共查询到20条相似文献,搜索用时 31 毫秒
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Jrg Barner Rabie Al‐Hellani A. Dieter Schlüter Jürgen P. Rabe 《Macromolecular rapid communications》2010,31(4):362-367
Single chains of a neutral, dendronized polymer with peripheral azide groups ( PG3A ) are co‐deposited onto molecularly modified graphite substrates with a positively charged dendronized polymer ( PG2 ) as well as with negatively charged plasmid dsDNA. PG3A is also prepared near graphite step‐edges. Single PG3A chains are moved with a scanning force microscope tip, into close contact with either of the two polyelectrolytes, as well as the step‐edge at predetermined positions. Treating these structures in situ with UV light leads to photochemically induced cross‐linking between the PG3A chains carrying azide groups and PG2 , dsDNA, and graphite step‐edges, respectively, which is proven by mechanically challenging the “welding” points by pulling on the molecules with the SFM‐tip.
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Xiaoying Lu Jilin Zhang Changchun Zhang Yanchun Han 《Macromolecular rapid communications》2005,26(8):637-642
Summary: We describe an interesting approach to the fabrication of wettability gradients from hydrophobicity to superhydrophobicity in low‐density polyethylene (LDPE) films by first forming high porosity surfaces and placing the specimens onto linear temperature gradients. While the polymer chosen for the study is non‐polar, its microporous layer provides sufficient superhydrophobicity. Lateral gradient heating of the layer results in partial melting of the polymer and correspondingly decreases porosity thus decreasing hydrophobicity.
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Wei Su Xiao‐hua Luo Hua‐fen Wang Lei Li Jun Feng Xian‐Zheng Zhang Ren‐xi Zhuo 《Macromolecular rapid communications》2011,32(4):390-396
We herein develop a facile catalyst‐free method to prepare hyperbranched hydroxyl‐enriched aliphatic polycarbonate according to SCROP strategy. PEG‐attached multiarm hyperbranched copolymer HEHDO‐star‐mPEG was further designed. It was found that HEHDO‐star‐mPEG can self‐assemble into supramolecular multimolecular micelles in water. HEHDO‐star‐mPEG micelle showed excellent stability with respect to micellar size upon dilution, and displayed good cell‐biocompatibility. An anticancer drug of doxorubicin with hydrogen‐bonding functionality was incorporated into obtained micelles to establish a drug delivery system model. A high drug‐loading content as well as sustained release pattern for HEHDO‐star‐mPEG based delivery system was achieved.
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Yung‐Chung Chen Tzong‐Yuan Juang Shenghong A. Dai Tzong‐Ming Wu Jiang‐Jen Lin Ru‐Jong Jeng 《Macromolecular rapid communications》2008,29(7):587-592
Chromophore‐containing dendritic structures (G1, G2) are utilized to intercalate layered silicates, which results in a large d‐spacing up to 126 Å. An exfoliated morphology is obtained by mixing the dendritic structure intercalated layered silicates with polyimide in N,N‐dimethylacetamide solution. The dendritic structures attached on the clay template would arrange in a non‐centrosymmetric manner. This self‐assembled arrangement brought about the electro‐optical coefficients of 5–6 pm · V−1 for these relatively low chromophore‐containing organic/inorganic nanocomposites without resorting to poling. Excellent temporal stability (100 °C) is also achieved.
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Surong Zhou Haifeng Shi Ying Zhao Shichun Jiang Yonglai Lu Yuanli Cai Dujin Wang Charles C. Han Duanfu Xu 《Macromolecular rapid communications》2005,26(4):226-231
Summary: The microstructure and phase transformation of a highly‐branched polyethyleneimine/octadecanoic acid (PEI(OA)1.0) complex were investigated using a combination of DSC, XRD, optical polarised microscopy and temperature dependent FT‐IR spectroscopy. A mesogen‐free thermotropic liquid crystalline state was observed in a certain temperature region. The strong ionic interaction between COO− (from OA) and NH (from PEI) and the hydrophobic interaction between the alkyl side chains contributes to the formation of a thermotropic liquid crystalline structure.
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The intercalation of aluminosilicate clays proceeds via a critical conformation change. Ion exchange of the poly(oxypropylene)diamine salts allows widening of the clay layers from 12 Å to 20 Å and then a sharp increase to 58 Å. The data indicate a critical conformation change of the intercalated amines, thus providing a new way for manipulating nanomaterials and control of polymer conformations in layered silicate confinement.
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Per B. Zetterlund Hirotomo Yamazoe Bunichiro Yamada 《Macromolecular rapid communications》2003,24(2):197-201
Detection of the adduct radical by ESR spectroscopy and after‐effect ESR measurements of the adduct radical concentrations in the photosensitized polymerization of styrene (St) in the presence of dimers of α‐methylstyrene (MSD) and methyl methacrylate have revealed that the dominant mechanism of adduct radical loss changes from bimolecular termination to fragmentation as the temperature is increased beyond 90 °C for St/MSD.
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Yawei Qin Ning Wang Yong Zhou Yingjuan Huang Hui Niu Jin‐Yong Dong 《Macromolecular rapid communications》2011,32(14):1052-1059
This communication reports a strategy for scale‐up of an in situ polymerization technique for polyolefin‐based nanocomposites preparation, taking layered silicate (clay) and multi‐walled carbon nanotubes (MWCNTs) as examples of nanofillers. The strategy is realized by transforming the nanofillers into granular “nanosupports” for Ziegler‐Natta catalysts. With a catalyst to polymer replication effect on particle morphology, the in situ prepared nanocomposites are of controlled granular particle morphology. With the polymer particle morphology controlled, the in situ polymerization technique becomes suitable for industrial olefin polymerization processes for mass production of polyolefin nanocomposites.
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Mehmet Atilla Tasdelen Mustafa Uygun Yusuf Yagci 《Macromolecular rapid communications》2011,32(1):58-62
Well‐controlled radical polymerization of methyl methacrylate can be achieved by in situ photochemical generation of copper (I) complex from air‐stable copper (II) species without using any reducing agent at room temperature. The living character of this polymerization was confirmed by both the linear tendency of molecular weight evolution with conversion and a chain extension experiment.
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Christoph Tonhauser Daniel Wilms Yasmin Korth Holger Frey Christian Friedrich 《Macromolecular rapid communications》2010,31(24):2127-2132
Are hyperbranched polymers capable of forming entanglements? This is the central issue of this contribution. Hyperbranched polyglycerol (hbPG) samples with different molecular weights (600–106 000 g · mol−1), narrow polydispersities (1.2–1.8) and high degrees of branching (≈0.6) were prepared by anionic ring‐opening polymerization. The viscoelastic properties of these polymers with respect to molecular architecture and molar mass were investigated. At low molecular weights “classical” scaling behavior between zero shear viscosity and molecular weight can be observed, whereas between 3 000 and 10 000 g · mol−1 a plateau‐like area is found. The results indicate entanglement dynamics when exceeding a critical molar mass ( ≈ 20 000 g · mol−1) due to entangled hyperbranched polyglycerols.
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Thomas E. Enright Michael F. Cunningham Barkev Keoshkerian 《Macromolecular rapid communications》2005,26(4):221-225
Summary: Nitroxide‐mediated polymerization of styrene in a continuous tubular reactor has been demonstrated for the first time. The polymerization kinetics in the tubular reactor are similar to those in a batch reactor. The number average molecular weight increases linearly with conversion, and chain extension experiments were successful, indicating that the living nature of the polymerization is maintained in the tubular reactor.
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Suprakas Sinha Ray Kazunobu Yamada Akinobu Ogami Masami Okamoto Kazue Ueda 《Macromolecular rapid communications》2002,23(16):943-947
The preparation, characterization, materials properties, crystallization behavior and biodegradability of a polylactide (PLA)/organically modified layered silicate nanocomposite is described. Wide‐angle X‐ray diffraction and high‐resolution TEM analyses confirmed that intercalated stacked and disordered/exfoliated mica layers coexist in the nanocomposite. The nanocomposite showed improved materials properties and crystallization behavior with a simultaneous improvement in biodegradability as compared to neat PLA.
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Jong‐Man Kim 《Macromolecular rapid communications》2007,28(11):1191-1212
In contrast to the conventional two‐step method, which involves the generation of reactive functional groups followed by incubation in a dye solution (a wet developing process), the “precursor approach” enables the rapid and cost‐effective generation of patterned images in one step, without the need for an additional wet process. By using the “precursor approach”, the fluorescence of precursor molecules in polymer films can be effectively manipulated by: (1) photoinduced removal of transient protecting groups; (2) photoinduced protonation or intramolecular proton transfer; (3) photochromism; (4) photoinduced formation of fluorophores; (5) photoinduced oxidative degradation or molecular orientation.
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David Briers Guy Koeckelberghs Isabel Picard Thierry Verbiest Andr Persoons Celest Samyn 《Macromolecular rapid communications》2003,24(14):841-846
Nonlinear optical vinyl polymers with high glass transition temperature (Tg) were prepared by the functionalization of a fluorinated acrylate‐methyl vinyl isocyanate copolymer. A modified pathway to obtain a thiophene bridged chromophore was worked out. Poled films of the polymers show a fairly high and stable nonlinear optical response, even at elevated temperatures.
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Veronica Marin Elisabeth Holder Michael A. R. Meier Richard Hoogenboom Ulrich S. Schubert 《Macromolecular rapid communications》2004,25(7):793-798
Summary: An amino‐functionalized bipyridine ligand was prepared in order to serve as a bridging unit to an activated low‐molecular‐weight monomethyl ether of poly(ethylene glycol) (PEG). Coordination of a ruthenium(II ) phenantroline precursor onto the formed PEG‐containing bipyridine ligand yielded a metal‐containing polymer which shows interesting properties for solar cell applications.