Materials Literature
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A new concept in initiator design using orthogonal protecting groups provides a versatile synthetic route to novel dendritic−linear AB, A 2 B, AB 2, A 2 B 2, and A 3 B 3 amphiphilic block copolymers. The A blocks are composed of the first- through third-generation dendrons from 2,2-bis(hydroxymethyl)propionic acid (bi…
Abstract A series of terpolymers were synthesized by oxidative polymerization of aniline, o ‐toluidine, and 2,3‐xylidine with three monomer ratios using ammonium persulfate as an oxidant in two acidic media. The yield and intrinsic viscosity of the terpolymers were studied by changing the polymerization temperature an…
Abstract Polarized Raman spectra of an oriented taurine single crystal were studied at temperatures ranging from 7 to 300 K. The results show that several bands present a linewidth increase characteristic of anharmonic effects, and that the band related to the CSH torsional mode splits at low temperatures. An abrupt w…
In this work we present a theoretical study on the possible use of quasicrystals as potential thermoelectric materials. By considering a suitable model for the spectral conductivity we show that high values of the thermoelectric figure of merit, beyond the practical upper limit $ZT=1,$ may be expected for certain quas…
Abstract A series of linear functionalized polyorganosiloxanes of the type Me 3 SiO[MeSiO(CH 2 ) n R] x (Me 2 SiO) y SiMe 3 , where n = 2, R = —(CH 2 )NMe 2 ; n = 1, R = —(CH 2 )OEt; n = 4, R = —(CH 2 )COOEt; n = 3, R = —(CH 2 )Me, have been prepared and characterized. Functional group loadings of ∼4 mol % ( x = 1, y…
We have performed molecular dynamics simulations of self-interstitial atom diffusion in pure \ensuremath{\alpha}-Fe and in a dilute Fe--1.0-at. % Cu alloy. We find that the presence of this oversized substitutional solute significantly alters the self-interstitial diffusion properties. We explain this through a mechan…
The interaction of ions and molecules with surface modes in cylindrical channels in solids is described on the basis of the dielectric formalism, starting with simple dielectric models and using also more realistic descriptions of the dielectric properties of various materials of experimental interest. The response of…
We have investigated the electronic and magnetic structures of Sr(2)FeMoO(6) employing site-specific direct probes, namely x-ray absorption spectroscopy with linearly and circularly polarized photons. In contrast to some previous suggestions, the results clearly establish that Fe is in the formal trivalent state in th…
Calculations using an analytic potential show that carbon nanocones can exhibit conventional cone shapes or can form concentric wave-like metastable structures, depending on the nanocone radius. Single nanocones can be assembled into extended two-dimensional structures arranged in a self-similar fashion with fivefold…
Compositionally modulated structures consisting of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ ferromagnetic (FM) layers $(x=0.33,$ 0.4, 0.48) and ${\mathrm{La}}_{1\ensuremath{-}y}{\mathrm{Ca}}_{y}{\mathrm{MnO}}_{3}$ antiferromagnetic (AF) layers $(y=0.52,$ 0.67, 0.75) were grown on $(001){\m…
We present a detailed ultrasonic study of the low-temperature nonequilibrium (transitional) phase diagram of ${\mathrm{H}}_{2}\mathrm{O}$ ice in the pressure range 0--1.7 GPa and temperature range 77--200 K. A continuous crossover from the thermodynamically driven $\mathrm{I}h$-II transition to the nonequilibrium scen…
This paper reports the unique influence of added [60]fullerene on the gelation ability of Zn(II) porphyrin appended cholesterols 5a − d . At 5 °C 5a with a (CH 2 ) 2 spacer gelated aromatic hydrocarbons such as benzene, toluene, and p -xylene (2.55 × 10 - 2 mol dm - 3 ), whereas at 20 °C these transparent gels were ch…
Zirconium substituted mesoporous SBA-15 molecular silica with Si/Zr ratios of 10, 20, 40, and 80 have been successfully synthesized at 373 K under microwave-hydrothermal conditions within about 2 h. The degree of framework substitution has been monitored by means of powder X-ray diffraction (XRD), nitrogen adsorption,…
A lamella-forming poly(ethylene oxide)- b -polystyrene (PEO- b -PS) diblock copolymer has been blended with a low molecular weight polystyrene (PS) homopolymer to form a miscible polymer blend. The PEO volume fraction is 0.32, and the order−disorder transition temperature ( T ODT ) of this blend is 175 °C. Therefore,…
Superhard cubic boron-carbonitrides $(c\ensuremath{-}{\mathrm{BC}}_{2}\mathrm{N})$ are studied with the use of the ab initio pseudopotential density functional method. The total energy, lattice constant, bulk and shear moduli, and electronic band structures as well as the electron density of states are calculated for…
A new class of bifunctional periodic mesoporous organosilicas (BPMOs) containing two differently bonded organic moieties in a mesoporous host has been synthesized and characterized. By incorporating bridge-bonded ethylene groups into the walls and terminally bonded vinyl groups protruding into the channel space, both…
We report various many-body theoretical approaches to the nonlinear decay rate and energy loss of charged particles moving in an interacting free electron gas. These include perturbative formulations of the scattering matrix, the self-energy, and the induced electron density. Explicit expressions for these quantities…
Abstract High‐quality Raman spectra were used for the characterization of alumina phases of gibbsite, bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm −1 in the hydroxyl stretching region. The spectrum of bayerite shows seven bands at 3664,…
The room-temperature luminescence of single CdSe/ZnS core−shell quantum dots is investigated by spectrally and temporally resolved confocal microscopy. A large (30 nm) blue shift is observed in the emission wavelength during illumination in air. In nitrogen, no blue shift is observed. The blue shift in air is ascribed…
When asked to explain the importance of the discovery of conducting polymers, I offer two basic answers: They did not (could not?) exist, and they offer a unique combination of properties not available from any other known materials. The first expresses an intellectual challenge; the second expresses a promise for uti…