Materials Literature
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We present a phenomenological theory describing the self-similar coarsening stage in the collapse of a long flexible homopolymer chain in a dilute solution upon a sudden quench. The approach is based on the “necklace” picture of the collapsing chain being composed of clusters separated by strands as demonstrated by co…
Orientation behavior of acrylate-based liquid crystalline (LC) networks containing different types of cross-links is studied and discussed. Cross-links incorporated by chemical reaction with cross-linking agent presumably distort LC order, whereas cross-links induced by γ-irradiation preserve and even stabilize the ne…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTLow Band Gap Cyanovinylene Polymers Based on EthylenedioxythiopheneGregory A. Sotzing, Christopher A. Thomas, John R. Reynolds, and Peter J. SteelView Author Information Center for Macromolecular Science and Engineering, Department…
We report the results of a computer simulation of the evolution of structure in a two component fluid consisting of a liquid phase and a dispersed colloidal phase subjected to a biaxial field. A biaxial field, such as a rotating field, can induce the organization of polarizable particles into two-dimensional sheets, i…
Posttransfer modification of preformed Langmuir-Blodgett films of poly(tert-butyl methacrylate) and poly(tert-butyl acrylate) by gaseous hydrochloric acid yields films with layered architecture of poly(methacrylic acid) and poly(acrylic acid), respectively. X-ray reflectivity and infrared spectroscopy confirm monolaye…
A model polymer−solid interface, aluminum- (Al-) carboxylated polybutadiene (cPBD), was designed to investigate the influence of the sticker group (−COOH) on the fracture energy ( G IC ). A model polymer, cPBD, was synthesized through high-pressure carboxylation of polybutadiene (PBD) and contained −COOH randomly dist…
The optical transitions of neutral and charged oxygen vacancies in the bulk and on the surface of MgO have been studied by means of first principles calculations. Using rather large cluster models representing the MgO F+ and F centers, oxygen vacancies with one and two electrons trapped in the cavity, respectively, we…
Reactions of semicrystalline poly(ethylene terephthalate) (PET) film with ester-selective reagents at the film−solution interface can be controlled to produce modified film samples containing a thin (less than ∼ 40 Å) surface layer of the reagent-induced functionality. Hydrolysis of PET yields a surface mixture of alc…
Thiolcapped CdTe nanocrystals (18 Å diameter) are investigated by extended x-ray absorption fine structure (EXAFS) measurements between 8 and 290 K at the Cd and Te K-edge. The different coordination sites of Cd in the particle core and at the surface are identified and are consistent with a CdTe particle core which i…
We have measured the magnetic susceptibility of single-crystal Cu_{1-x}Ni_xGeO_3 to study doping effects of the magnetic impurity (Ni^{2+} has S=1 spin) on the inorganic spin-Peierls (SP) material CuGeO_3. We observed the disappearance of the SP transition and the abrupt increase of the Neel temperature from 2.5 to 3.…
The effect of temperature on adsorption isotherms of Ar, N2, O2, C2H4, and CO2 on model mesoporous adsorbents (MCM-41) with different pore sizes (pore radius rp=1.2, 1.4, 2.1 nm) has been measured. The results clearly show that the hysteresis loop shrinks with increasing temperature and eventually disappears at the hy…
It has recently been shown that zirconium tungstate (ZrW2O8) exhibits isotropic negative thermal expansion over its entire temperature range of stability. This rather unusual behavior makes this compound particularly suitable for testing model predictions of a connection between negative thermal expansion and pressure…
Scientists have sought for over two decades to incorporate the necessary attributes of transparency, stability, and high nonlinear susceptibilities into optimized organic or organometallic chromophores for third-order nonlinear optical (NLO) applications. These investigations have provided an ever-expanding understand…
The streamer-to-spark transition is an important sub-process of the flashover of high-voltage apparatus. In this paper an investigation of this transition in an electrode gap of the order of 1 cm in dry air with a non-uniform field distribution is presented. Parameters such as the gap distance, polarity of applied vol…
We present results of a computer simulation of protein crystal growth based on the Monte Carlo random process and surface kinetics of a growing crystal, which includes site-dependent detachment and migration, and site-independent attachment processes. The results indicate that, if only monomers are included in the att…
We studied physiological conditions during the spinning of dragline silk by the garden cross spider, Araneus diadematus. Silk is converted from the liquid feedstock in the gland into a solid thread via a tapering tubular duct and exits at a spigot. The distal part of the tubule appears specialized for ion transport an…
The band structure theory of magnetism in 3d-4f compounds is reviewed. Among the open-shell electrons, a hierarchy of interactions is present which governs the intrinsic magnetic properties of these materials. Density functional theory (DFT) is an appropriate tool to describe and quantitatively investigate both ground…
The structural features of the interface between the cystalline and amorphous phases of Si solid are studied in simulations based on a combination of empirical interatomic potentials and a nonorthogonal tight-binding model. The tight-binding Hamiltonian was created and tested for the types of structures and distortion…
We have measured the magnetic susceptibilities of single crystals of Cu_{1-x}Zn_xGeO_3 with extremely low Zn concentration (x) lower than x=5x10^{-3} at very low temperatures to investigate the spin-Peierls and antiferromagnetic transitions. The results show that the undoped CuGeO_3 has no antiferromagnetic phase down…
The goal of this work was to design a ferromagnetically coupled Mn(2+)Ni(2+) species. For this, we attempted to combine nitro-nitrito and end-on azido bridges which are both known to be ferromagnetic couplers. This has led us to the compound of formula Mn(N(3))(4)[Ni(en)(2)NO(2)](2) (en = ethylenediamine). The crystal…