Materials Literature
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In situ FTIR measurements of functional group ionization are reported for polyelectrolyte multilayer thin films, composed of a weak polycarboxylic acid and one of several polycations each having different charge densities. The stability of the multilayers in salt solutions increased dramatically when the pH of the sol…
The respective affinities of various imidazole derivatives, imidazole (ImH), 2-methylimidazole (2-MeImH), 2-phenylimidazole (2-PhImH), N-methylimidazole (N-MeIm), 2-methylbenzimidazole (2-MeBzImH), and 4,5-dimethylbenzimidazole (4,5-Me(2)BzImH), for two phenanthroline (Phen) strapped zinc(II) porphyrin receptors porph…
We have studied low-frequency resistance fluctuations (noise) in a single crystal of the rare-earth perovskite manganite ${\mathrm{Pr}}_{0.63}{\mathrm{Ca}}_{0.37}{\mathrm{MnO}}_{3},$ which shows a charge-ordering transition at a temperature ${T}_{\mathrm{CO}}\ensuremath{\approx}245\mathrm{K}.$ The measurements were ma…
The electronic conductivity of PbS and CdTe nanoparticle monolayers was examined voltammetrically by using interdigitated array (IDA) electrodes at the air|water interface. Their band gap energies were estimated from the I − V responses and were very consistent with results obtained from optical measurements as well a…
A new series of morphologically stable, glassy chiral-nematic liquid crystals were synthesized following three distinct deterministic approaches. A glass transition temperature from 67 to 82 °C and a clearing temperature from 175 to 225 °C were accomplished. A helical pitch length from 188 to 210 nm emerged with enant…
A new molecular thermodynamic model is developed of the glass transition temperatures ( T g ) of binary polymer−salt complexes by combining configurational entropy theory with Guggenheim's form of the Debye−Hückel theory. The interactions between the polymer chains and the salt as well as those between cations and ani…
Bistabile molekulare Shuttles, in denen sich ein Makrocyclus über eine vergleichsweise große Strecke (1.5 nm) zwischen zwei Positionen hin- und herbewegt, können durch Licht- oder Wärmeenergie angetrieben werden, vorausgesetzt ΔG zwischen den beiden Zuständen ist hinreichend groß (siehe Bild). Im Beispiel führt die de…
Abstract Polyethylene (PE)‐layered vermiculite (VMT) nanocomposites were fabricated via direct melt compounding in a twin‐screw extruder followed by injection molding. Exfoliated PE/VMT nanocomposites were readily prepared via in situ melt mixing of maleic anhydride modified VMT with PE. Maleic anhydride acts as eithe…
The [ME(8)](n)()(-) ions where M = Cr, Mo; E = As, Sb; n = 2, 3 have been prepared from the corresponding E(7)(3)(-) Zintl ions and M(naphthalene)(2) precursors. The complexes and their [A(crypt)](+) salts (A = Na, K) are formed in 20-45% crystalline yields and have been characterized by UV-vis spectroscopy, EPR, cycl…
Fibrous proteins unlike globular proteins, contain repetitive amino acid sequences, giving rise to very regular secondary protein structures. Silk fibroin from a wild silkworm, Samia cynthia ricini, consists of about 100 repeats of alternating polyalanine (poly-Ala) regions of 12-13 residues in length and Gly-rich reg…
The specific heat of typical relaxors, $\mathrm{P}\mathrm{b}({\mathrm{M}\mathrm{g}}_{1/3}{\mathrm{N}\mathrm{b}}_{2/3}){\mathrm{O}}_{3}$ (PMN) and $\mathrm{P}\mathrm{b}({\mathrm{M}\mathrm{g}}_{1/3}{\mathrm{T}\mathrm{a}}_{2/3}){\mathrm{O}}_{3}$ (PMT), was measured by adiabatic and relaxation methods between 2 and 420 K.…
Giant pentane-soluble organo-silicon dendrimers have been synthesized using a triallylphenol brick according to a new divergent construction that uses a hydrosilylation-nucleophilic substitution sequence up to the ninth generation (G(9)). All the reactions were monitored by (1)H, (13)C, and (29)Si NMR until G(9), indi…
Self-organization on three length scales is exhibited by a block copolymer of styrene and an oligothiophene-bearing isoprene in cast films. For example, a phase-separated nanostructure consisting of π-conjugated oligothiophene molecules is self-aligned perpendicular to the substrate, as revealed in a TEM image of a se…
Dynamic control over the nano-, micro, and macroscopic architectures of materials can be achieved by using living fungi templates for the assembly of DNA-functionalized Au nanoparticles into ordered structures (see scheme). After assembly of one type of particle, a second type of particle can be assembled along the gr…
Carbon-substituted MgB2 single crystals, Mg(B_1-xC_x)_2 of 0.3-1.0 mm size were grown for x=0.02-0.15 by a high-pressure technique. The doping dependence of lattice constants studied in a range of x=0.0-0.2 shows a monotonic decrease in a, while the c parameter remains almost invariant. Using X-ray diffraction and Aug…
By considering a metal/polymer/metal structure within a tight-binding one-dimensional model, we have investigated the polaron formation in the presence of an electric field. When a sufficient voltage bias is applied to one of the metal electrodes, an electron is injected into the polymer chain, then a self-trapped pol…
Holographic reflection gratings in polymer-dispersed liquid crystals (H-PDLCs) were formed by thiol−ene photopolymerization. Using UV laser light and a single prism, electrically switchable reflection gratings in blue, green, yellow, and red colors were fabricated. Results indicate that thiol−ene polymers function as…
Skyrmions in thin metallic ferromagnetic films are stable due to competition between the RKKY interaction and uniaxial magnetic anisotropy. We mimic the RKKY interaction by the next-nearest-neighbors ferromagnetic and antiferromagnetic exchange interactions. We demonstrate analytically and numerically dissipative tran…
It is known that the orientations assumed by thermotropic liquid crystals (LCs) in contact with water are sensitive to the types and concentrations of surfactants and/or polymers present in the aqueous phase. This work expands upon these past observations by developing criteria for surfactants that give rise to a part…
The structural, magnetic, and transport properties of a mono-layered manganite <TEX>$La_{0.7}Sr_{1.3}MnO_{4+{\delta}}$</TEX> were investigated using variable temperature neutron powder diffraction as well as magnetization and transport measurements. The compound adopts the tetragonal I4/mmm symmetry and exhibits no ma…