Materials Literature
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Wormlike dendrimers made of flexible and noninteracting segments were synthesized. Starting from a poly(methylhydrosiloxane) G 0 and using short propylsilane branches, the synthesis did not go beyond the second generation, as predicted from steric congestion. The starting polymer and the G 1 and G 2 dendrimers synthes…
Radiation induced grafting of acrylic acid onto polyethylene film was investigated. The grafted films rapidly adsorbed Cu2+, Cd2+, Th4+, and UO ions in high efficiency. The carboxylic acid groups on AAc-grafted PE film acted as a chelating site for the selected metal ions. Complex formation of metal ions and carboxyli…
The temperature-dependent resistivity behavior of carbon black–loaded polyethylene (PE) composites irradiated both at room temperature and 170°C above the PE melting point was studied. The irradiation doses were varied. At a given loading level, irradiation at room temperature corresponded to an energy treatment on a…
An analysis of the cylindrical brush of an isolated comb copolymer molecule, consisting of a semiflexible backbone and rodlike side chains, is presented. Using a mean-field approach and a simplyfying assumption, which is tested by computer simulations, we find that the persistence length of the brush, λ, scales as λ ∝…
Optical second harmonic generation (SHG) was used to study how mechanical rubbing modifies the surface structure of a polyimide (poly[4,4‘-oxydiphenilenepyromellitimide], PMDA-ODA) film and how the rubbed polyimide surface aligns a liquid crystal monolayer (4‘- n -octyl-4-cyanobiphenyl, 8CB) adsorbed on it. It was fou…
The Chandra spacecraft has been launched successfully on July 23, 1999. The payload consists of a high resolution X- ray telescope, two imaging detector systems in the focal plane and two transmission gratings. Each one of the two gratings can be put in the beam behind the telescope and the grating spectrometers are o…
Magnetic CoFe 2 O 4 spinel ferrite nanoparticles are synthesized by a microemulsion method using sodium dodecyl sulfate as the surfactant to form micelles. A statistical method of factorial design is used to establish a mathematical model from a series of synthesis experiments. This chemometric model quantitatively co…
The formation of alternating layers of positively charged gold and negatively charged silver colloidal particles on glass substrates via electrostatic interaction is described. The charging of the gold and silver colloidal particles is accomplished by self-assembly of 4-aminothiophenol (4-ATP) and 4-carboxythiophenol…
The thermochromic and solvatochromic properties of a series of fluorene-based conjugated polymers have been investigated. Both poly(2,7-(9,9-dioctylfluorene)) and poly(2,5-(thiophene)- alt -2,7-(9,9-dioctylfluorene)) have revealed interesting chromic properties which, on the basis of theoretical calculations, seem to…
Segment and domain orientation behaviors of a series of poly(butylene succinate) (PBS) –poly(tetramethylene glycol) (PTMG) segmented block copolymers containing different amounts of hard segment were studied with synchrotron small-angle X-ray scattering (SAXS) and infrared dichroic methods. Copolymers used in this wor…
K 2 MnSn 2 Se 6 ( I ), K 2 MnSnSe 4 ( II ), and K 2 Ag 2 SnSe 4 ( III ) were prepared by molten-salt (alkali-metal polyselenide flux) reactions at intermediate temperature (400−520 °C). Their crystal structures were determined by single-crystal X-ray diffraction techniques. Crystal data for I: space group P 4/ ncc, a…
Ce-doped BaTiO 3 (BTO:Ce) thin films prepared on MgO (100) substrates by pulsed laser deposition (PLD) at oxygen pressure of 1.2×10 -3 and 17 Pa have been studied by micro-Raman spectroscopy, x-ray diffraction (XRD) and atomic force microscopy (AFM). The film deposited at lower oxygen pressure has a larger lattice par…
The potential use of novel poly(sulfobetaine) copolymers as antibioadherent coatings was investigated using Pseudomonas aeruginosa as a model microorganism and human macrophages and 3T3 mouse embryonic fibroblasts. Two well-defined statistical copolymers with narrow molecular weight distributions were prepared by grou…
The theory of atoms in molecules (AIM) defines bounded atomic fragments in real space that generate transferable atomic properties. As part of a program that investigates the topological partitioning of electromagnetic properties based on the electron density, we have calculated the exact atomic electrostatic potentia…
We calculate the widths, migration barriers, effective masses, and quantum tunneling rates of kinks and jogs in extended screw dislocations in copper, using an effective medium theory interatomic potential. The energy barriers and effective masses for moving a unit jog one lattice constant are close to typical atomic…
Charged poly(amidoamine) (PAMAM) dendrimers are used to create organic−inorganic hybrid colloids in aqueous solution. The formation of gold colloids upon reduction of a gold salt precursor serves as a model reaction to study the influence of reaction conditions and dendrimer generation on the resulting nanostructures.…
In the light of recent experimental as well as theoretical studies, we summarize our present understanding of polar oxide surfaces and examine fundamental issues regarding their stability. The focus is on the surface atomic configurations (relaxations, reconstructions, non-stoichiometry, etc) obtained under specific p…
Addition–elimination reactions produce the salts of hexanitroisobutene dianions from the potassium salt of 2,2-dinitroethanol and trinitromethane. The picture shows an ORTEP representation of the dianion, which clearly features the isobutyl core and six bound nitro groups.
A multiplex electronic switch on the molecular level has been realized by using a tetranuclear FeII complex of the [2×2] grid type. The four metal ions can be switched stepwise between their high-spin and low-spin states by temperature, pressure, and light, thus representing a triple level, triple switch system as ill…
Microstructural evolution induced by scanned laser annealing (SLA) of Cu interconnects was found to produce unique large-grained “bamboo” grain structures, with bamboo grain lengths up to ten times the linewidth. These bamboo grain lengths are shown to depend on the scan rate and laser power. By comparing results from…