Materials Literature
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The quasielastic scattering of laser light from nematic MBBA is studied utilizing homodyne procedures. The results stem from a comprehensive study of the half widths and areas of the "slow mode" peaks together with their temperature and angle dependence. The data taken at small angles yield the temperature-dependent r…
A calorimetric technique was used to accurately determine the dielectric loss tangent of both additive−free and commerical grades of polyethylene at liquid−helium temperature. We found that the loss tangent of polyethylene often exhibits a broadened dielectric relaxation peak. Although this peak is centered in the kil…
An ESR study of the [RhCl6]4− center in single crystals of AgCl has been made. The g values and chlorine hyperfine interactions observed for the axial chlorines are consistent with a d7 configuration and localization of the odd electron largely in the 4dz2 orbital. The same species has been studied in γ-irradiated sin…
Abstract Fourier transform infrared spectra have been obtained for polyethylene irradiated in oxygen and nitrogen atmospheres. The spectra before and after irradiation have been compared by digital subtraction. The difference spectra are indicative of changes caused by irradiation. Crosslinking and chain scission reac…
Abstract We report on measurements of the Larmor frequency dependence of the proton spin relaxation time T 1 in the nematic and isotropic phase of p-azoxyanisole (frequency range: 3.8 kHz ≦ ωL/2 π≦75 MHz) . In both cases our results clearly support the Pincus-Cahane mechanism of spin relaxation by order fluctuations (…
Abstract Thermosetting arylimides were prepared by reaction of sulfone ether diamines with maleic anhydride followed by chemical imidization of the intermediate polyamic acid with acetic anhydride/sodium acetate. These arylimides could be thermally cured to afford heat stable systems possessing high glass transition t…
Polymethylmethacrylate specimens are loaded by a flat-ended punch, both by impact and using an Instron machine. The deformation is compared with that produced in similarly loaded titanium and copper specimens and with related work by other researchers. It is found in these experiments that deformation occurs in locali…
Abstract The layer structure of kaolinite from Twiggs, Georgia and fire-clay type kaolinite (Frantex B, from France), particle size separates 2–0·2 μ m was studied by high resolution electron microscopy after embedment in Spurr low-viscosity Epoxy media and thin sectioning normal to the (001) planes by an ultramicroto…
The substitution reactions of tetrakis(4-N-methylpyridyl)porphinecobalt(III)(CoTMpyP) with pyridine have been studied as a function of pH at 25° and an ionic strength of 0.5 M. The mechanistic pathway proposed for the thiocyanate substitution reactions is applicable to pyridine as well. A pyridine axial substituent ha…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFluxional, catalytically active metal cluster, heptakis(tert-butylisocyanide)tetranickelV. W. Day, R. O. Day, J. S. Kristoff, F. J. Hirsekorn, and E. L. MuettertiesCite this: J. Am. Chem. Soc. 1975, 97, 9, 2571–2573Publication Date (Print):April 1, 1975Publication History Pu…
Abstract Bei der Darstellung von koordinativ ungesättigten Cr(II)‐ Oberflächenverbindungen führt Variation von T akt und/oder T red zu unterschiedlicher Reaktivität der Produkte, bezogen auf gleichen Oberflächen‐Cr(II)‐Gehalt. Es wird ein Parameter Q definiert, der den (mittleren) „ungesättigten Charakter”︁ der Oberfl…
Abstract In the preceding paper, general equations were established for the motions of chains confined to a tetrahedral lattice. In the present paper, bond orientation correlation and autocorrelation functions are explicitly calculated for the case where only three‐bond elementary motions are considered. Effects due t…
Abstract The elastic free energy for a tetrafunctional network is here expressed as where λ 1 , etc., are the principal extension ratios relative to the state of reference (wherein 〈 r 2 〉 = 〈 r 2 〉 0 ), and C 1 , C 2 , and m are arbitrary parameters. The free energy of a swollen system is taken to be the sum G = G mi…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNitroxides. LXX. Electron spin resonance study of cyclodextrin inclusion compoundsJ. Martinie, J. Michon, and A. RassatCite this: J. Am. Chem. Soc. 1975, 97, 7, 1818–1823Publication Date (Print):April 1, 1975Publication History Published online1 May 2002Published inissue 1 A…
Abstract The relaxation kinetics of a staggering zipper model are presented, in which the formation of helical nuclei is regarded to be rate‐limiting and in which the sliding of strands along the helices is prohibited. Instead a realignment of staggered chains is only possible via complete uncoiling. While maintaining…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydrogen bonding interaction of some naturally occurring isomeric juglones with dioxaneS. B. Padhye and B. A. KulkarniCite this: J. Phys. Chem. 1975, 79, 9, 927–928Publication Date (Print):April 1, 1975Publication History Published online1 May 2002Published inissue 1 April 1…
Abstract Differential thermal analysis in hydrostatic apparatus yielded for K 2 CO 3 : solid‐liquid transition (905 ± 2°C intercept at 1 bar), 20.2 ± 0.6 deg kbar −1 slope and solid‐solid (421 ± 2°C), 16.8 ± 0.8 deg kbar −1 , to ∼5 kbar; Na 2 CO 3 : solid‐solid (485 ± 3°C), 15.5 ± 0.5 deg kbar −1 and solid‐solid (356…
A method is proposed for constructing in general form an analytic approximation to the energy distribution function g(ϵ) of spin waves in an ideal Heisenberg ferromagnet. The method is based on the construction of subspaces which are invariant under the Heisenberg operator, which enables one to express the function g(…
Abstract EPR and matrix ENDOR spectra have been examined for polyenyl radicals in γ‐irradiated PVF, PVF 2 , PVC, and PMMA polymers. Proton matrix ENDOR is observed for all four polymers, and fluorine matrix ENDOR for PVF and PVF 2 . By line shape analysis of the ENDOR spectra obtained under comparable conditions, delo…
Abstract ABS (acrylonitrile‐butadiene‐styrene) plastics are one of the most common two‐phase commercial polymer systems. They consist of a continuous rigid phase (styrene‐acrylonitrile co‐polymer) in which the elastomer phase (polybutadiene grafted with styrene and acrylonitrile) is finely dispersed in the form of sph…