four specific 2 D (rectangular, triangular, and rhomboid) and/or 3 D (triangular prism and distorted and nondistorted trigonal bipyramidal) supramolecules. The formation of these discrete structures is characterized using NMR spectroscopy and electrospray ionization mass spectrometry (ESI‐MS). In all cases, the self‐organization process is directed by: 1) the geometric information encoded within the molecular subunits and 2) a thermodynamically driven dynamic self‐correction process. The result is the selective self‐assembly of multiple discrete products from a randomly formed complex. The influence of key experimental variables ‐ temperature and solvent ‐ on the self‐correction process and the fidelity of the resulting self‐organization systems is also described. 相似文献
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Caminade AM Turrin CO Majoral JP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(25):7422-7432
Interactions between two precisely defined three-dimensional architectures (DNA and dendrimers) are described. Highly synergetic effects occur, as illustrated in two cases: dendrimers can be used as three-dimensional linkers for oligonucleotides, affording highly sensitive microarrays (biochips), and positively charged dendrimers strongly interact with DNA, allowing penetration inside cells (genetic transfection). 相似文献
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Fátima García Luis Sánchez Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(10):3138-3146
Triangular‐shaped oligo(phenylene ethynylene) amphiphiles 1 a and 1 b decorated in their periphery with two‐ and four‐branched hydrophilic triethyleneglycol dendron wedges, have been synthesized and their self‐assembling properties in solution and onto surfaces investigated. The steric demand produced by the dendritic substituents induces a face‐to‐face rotated π stacking of the aromatic moieties. Studies on the concentration and temperature dependence confirm this mechanism and provide binding constants of 1.2×105 and 1.7×105 M ?1 in acetonitrile for 1 a and 1 b , respectively. Dynamic and static light scattering measurements complement the study of the self‐assembly in solution and demonstrate the formation of rod‐like supramolecular structures in aqueous solution. The nanofibers formed in solution can be efficiently transferred onto surfaces. Thus, TEM images reveal the presence of strands of various thickness, with the most common being several micrometers long and with diameters of around 70 nm. Some of these nanofibers present folded edges that are indicative of their ribbon‐like nature. Interestingly, compound 1 b can also form thick filaments with a rope‐like appearance, which points to a chiral arrangement of the fibers. AFM images under highly diluted conditions also reveal long fibers with height profiles that fit well with the molecular dimensions calculated for both amphiphiles. Finally, we have demonstrated the intercalation of the hydrophobic dye Disperse Orange 3 within the filaments and its subsequent release upon increasing the temperature. 相似文献
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Zijian Zhang Miao Yang Dr. Xinjun Zhang Lichu Zhang Bo Liu Ping Zheng Wei Wang Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(10):2352-2361
Let's stick together : The gelation ability of a dendritic gelator has been enhanced by its complexation with a polyelectrolyte (see figure). This concept provides a route to construct novel functional or ordered materials by complexation of other low‐molecular‐mass functional species with polyelectrolytes.
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Stefania Pettirossi Dr. Gianfranco Bellachioma Prof. Gianluca Ciancaleoni Dr. Cristiano Zuccaccia Dr. Daniele Zuccaccia Dr. Alceo Macchioni Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(21):5337-5347
Supra‐mega ion pairing : Multicationic organoruthenium dendrimers show a notable tendency to self‐aggregate when the concentration is increased, leading to megamers. This tendency increases with the generation. The self‐aggregation of dendrimers to megamers is coupled with a decrease in the extent of ion pairing, as illustrated.