Wetting, Bonding and Interfacial Energy of Nanocrystalline Metal Particles on Crystalline DCH Polymer and Amorphous Carbon Substrates

Experimental results concerning the interaction between a variety of nanocrystalline metals (gold, silver, nickel and chromium) and both crystalline polymer [poly-DCH (1,6-di (N-carbazolyl)-2,4-hexadiene)] and amorphous carbon substrates, are presented and analyzed. Attention is focused on aspects of the interaction that concern interfacial bonding, its correlation with the cohesive energies of the various metals and the energy of the interfaces. Experimental contributions include qualitative estimates of the magnitude of interfacial energies for the crystalline polymer/metal and amorphous carbon/metal interfaces and a direct measurement of the interfacial energies for gold and silver nanocrystals deposited on the amorphous carbon substrate. The sequence of interfacial energy values for the polymer/metal and amorphous carbon/metal systems is also determined. The interfacial energies for both the poly-DCH and amorphous carbon substrates decreases in the order silver, gold, nickel, and chromium, as expected from cohesive energy, melting point and surface energy data for these elements. The crystalline polymer/metal interfaces were examined for the presence of orientation relationships using selected area diffraction and optical diffractometry of high-resolution TEM images. No orientation relationships were found for any of the polymer/metal combinations spanning a large range of metal reactivities. Lack of atomic matching or some as yet unknown surface condition on the polymer may be responsible for this effect.     

Intercalates of α-Sn(HP04)2·H2O with aromatic and heterocyclic bases and some comments on their orientation in the interlayer region

The intercalation of amines into -tin(IV) hydrogen phosphate, -Sn(HP0₄)₂·H₂0, (-SnP) can occur to give mono- or bilayers of the guest molecule. The distribution and orientation of the amines is influenced by geometrical factors, acidity of the guest molecule and moreover, the degree of charge localisation of the guest organic cations. Regarding the monolayer formation, there are two possibilities. The first is that aromatic amines form monolayers with parallel orientation of the amine with respect to the phosphate layer, when the charge is delocalised over the aromatic ring. Monolayer formation with perpendicular orientation occurs when the positive charge is localised in opposite parts of the aromatic ring molecule. Bilayer formation occurs when the positive charge is localised in one part of the molecule and simultaneous interaction with two adjacent layers is not possible.     

Global symmetry breaking in the nonconserved order parameter system during phase ordering

We study global symmetry breaking in the 2D system of scalar nonconserved order parameter following a quench to zero temperature. We show that the instant of time when the symmetry is broken and the final morphology is chosen corresponds to the saturation of the order parameter inside the domains. There are three possible final morphologies: the positive and negative order parameter final morphology, and the state of the coexisting positive and negative order parameter subsystems with a flat interface between them. We find also that each type of the final morphology constitutes about 1/3 of all cases, what agrees with the results obtained recently by Spirin et al. [Phys. Rev. E 65, 016119 (2001)]. Our results are pertinent for the two dimensional systems, but we suspect that there is also a way to apply similar arguments for the three dimensional ones.     

Polymer-assisted complexing controlled orientation growth of ZnO nanorods

The growth of the oriented zinc oxide (ZnO) nanorods on silicon substrates based on a simple novel chemical transformation and thermal hydrolysis by using polyvinyl alcohol (PVA) as self-assembling complex polymer was introduced in this paper. All the polymers were removed after chemical oxidation and only the carbonized grid backbones remained that confines the ZnO nanorod’s diameter and enhance the absorption and diffusion of ZnO at the tips of the nanorods during growth. The ZnO nanorods are investigated by FTIR, XRD and FE-SEM. The results indicated that these nanorods have fine hexagonal wurtzite crystal structure and their diameter varies from 20 to 90 nm and the length up to about 1 μm. A polymer-localized ZnO growth model is proposed, which well explains the growth behavior of ZnO nanorods.This revised version was published online in August 2005 with a corrected issue number.     

Magnetic alignment in nominally non-magnetic hexagonal metal hydrides: NMR

Powders of three hexagonal metal-hydrides or -deuterides are found to align in 4.4–8.3 T magnetic fields used for NMR. The field-alignment is unexpected, since all three systems have very small susceptibilities, as demonstrated by sharp NMR lines. The extent of alignment runs from nearly complete to barely detectable in ZrBe₂(H,D)_x, LuD₃, and YD₃, respectively. The preferred alignment direction in ZrBe₂(H,D)_x is with the crystallites’ c-axis perpendicular to B, while the c-axis and B tend to be parallel in LuD₃ and YD₃. The susceptibilities χ_|| and χ are determined from bulk magnetization measurements in aligned ZrBe₂H_1.4 powder. The alignment must be considered for proper analysis of NMR spectra in these and related materials.     

Spectral study on the molecular orientation of a tetracationic porphyrin dye on the surface of layered silicates

Tetracationic porphyrin dyes TMPyP and ZnPyP were intercalated into hydrophobized layered silicate films of three smectites. The smectites represented the layered silicate specimens of high (Fluorohectorite, Corning; FHT), medium (Kunipia F montmorillonite; KF) and low layer charge (Laponite, Laporte; LAP). The molecular orientations of the dye cations were studied by means of linearly-polarized ultraviolet-visible (UV-VIS) spectroscopy. The spectral analysis and consequent calculations of tilting angles of the transition moments at the wavelengths of Soret band transitions were in the range of 25°-35°. The determined angles indicated molecular orientation of the dye cations being almost parallel to the surface of the silicates. Slightly higher values (above 35°), determined for a FHT film, indicated either a slightly tilted orientation of the dye cations or the change of molecular comformation after the intercalation of the dye. Presented at 5-th International Conference Solid State Surfaces and Interfaces, November 19–24, 2006, Smolenice Castle, Slovakia     

Orientation and Structure of Ionic Liquid Cation at Air/[bmim][BF4] Aqueous Solution Interface

The watermiscible room temperature ionic liquid 1butyl3methylimidazolium tetrafluorob orate （[bmim] [BF4]） is a model system for studying the interactions between ionic liquid and water molecules. In this work the orientational structure of the low concentrated aqueous solution of [bmim] [BF4] at the air/liquid interface was investigated by sum frequency gener ation vibrational spectroscopy. It has been found that at very low concentrations, the butyl chain exhibited a significant gauche defect, indicating a disordered conformation; and the cation ring oriented with a fairly small tilting angle at the surface. When the concentration increased, the cation ring tended to lie flat at the surface, and the gauche defects of the butyl chain decreased due to the intermolecular chainchain interactions and the consequent more ordered interfacial molecular arrangement. Additionally, the antisymmetric stretching mode in the PPP and SPS spectra exhibited a peak shift, showing that there exists more than one kind of orientation or chemical environment for the butyl CH3 group. These results may shed new light on understanding the surface behavior of watermiscible ionic liquids as well as the imidazolium based surfactants.     

Crown‐ether and azobenzene‐containing liquid crystalline polymers: An influence of macromolecular architecture on optical properties and photo‐orientation processes

A series of novel crown ether‐containing photochromic comb‐shaped liquid crystalline polyacrylates with different macromolecular structure of side groups were synthesized and investigated. Phase behavior, optical and photo‐optical properties of thin spin‐coated films of these polymers were studied. A special attention was paid to a comparative study of the photo‐orientation phenomena occurring in the polymer films under a polarized light action. It was shown that complex formation with the potassium ions results in the decrease in degree of the photoinduced order that can be used for the creation of new materials for sensor devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Confined crystallization of PVDF and a PVDF‐TFE copolymer in nanolayered films

Layer‐multiplying coextrusion was used in conjunction with isothermal recrystallization to study the confined crystallization of polyvinylidene fluoride (PVDF) and polyvinylidene fluoride‐tetrafluoroethylene (PVDF‐TFE) using polycarbonate (PC) and polysulfone (PSF) as confining materials. Three layered systems were produced (PC/PVDF, PSF/PVDF, and PC/PVDF‐TFE) with layer thicknesses ranging from 525 to 28 nm. The crystal morphology was affected by both layer thickness and recrystallization temperature. Specifically, increased recrystallization temperature and decreased layer thickness facilitated the formation of high aspect ratio in‐plane crystals in both PVDF based polymers. On the other side of the spectrum, thicker layers and lower recrystallization temperatures produced on‐edge PVDF crystals and isotropic PVDF‐TFE crystals. The morphology was correlated with oxygen permeability, which decreased by almost two orders of magnitude compared with the bulk. A variety of crystal structures were obtained and explained with nucleation and diffusion theory. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Effects of Baking and Annealing Processes on SrBi2Ta2O9 Film by Sol-Gel Method

Ferroelectric SrBi₂Ta₂O₉ film was prepared using the sol-gel technique. The sol-gel precursor resulted in good ferroelectric performance at annealing temperatures as low as 700°C. The baking profiles changed the orientation and the grain size in the film. The finer grain size and the higher switching charge were consistent under the slower baking profile.