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Molecular Films (molecular + film)
Selected AbstractsPolarizability, Susceptibility, and Dielectric Constant of Nanometer-Scale Molecular Films: A Microscopic ViewADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Amir Natan Abstract The size-dependence of the polarizability, susceptibility, and dielectric constant of nanometer-scale molecular layers is explored theoretically. First-principles calculations based on density functional theory are compared to phenomenological modeling based on polarizable dipolar arrays for a model system of organized monolayers composed of oligophenyl chains. Size trends for all three quantities are primarily governed by a competition between out-of-plane polarization enhancement and in-plane polarization suppression. Molecular packing density is the single most important factor controlling this competition and it strongly affects the bulk limit of the dielectric constant as well as the rate at which it is approached. Finally, the polarization does not reach its "bulk" limit, as determined from the Clausius,Mossotti model, but the susceptibility and dielectric constant do converge to the correct bulk limit. However, whereas the Clausius,Mossotti model describes the dielectric constant well at low lateral densities, finite size effects of the monomer units cause it to be increasingly inaccurate at high lateral densities. [source] Solid-state structure and formation of organized molecular films of methacrylate copolymers containing fluorinated and hydrogenated side-chainsPOLYMER ENGINEERING & SCIENCE, Issue 4 2007Atsuhiro Fujimori Surface morphology of monolayers related to solid-state structure for methacrylate comb copolymers having fluorocarbon and hydrocarbon side-chains was investigated by X-ray diffraction (XRD), differential scanning calorimetry, and atomic force microscopy (AFM). From the XRD profiles, two kinds of short spacing peaks were confirmed at 5.0 and 4.2 Å, which assigned the sub-cells for both side-chains. Furthermore, two kinds of endothermic peaks, which corresponded to melting peaks of the both side-chain crystals, appeared in the thermograms. From the AFM observation, it was found that there were hydrogenated domains at a few hundred nanometer diameter in their monolayers, whereas corresponding acrylate copolymer monolayers form the phase-separated structure at 10,30 nm order scales. POLYM. ENG. SCI., 47:354,364, 2007. © 2007 Society of Plastics Engineers. [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] | ||||||||||