Materials Literature
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At present, diblock copolymer phase behavior in the long-chain limit is considered to be governed by three factors: the volume fraction of one block, φ; the segregation strength of the diblock, χ N; and the conformational asymmetry parameter, ε. This implies that the phase diagrams for polymers of different chemistry…
We report the first synthesis of a stable complex of peroxynitrite coordinated to a transition-metal ion. Solid tris(tetraethylammonium) pentacyanosuperoxocobaltate(III) reacts with 1 equiv. of gaseous nitrogen monoxide to yield tris(tetraethylammonium) pentacyanoperoxynitritocobaltate(III) (1). This novel complex is…
Thin films of polymer blends are molded into strips for investigating the influence of lateral confinement on phase separation. The strip has a width and thickness of 17 μm and 1.0 μm, respectively, and contains a 50/50 blend of poly(methyl methacrylate) (PMMA) and poly(styrene- ran -acrylonitrile) (SAN). Upon anneali…
A series of novel spironaphthoxazine-containing rhenium(I) tricarbonyl diimine complexes, which show interesting photoluminescence behavior involving intramolecular photosensitization, have been synthesized and their photochromic properties studied.
We report herein two new nonlinear optical (NLO) crystals, [Et4N][Cd(XCN)3], where X = S (1) and Se (2), that are transparent from 220 to 3300 nm, covering the entire near-ultraviolet, the visible, and the near-infrared spectral regions and giving rise to a very wide and continuous optical window, which is useful for…
Unusually large spontaneous and piezoelectric fields in the III-V nitrides have led to the making of an entirely new class of two-dimensional electron gas. Fluctuation from a perfectly periodic binary structure in highly polar semiconductor alloys present the same physical situation as a random distribution of microsc…
DFT schemes based on conventional exchange-correlation (XC) functionals have been employed to determine the dipole moment (μ), polarizability (α), and first (β) and second (γ) hyperpolarizabilities of push−pull π-conjugated systems. In addition to the failures already pointed out for α and γ in a recent study on polya…
Tetrachlorophthalic anhydride (1) was reacted with L-leucine (2) in toluene solution at refluxing temperature in the presence of triethylamine and the resulting imide-acid (4) was obtained in quantitative yield. The compound (4) was converted to the N-(tetrachlorophthaloyl)-L-leucine acid chloride (5) by reaction with…
The procedure of five consecutive recycling steps by injection moulding of postconsumer PET was evaluated on the basis of processing and drying parameters. The equations that govern the increase in sample mass of the polymer while in contact with the atmosphere were obtained on the basis of weight variation measuremen…
The imidization and phenylethynyl end-group reaction behavior of phenylethynyl-terminated imide oligomers (LaRC™ PETI-5) with a number-average molecular weight of 2500 g/mol has been extensively interpreted in terms of the disappearance and appearance of several characteristic absorption peaks. Most characteristic FTI…
The influence of the chemical structures of the polyamides on chlorine resistance was studied by measuring their chlorine uptake rates. They were prepared from isophthaloyl dichloride and aliphatic, cycloaliphatic, or aromatic diamines by the solution or interfacial polycondensation method. This study showed that the…
The presence of low molecular weight lactic acid derivatives in films enhanced the degradability of polylactide in a biotic medium. Two different biotic and abiotic series were investigated. The films used for the first abiotic and biotic series (a-1 and b-1 films) initially contained some lactic acid and lactoyl lact…
Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions, and a full zero-t…
We propose the Landau model for lock-in phase transitions in uniaxially modulated improper ferroelectric incommensurate-commensurate systems of class I. It includes Umklapp terms of third and fourth order and secondary order parameter representing the local polarization. The corresponding phase diagram has the structu…
The alpha-helix is a key structural element in a wide range of peptides and proteins. We report here the design, synthesis, and characterization of a modified peptide in which the helix content can be reversibly photoregulated. The peptide contains two cysteine residues that are cross-linked by an azobenzene derivativ…
Nanocomposites with different concentrations of nanofiller were prepared by adding nanosilica filler to the single-phase polyurethane matrix. A control series was prepared with the same concentrations of micron-size silica. The nanosilica filler was amorphous, giving composites with the polyurethane that were transpar…
The first cumulant Ω( k ) of the dynamic structure factor as a function of the magnitude k of the scattering vector was determined from dynamic light scattering measurements for three poly( n -hexyl isocyanate) (PHIC) samples with weight-average molecular weights equal to 1.04 × 10 5, 3.63 × 10 5, and 7.71 × 10 5 in n…
We report laser-induced phase transitions in CdS nanocrystals under radiation of 7 ns laser pulses with a wavelength of 532 nm. The observed change in size distribution of the nanocrystals, as well as the change of their crystal structure from orthorombic to cubic, are uncovered by high-resolution transmission electro…
The 1.54 μm Er3+ photoluminescence excitation (PLE) and photoluminescence (PL) spectra of erbium-doped silicon-rich silicon oxide (SRSO) are investigated. Between 350 and 820 nm, PLE spectra are broad and featureless, and the PL spectra are independent of the excitation wavelengths. The results indicate that in erbium…
We have investigated the local free volume and its thermal fluctuation in an amorphous polymethylsilsesquioxane (PMSQ) consisting only of T 3 (CH 3 SiO 3/2 ) and T 2 (CH 3 Si(OH)O 2/2 ) units using photoisomerization of azobenzene molecularly dispersed in the PMSQ films as a photoprobe over a wide temperature range (4…