Materials Literature
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A novel process is described for synthesizing high aspect ratio, controlled diameter mesoscale poly(phenolformaldehyde) fibres using the well defined channels of mesoporous silica as a mold and their extraction with the structure intact.
The equilibrium volumes and cohesive energies of Ti, Zr and Hf have been calculated using a full-potential (FP) linear-muffin-tin-orbitals (LMTO) method and the generalized-gradient approximation of Perdew and Wang. A structural phase stability analysis between hcp, ω and bcc structures shows a similar crystal structu…
1. INTRODUCTION The prediction of polymer crystallization behavior at a reasonable semiquantitative level of accuracy is important in assessing processability and performance. For example, in both polypropylene (PP) [1–3] and poly(ethylene terephthalate) (PET), the interplay of the effects of rheology and crystallizat…
A comparative study of the spectral-luminescent properties (at 293 K and 77 K) of meso-tetrakis(o-tolyl)porphyrin (o-TTP) and meso-tetraphenylporphyrin (TPP), and also meso-tetrakis(n-propyl)porphyrin (TPrP) in nonaqueous acid media has been carried out with the aim to reveal effects associated with the influence of m…
Electron-transfer reactions in an H-bonded assembly composed of a diacylaminopyridine bearing zinc porphyrin and 1,8:4,5-naphthalenetetracarboxylic diimide (Ka = 2.8 × 102 dm3 mol–1) in benzene occur with kCS = 4.1 × 1010 s–1 and kCR = 3.7 × 109 s–1, while the corresponding covalently linked model with a comparable di…
Nanometric particles of InP are readily prepared by the decomposition of the complex In(PBut2)3 at 167 °C in 4-ethylpyridine; the resulting materials show marked quantum confinement effects, and was investigated using optical absorption and photoluminescence spectroscopies, and transmission electron microscopy.
Ordering kinetics after quenching a block copolymer melt from the disordered state to the ordered state were studied by time-resolved, depolarized light scattering. A theoretical framework for relating the scattering patterns to the granular organization within the sample was developed. In some cases we found that ord…
A series of rhenium(I), zinc(II) and mercury(II) complexes of π-donor-substituted vinyl bipyridines [donor=4-R2N–C6H4–; 4-RO–C6H4–; (C5H5)Fe(C5H4–); (C5H5)Ru(C5H4–)] has been prepared and characterized by 1H NMR and UV-visible spectroscopy. The second-order nonlinear optical properties of bipyridyl ligands and of thei…
Benzyl 4-iodoperfluorobutanoate was synthesized by partial pyrolysis of perfluoroglutaryl chloride in the presence of potassium iodide followed by esterification. This compound gives access to mesogenic molecules with alkyl chain, perfluoroalkyl central bridge, and biphenyl moieties. Segregation of these chemical frag…
QCM showed that SiO2/poly(diallyldimethylammonium chloride) (PDDA) film assembly could be achieved in 2 s for 45 nm silica nanoparticle monolayers and 20 s for PDDA monolayers, with film integrity demonstrated by SEM and spectroscopic ellipsometry.
By using a surfactant-based synthesis strategy, we have earlier demonstrated that the polymerization and growth of silicate micellar assemblies at the air–water interface, under quiescent and dilute acidic aqueous conditions, yields free-standing sub-micron thickness hexagonal mesoporous silica films in which the chan…
A B S T R ACT : Infrared (IR) spectra of well-ordered kaolinites generally show four OH-stretching frequencies, near 3697, 3670, 3652 and 3620 cm i. Raman spectra of the same kaolinites mostly show an additional band near 3686 cm -~, which, in the coarsely crystalline Keokuk kaolinite, largely replaces the 3695 cm -I…
The crystal structures of four different conformers of the sterically encumbered porphyrins ZnDPP, H 2 DPP, and NiDPP are reported (DPP = 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin). In combination with two previously published structures of H 2 DPP and NiDPP, the crystallographic results illustrate the rema…
Abstract This study introduces the idea of the sharpness concept in relationship to the determination of scanning electron microscope (SEM) performance. Scanning electron microscopes are routinely used in many manufacturing environments. Fully automated or semiautomated SEMs as metrology instruments are used in semico…
New linear conjugated porphyrin polymers are synthesized by a palladium-catalyzed cross-coupling reaction of [5,15- bis(ethynyl)-10,20-bis(mesityl)porphyrin]zinc and diiodobenzene derivatives; enhanced solubility of the conjugated porphyrin polymers is achieved by attachment of long alkyl ether or dialkyl amide groups…
The so-called bias pretreatment allows the growth of heteroepitaxial diamond films by plasma chemical vapor deposition on silicon (100) surfaces. We present plan-view and cross-sectional transmission electron micrographs of the substrate surface at different phases of the bias pretreatment. These observations are augm…
The relationship between surface speciation and catalytic activity/selectivity during methanol oxidation on polycrystalline rhodium under ambient-pressure flow-reactor conditions was studied from 25 to 500 °C by means of surface-enhanced Raman spectroscopy (SERS) along with parallel mass spectrometric (MS) measurement…
We study the depletion interaction between spherical particles of radius R immersed in a dilute solution of rigid rods of length L. The computed interaction potential is, within numerical accuracy, exact for any value of L/R. In particular we find that for L ∼ R, the depth of the depletion well is smaller than the pre…
Abstract Meso-meso coupled diporphyrins were prepared from 5,10,15-trisubstituted zinc-porphyrins in high yields upon treatment with AgPF6 alone or with AgPF6 and I2.
Peptide-based polymers can be transformable hydrogels, elastomers, regular thermoplastics, or inverse thermoplastics, and can function as diverse molecular machines. When of the appropriate composition, these polymers exhibit hydrophobic folding and assembly transitions in the accessible aqueous range as the temperatu…