13C NMR spin-lattice relaxation in solid poly(methyl methacrylate)

Summary ¹³C spin-lattice relaxation rates R₁ in samples of solid PMMA have been measured with CP MAS NMR. Isotactic, atactic, syndiotactic, and the 12 i-s PMMA complex were measured, along with atactic samples containing bisdioxan or the monomer as a plasticizer. The reorientation of the -methyl protons is the dominant relaxation source for the methylene, -methyl and quarternary carbon nuclei. Increased mobility of the polymer in the presence of a plasticizer is not reflected in significant changes in R₁.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, July 20–23, 1981     

Identification of sex pheromones of two sibling species in dingy cutworm complex,Feltia jaculifera (GN.) (Lepidoptera: Noctuidae)

The sex pheromone components of the two sibling species of the dingy cutworm that occur on the prairies of western Canada were identified in abdomen-tip extracts from calling female moths. Three monounsaturated acetates, (Z)-7-dodecenyl acetate, (Z)-9-tetradecenyl acetate, and (Z)-11-hexadecenyl acetate, are common to both species in ratios of 100133 for species A and 0.30.5100 for species B. The most effective synthetic blends for the attraction of male moths in the field consisted of these three components in ratios of 1010 at 8.8g/lure for species A and 112000 at 500g/lure for species B. The addition of Z5-12Ac to either blend reduced the catches and the addition of Z7-12OH orZ11-16OH to the three-component blend reduced the catches of species B males. The species are morphologically indistinguishable, but the identity of the males attracted to the synthetic blends could be confirmed by their antennal responses to a test blend of the three components using a GC-EAD system. Both synthetic attractant blends are competitive with females and will be useful for studying the distribution, biology, and relative abundances of the two species.Contribution no. 3879005 of the Lethbridge Research Station.     

New polymer syntheses

Summary Various poly(ether sulfide)s were prepared by polycon-densation of 4-mercaptophenol or silylated 4-mercaptophenol with 2,6-dichloropyridine or 3,6-dichloropyridazine. A two step and an one-pot procedure were compared. The poly-(ether-sulfide)s were characterized by elemental analyses, inherent viscosities, ¹³C-NMR spectroscopy, gel-permeation chromatography and DSC-measurements.     

Interactions between PVC and solvents by longitudinal nuclear relaxation times

PVC/aliphatic ketone systems were investigated by NMR relaxation times such as proton and carbon-13 spin-lattice relaxation time (T1) and proton spin-lattice relaxation time in the rotating frame (T1). The proton T1 results showed that these systems are homogeneous, while proton T1 indicates the existence of more than one domain.     

Pulsed electrodeposition of zinc in magnetic fields: diffusion layer relaxation followed by laser interferometry

The pulsed galvanostatic deposition of zinc was carried out in the presence and absence of an externally applied magnetic field of 0.43 T. The concentration time profiles and the relaxation of the cathodic diffusion layer during the pulsing sequence have been determined by using laser interferometry. When, in the pulsing mode, longer off periods compared to the on periods were used, significantly greater relaxation of the diffusion layer was observed. The fringe shift time profiles for the electrodes kept in the vertical or anode over cathode positions are influenced by the hydrodynamic effect; the magnetic field effect on the relaxation of the diffusion layer has been observed. The electrodeposited Zn has been analysed by scanning electron microscopy; the Zn deposit obtained by pulsed current electrolysis in the cathode over anode position is dense and uniform.     

Variation in semiochemical-mediated prey-predator interaction:Ips pini (Scolytidae) andThanasimus dubius (Cleridae)

The bark beetleIps pini (Say) displays variation in its response to and production of enantiomeric blends of its pheromone ipsdienol. One of the principal predators ofIps pini isThanasimus dubius (F.), which uses ipsdienol as a kairomone for prey location. During 1988 and 1989, in Wisconsin and Michigan, the response of both species to a range of enantiomeric blends of ipsdienol was investigated. Blends tested had the following ratios of the (S)-(+) to (R)-(–) enantiomers: 3%97%, 25%75%, 50%50%, 75%25%, and 97%3%. Either75% (+) 25% (–) or 50% (+) 50% (–) ipsdienol captured the mostIps pini in both years at both sites. The 25% (+)75% (–) blend also caught moreIps pini than the control during both years at both sites. All blends tested were attractive toThanasimus dubius in both years at both locations. Blend preferences of both species were variable and labile at both sites. Response patterns of both species in Wisconsin were different from those in Michigan each year. Furthermore, response patterns of both species to the ipsdienol blends changed from 1988 to 1989 at both locations. A genetic component to this variation would permit predator-prey coevolution, as well as the development of resistance byIps pini to management strategies based on mass-trapping with single blends.     

Sonovoltammetry at platinum electrodes: surface phenomena and mass transport processes

Application of simultaneous ultrasound to representative solution-phase reversible voltammetric couples produce a step-shaped voltammogram at platinum electrodes of both macro and micro dimensions. The limiting current increases with ultrasonic power, but is not markedly affected by ultrasonic frequency in the 20–800kHz region. In contrast the complex voltammetry of a platinized platinum electrode surface within the hydrogen adsorption regime in aqueous acid medium is very little affected by sonication. Factors affecting the reproducibility of sonoelectrochemical experiments when employing ultrasonic sources are discussed.Author to whom correspondence should be addressed     

The effect of carbon black filling and cross-linking in stretched SBR networks: a 2H-NMR study

Summary The line splitting v in ²H-NMR spectra of deuterated benzene in stretched crosslinked SBR depended linearly on the classical stretch term ² – 1/ for samples with and without carbon black filling. The ratio LS = v/(² – 1/) was measured in dependence on the solvent fraction . The extrapolated value L of this ratio at =0 gave a linear dependence on the inverse molecular mass 1/M_c of inter-crosslink chains. This was expected according to a simple model of chain dynamics and offers a further NMR-method for M_c-determination even in filled networks. However, the slope of the L(1/M_c)-line increases with an addition of carbon black which indicates a higher molecular order. Three reasons for this could be discussed. However, one of them is preferable.     

Convective Regime of Filtration Combustion of Energetic Materials in a Cocurrent Flow of Their Combustion Products

The convective regime of filtration combustion of energetic materials in a cocurrent flow of their combustion products is studied using a model with extremely simplified kinetics and heat transfer, which shows instability of the process. It is shown that the more accurate twotemperature model describes a steadystate regime. In this regime, the gas temperature on the hot boundary of the heating zone is well below the combustion temperature, and the solidphase temperature is well below the temperature proposed in recent studies on this topic. It is pointed out that the twotemperature approach is unjustified and intragranular nonisothermicity must be taken into account for convective regimes. It is shown that the threetemperature model, which takes into account this effect, does not give a stable steadystate solution.     

Studies on electrical conductivity of gamma irradiated polyaniline

Summary de electrical conductivity at surface of -irradiated polyaniline (PAn) has been studied. EPR spectroscopic results indicate that the variation of spin concentration is consistent with the increase of _de. Electrical conductivity (_de) versus temperature (T) characteristics of unirradiated and irradiated PAn were performed, which demonstrate that the unirradiated curve can fit to ln_deT₁, while the irradiated curve fit to ln_deT_1/4.     

Synthesis of soluble polyarylenes containing alternating 4,4′-(1,1′-binaphthyl) and 4,4′-(3,3′-diphenyl)biphenyl structural units

Summary The synthesis and Ni(0) catalyzed homocoupling polymerization of 4,4-bis[5-(trifluoromethanesulfonyloxy)-2-biphenylyl]-1, 1-binaphthyl (9) are described. This polymerization reaction produces a soluble polyarylene containing alternating 4,4-(1,1-binaphthyl) and 4,4-(3,3-diphenyl)biphenyl structural units.     

Lamellar Morphology of Poly(3-hydroxybutyrate)/Poly(ethylene oxide) Blends as Studied via Small Angle X-ray Scattering

The lamellar morphology of a melt-miscible blend consisting of two crystalline constituents, poly(3-hydroxybutyrate) (PHB) and poly(ethylene oxide) (PEO) have been investigated by means of small angle X-ray scattering (SAXS). The blend was a crystalline/amorphous system when temperatures lay between the melting point of PEO (ca. T _m ^PEO=60C) and that of PHB (ca. T _m ^PHB=170C), while it became a crystalline/crystalline system below T _m ^PEO. The crystalline microstructures of the blends were induced by two types of crystallization history, i.e. one-step and two-step crystallizations. In the one-step crystallization, the blends were directly quenched from the melt to room temperature to allow simultaneous PHB and PEO crystallization. The two-step crystallization involved first cooling to 70C to allow PHB crystallization for 72 h followed by cooling to room temperature (ca. 19C) to allow PEO crystallization. In the crystalline/crystalline state, two scattering peaks have been observed in the Lorentz-corrected SAXS profiles, irrespective of the crystallization histories, meaning that crystallization created separate PHB and PEO lamellar stack domains. One-step crystallization yielded lamellar stack domains containing almost pure PHB and PEO lamellae. Two-step crystallization generated almost pure PHB lamellar domains and the PEO lamellar domains with inserted PHB lamellae. In the crystalline/amorphous state, the composition dependence of the amorphous layer thickness (l _a), the presence of zero-angle scattering, and the volume fraction of the PHB lamellar stack (_s) revealed that both one-step and two-step crystallizations, generated the interfibrillar segregation morphology, where the extent of interfibrillar segregation of amorphous PEO increased with increasing PEO content.     

Synthesis of statistical polydiene networks by reaction of liquid polyenes with telechelic siloxanes

The present investigation concerns the synthesis of statistical networks similar to vulcanized rubber. We have used liquid precursor polymers: polybutadiene (PB) and polyisoprene (PI) with telechelic siloxanes. The reactivity of the polydienes can be classified as follows: PB units 1,2 PI units 3,4 PI units 1,4 0. The network formation is a function of the ratio R = nb, of pendent double bonds/nb. of SiH. For R 1 the networks are rather hard and brittle, for 8 R 10 they are soft and elastic, whereas for R 16 the gels obtained are very soft and sticky.     

Synthesis of poly[(silanylene)thiophene]s

Poly[(silanylene)thiopene]s, copolymers with alternating thiophene, 2,2-bithiophene, or 2,2:5,5-terthiophene and mono-, di-, or tetrasilanylene units, were prepared by condensation of the dilithium salts of the thiophenes or the bis(2-thienyl)silanes with ,-dichlorosilanes in diethylether. The polymers were characterized with¹H,¹³C, and²⁹Si NMR, UV, IR, GPC, TGA, and elemental analyses. UV absorption maxima of these polymers all show a red shift with increasing length of the polymer backbone, suggesting that conjugation occurs through the combined -Si and -thiophene backbone.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

On the structure of the activated iron catalyst for ammonia synthesis

The contribution focuses on a brief account of the activation of iron oxide precursors to ammonia synthesis catalysts and discusses the question as to why normal iron is so inferior in catalytic performance compared to ammonia iron. The combination of microstructural analysis with kinetic observations allows the conclusion that the microtexture of ammonia iron is with a platelet morphology different from isotropic iron. The role of all additives in the generation of the platelet form is examined. The presence of oxygen, which was speculated to be beneficial for the reaction under certain conditions, was found to be detrimental for the catalytic performance under the present testing conditions.     

Location of Mn in MnAPO‐11: influence of synthesis from aqueous and non‐aqueous media

MnAPO11 samples were synthesized from aqueous (MnAPO11(A)) and ethylene glycol (MnAPO11(NA)) media. The crystallinity of the samples was more when the synthesis was carried out in ethylene glycol. Chemical and thermogravimetric analyses reveal greater incorporation of Mn in the framework of MnAPO11(NA) than in MnAPO11(A). At least five different types of Mn(II) species are detected in the samples by ESR. The studies suggest that Mn is more homogeneously distributed in MnAPO11(NA) than in MnAPO11(A).     

Specific features of the phase transformations occurring during the sintering process of the beta-alumina based ceramics and their properties

Conclusions During the sintering process of beta-alumina obtained using the method of plasmochemical synthesis, the structural transformation occurs and it is accompanied by the separation of the excess Na₂O and the formation of an intergranular meltlike phase that is saturated with sodium and is characterized by high dielectric properties.The quantity of the meltlike phase and the magnitude of the /( + ) ratio determine the degree of stabilization (stability) and the final resistivity of the material and depend on the initial chemical composition and the heating rate maintained during the sintering process.It was shown that when the duration of residence of the material in the hot zone of the furnace is increased or when the specimens sintered maintaining high heating rates are subjected to additional heat treatment, one observes the occurrance of the reverse structural transformation that is characterized by an increase of the phase ratio /( + ) 1, a reduction in the quantity of the meltlike phase right up to its complete disappearance, and a decrease of the electrical resistivity of the material.In the materials having a large excess quantity of sodium oxide, the process of crystallization of the intergranular NaAlO₂ phase occurs simultaneously with the second phase transformation.The best ceramic and electrophysical parameters were obtained when sintering the material contained 7.9% Na₂O.Translated from Ogneupory, No. 3, pp. 13–18, March, 1990.     

Prediction of Reverse Relaxation and Deformation—Recovery Processes in Synthetic Fibres

Use of force and geometric deformation variants of the nonlinear-hereditary viscoelasticity equation for prediction of complex processes by calculation is examined on the example of deformation-recovery and reverse relaxation processes in Lavsan synthetic fibres. A comparison of the calculated and measured values allows recommending the method of calculated prediction in which an elementary function — the normalized arctangent of the logarithm of the reduced time serves as the normalized relaxation or creep function.     

The aqueous thermal polycondensation of asparagine and isoasparagine and the structure of polyaspartic acid

Summary Both asparagine and isoasparagine were converted into polyaspartic acids by refluxing the corresponding aqueous solutions at neutral pH in the presence of a salt. The properties of the resulting polyaspartic acids were studied. The dissociation behavior of the carboxyl groups in the polypeptides were studied by the potentiometric titration. The analysis of the titrational data was performed by a modified Speakman's method. The analysis show that both polyaspartic acids prepared from asparagine and isoasparagine have - and -aspartyl residues and the ratio of - and -aspartyl residues is 75 2585 15. A possible mechanism for the formation of - and -aspartyl residues in the polymer was discussed.     

Molybdenum nitride for the direct decomposition of NO

The physico-chemical properties of passivated -Mo₂N have been investigated. The material showed high activities for NO direct decomposition: nearly 100% NO conversion and 95% N₂ selectivity were achieved at 450C. The amount of O₂ taken up by -Mo₂N increased with temperature rise and reached 3133.9 molg^–1 at 450C; we conclude that there formation of Mo₂O_xN_y occurred. This oxygen-saturated -Mo₂N material was catalytically active: NO conversion and N₂ selectivity were 89 and 92% at 450C. We found that by means of H₂ reduction at 450C, Mo₂O_xN_y could be reduced back to -Mo₂N and the oxidation/reduction cycle is repeatable; such a behaviour and the high oxygen capacity (3133.9 molg^–1) of -Mo₂N suggest that -Mo₂N is a promising catalytic material for automobile exhaust purification.