Materials Literature
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We present a series of new 6,6‘-distyryl-3,3‘-bipyridine derivatives synthesized via a Knoevenagel condensation reaction and disubstituted with electron donor and acceptor groups. These molecules were characterized by spectroscopic methods (NMR, Raman, UV−vis, photoluminescence). These compounds were all found to exhi…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorDendrimers with Both Hydrophilic and Hydrophobic Chains at Every EndYijun Pan and Warren T. FordView Author Information Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078 Cite this: Macromolecules 1999, 32, 1…
A promising route to new functionalized compounds could be provided by two new heteropolyoxothio anions resulting from self−condensation of the [Mo2S2O2]2+ building unit with arsenate or phosphate ions. There is 31P NMR evidence (illustrated) that the three peripheral PO4 or AsO4 groups in the products are labile.
The microphase separation of symmetric cyclic diblock copolymer with decreasing temperature is simulated using the Monte Carlo method. In order to investigate the effect of the ring-shape chain architecture on order–disorder transition (ODT), the microphase separation of the cyclic diblock copolymer is compared with t…
The preparation, rheological behavior, and solution properties of branched poly(3-hydroxy butyrate)- co -(3-hydroxy valerate), PHBV, are described. Branching is produced by the use of dicumyl peroxide (DCP) during the reactive extrusion of PHBV. The shear viscosities of reactively extruded PHBV and the straight-chain…
We report on the structure and dynamics of model mono-, di-, and tri-ω-functionalized three-arm star polybutadiene melts. By using x-ray scattering and dynamic rheological measurements, we find that functionalization of the arm ends can lead to distinctly different supramolecular structures and material behavior. The…
We study the nematic–isotropic transition in model colloidal systems composed of platelets of various shapes using grand canonical simulations. This is of relevance for recently synthesized hard platelet systems, since the platelets in such systems are found to be not circular but irregular hexagons, and so cannot be…
The nanoenvironment provided by the neighboring dendra characteristically influences the redox potentials and the photophysical properties of the tetraphenylporphyrin–zinc (Zn-TPP; denoted as P in Figure) chromophore within the dendrimers 1, which are based on C60 as a structure-determining core. Such functional dendr…
Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was utilized to study simple poly(ethylene glycol)s (PEG) and a series of amphiphilic copolymers prepared from PEG and dendritic molecules. For the amphiphilic copolymers with branched dendritic structures, MALDI-TOF spectrometry…
Despite the relevance to most aspects of crystallization, a comprehensive understanding of the kinetics of heterogeneous nucleation has not been well established yet. In this paper, a new kinetic model based on the “steady-state” approach will be put forward to describe both heterogeneous and homogeneous nucleation. A…
A method, using a Corbino disk sample geometry, is described and applied to study of resistive tails of sintered $YBCO$. When the transport current passes radially from the rim of the disk sample to its center, the two component potential drop signal is detected below $T_c$, which is due to (i) quasiparticles $W_q$ an…
We measured the temperature dependence of the linear high field Hall resistivity of La_0.67Ca_0.33MnO_3 (T_C=232K) and La_0.67Sr_0.33MnO_3 (T_C=345K) thin films in the temperature range from 4K up to 360K in magnetic fields up to 20T. At low temperatures we find a charge carrier density of 1.3 and 1.4 holes per unit c…
Orange− or yellow−orange-colored aqueous dispersions of ultrafine gold particles (∼2 nm) result from the γ-irradiation of deaerated solutions containing hydrolyzed AuCl 4 - and poly(vinyl alcohol) or poly(vinylpyrrolidone), respectively. The particles have a weak and very broad plasmon absorption band with maximum in…
The solvent-free condensation of pyrrole and pentafluorobenzaldehyde (and to a lesser extent other electron-poor aldehydes as well) leads to a variety of products, of which three have been isolated and fully characterized. The two main products (11% each) are an open-chain pentapyrrole and corrole, a tetrapyrrolic mac…
A homologous series of cellulose oligomers from two to eight repeating subunits have been isolated and size-fractionated from the hydrolysis products of microcrystalline cellulose. Chemical modification of cellotriose ( 1 ), cellotetraose ( 2 ), cellopentaose ( 3 ), and cellohexaose ( 4 ) to the corresponding β-methyl…
We conclude from 23Na and 51V NMR measurements in NaxV2O5(x=0.996) a charge ordering transition starting at T=37 K and preceding the lattice distortion and the formation of a spin gap Delta=106 K at Tc=34.7 K. Above Tc, only a single Na site is observed in agreement with the Pmmn space group of this first 1/4-filled l…
A continuum model of crystalline solid equilibrium is presented in which the underlying periodic lattice structure is taken explicitly into account. This model also allows for both point and line defects in the bulk of the lattice and at interfaces, and the kinematics of such defects is discussed in some detail. A Gib…
We develop a theoretical framework for the diffusion of a single unconstrained species of atoms on a crystal lattice that provides a generalization of the classical theories of atomic diffusion and diffusion-induced phase separation to account for constitutive nonlinearities, external forces, and the deformation of th…
Grand canonical Monte Carlo (GCMC) simulations of ethylene physisorption on the basal plane of graphite are reported. The calculated isotherms are compared with experimental results at several temperatures. The maximum surface coverage studied is close to one monolayer. The ethylene molecules are described as six Lenn…
A thermodynamic framework (UNIQUAC model with temperature dependent parameters) is applied to model the salt-induced protein crystallization equilibrium, i.e., protein solubility. The framework introduces a term for the solubility product describing protein transfer between the liquid and solid phase and a term for th…