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Bulk State (bulk + state)
Selected AbstractsBiocomplementary interaction behavior in DNA-like and RNA-like polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2009Chih-Chia Cheng Abstract A series of nucleobased polymers and copolymers were synthesized through atom transfer radical polymerization (ATRP). Biocomplementary DNA- and RNA-like supramolecular complexes are formed in dilute DMSO solution through nucleobase recognition. 1H NMR titration studies of these complexes in CDCl3 indicated that thymine-adenine (T-A) and uracil-adenine (U-A) complexes form rapidly on the NMR time scale with high association constants (up to 534 and 671 M,1, respectively) and result in significant Tg increase. WAXD and differential scanning calorimetry analyzes in the bulk state indicate the presence of highly physical cross-linked structures and provide further details into the nature of the self-assembly of these systems. Furthermore, this study is of discussion on the difference in the hydrogen bond strength between T-A and U-A base pairs within polymer systems, indicating that the strength of hydrogen bonds in RNA U-A pairs is stronger than that in DNA T-A base pairs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6388,6395, 2009 [source] Hydrogen bond-mediated self-assembly and supramolecular structures of diblock copolymer mixturesPOLYMER INTERNATIONAL, Issue 5 2009Shiao-Wei Kuo Abstract This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self-assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self-assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry [source] Control of orientation for carbazole group in comb copolymers arranged by method of organized molecular filmsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2007Hiroko Hoshizawa Abstract We investigated the molecular orientation of organized molecular films with regard to solid-state structures for newly synthesized comb copolymers with N -vinylcarbazole (NVCz) by in-plane and out-of plane X-ray diffraction (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). In the bulk state, hydrogenated and fluorinated comb copolymers form side-chain crystals for a two-dimensional lattice spacing of 4.2 and 5.0,Å, respectively. The findings suggest that the carbazole rings in the main-chain are arranged in opposition to each other. From the results of the DSC measurement, sharp-shaped melting peaks appear on the relatively lower temperature side of the thermograms. This result supports the formation of side-chain crystals in the synthesized comb copolymers. These monolayers of the copolymers on the water surface were extremely condensed, except for the fluorocarbon:NVCz,=,1:1 copolymer. From the in-plane XRD measurement of multilayers on solids, the changes in the two-dimensional lattice structure of fluorinated comb copolymer films containing NVCz units, as opposed to their bulk state, were confirmed. It seems that these structural changes are caused by the stronger ,,, interaction between the carbazole rings rather than the van der Waals interaction between fluorocarbons. Copyright © 2007 John Wiley & Sons, Ltd. [source] Reinforced Self-Assembly of Hexa- peri -hexabenzocoronenes by Hydrogen Bonds: From Microscopic Aggregates to Macroscopic Fluorescent OrganogelsCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2008Xi Dou Abstract Hexa- peri -hexabenzocoronene derivatives (HBCs) that have hydrogen-bonding functionalities (either amido or ureido groups) adjacent to the aromatic cores have been synthesized to study the effects of intracolumnar hydrogen bonds on the self-assembly behavior of HBCs. The hydrogen bonds effectively increased the aggregation tendency of these compounds in solution. In the bulk state, the typical columnar supramolecular arrangement of HBCs was either stabilized substantially (1,a, 1,b, 2,a, and 2,b), or suppressed by dominant hydrogen-bonding interactions (3). For some of the compounds (1,a, 2,a, and 2,b), the supramolecular arrangement adopted in the liquid-crystalline state was even retained after annealing, presumably owing to the reinforcement of the ,-stacking interactions by the hydrogen bonds. Additionally, the combined effect of the hydrogen bonds and ,-stacking of the aromatic moieties led to the formation of fluorescent organogels, whereby some derivatives were further investigated as novel low molecular-mass organic gelators (LMOGs). [source] Hydrogen Storage Mediated by Pd and Pt NanoparticlesCHEMPHYSCHEM, Issue 15 2009Miho Yamauchi Dr. Abstract The hydrogen storage properties of metal nanoparticles change with particle size. For example, in a palladium,hydrogen system, the hydrogen solubility and equilibrium pressure for the formation of palladium hydride decrease with a decrease in the particle size, whereas hydrogen solubility in nanoparticles of platinum, in which hydrogen cannot be stored in the bulk state, increases. Systematic studies of hydrogen storage in Pd and Pt nanoparticles have clarified the origins of these nanosize effects. We found a novel hydrogen absorption site in the hetero-interface that forms between the Pd core and Pt shell of the Pd/Pt core/shell-type bimetallic nanoparticles. It is proposed that the potential formed in the hetero-interface stabilizes hydrogen atoms rather than interstitials in the Pd core and Pt shells. These results suggest that metal nanoparticles a few nanometers in size can act as a new type of hydrogen storage medium. Based on knowledge of the nanosize effects, we discuss how hydrogen storage media can be designed for improvement of the conditions of hydrogen storage. [source] | |||||||||||||