Critical solution point and chain dimension of branched-polystyrene solutions

Summary Critical solution point and chain dimension were measured for branched polystyrene(BPS) in solution as a function of molecular weight(M) and compared with those for linear polystyrene(LPS). The critical concentration _c of BPS was quite different from that of LPS at a fixed M, but the same at a fixed overlap-concentration ^*, i.e., plots of _c vs. ^* fall on a single straight line for both BPS and LPS (gf_c ^*). Reduced critical temperature _c defined by gt_c=(–T_c)/ [T_c: critical temperature, : the -temperature] was related to _c as _{c c} ² for BPS, whereas _{c c} for LPS.     

Note of the estimation of the Θ temperature and Ψ parameter from the critical temperature data

Summary Critical values of the polymer volume fraction _2,c and the interaction parameter _c have been computed for the case that the equation for the chemical potential of solvent contains terms _{c 2} ³ and _{c 2} ⁴ in addition to ₂ ² . For 0 _c 1/3, the limits for infinite chain length are _2,c = 0 and _c = 0.5. Quite different results are obtained for _c > 1/3, _2,c being finite and _c lower than 1/2. Conclusions for the estimation of the temperature and the entropy-of-dilution parameter are discussed.     

Change in degree of polyamidation of polycaproamide during orientation stretch

Conclusions The effect of stretch ratio, the ratio of stretch ratios in the cold and hot zones, and of the relative viscosity of polycaproamide on the degree of its breakdown during stretching have been examined.The degree of breakdown decreases if the viscosity stays within the range 3.25–3.35, and the stretch ratio in the cold zone is the maximum possible.Translated from Khimicheskie Volokna, No. 5, pp. 26–27, September–October, 1983.     

Variable‐temperature IR spectroscopic studies of CO adsorbed on Na‐ZSM‐5 and Na‐Y zeolites

CO interacts with extraframework alkali metal cations (M⁺=) of zeolites to form both M⁺CO and M⁺OC species. By using variabletemperature FTIR spectroscopy, these Cbonded and Obonded species were found to be in a temperaturedependent equilibrium. For the same cation, the difference in interaction energy depends upon the zeolite framework. Thus, for the equilibrium process ZNa⁺=CO ZNa⁺OC, where Z represents the zeolite framework, H ⁰ was found to take the values 3.8 and 2.4 kJ mol^– for CO/NaZSM5 and CO/NaY, respectively. The Cbonded species show always the highest cation–CO interaction energy.     

Lean NOx catalysis over alumina‐supported catalysts

aluminasupported catalysts show promise as lean NO_x catalysts. The role of alumina in influencing the structural and chemical properties of the active phase supported on it is discussed using some effective aluminabased lean NO_x catalysts. These include Ag/Al₂O₃, CoO_x/Al₂O₃ and SnO₂/Al₂O₃. Alumina plays an important role in stabilizing Ag in the oxidic phase and cobalt in the 2+ oxidation state. For SnO₂/Al₂O₃, alumina increases the SnO₂ surface area. On both Ag/Al₂O₃ and SnO₂/Al₂O₃, alumina also participates actively in the NO_x reduction reaction. An active organic intermediate is formed on Ag or Sn oxide which reacts with NO_x subsequently on alumina to form N₂.     

Dynamics of Phase Transitions in the SHS of a 3Cu–Al Powder Mixture in the Regime of Thermal Explosion

The paper reports results of dynamic xray photography of selfpropagating hightemperature synthesis of a 3Cu–Al powder mixture in the regime of thermal explosion. The stages of formation of the final product are considered, beginning with the heating of the starting mixture and interaction of its components and ending with phase transitions during cooling of the product — intermetallides Cu₉Al₄ and Cu₃Al, which are the main components of Cu based tribotechnical materials. It is shown that upon heating in the temperature range of 550 – 590°C, the intensity of diffraction lines of Al drops to the background level. The exothermicreaction of synthesis of the intermetallide is initiated at a temperature of 610 – 630°C. In the period of sharp increase in temperature to 1040°C, the presence of the starting copper and the newly formed hightemperature phase with the Cu₉Al₄ tructure are detected simultaneously in the combustion wave. When cooled to 300$°C, the material contains two cubic phases — Cu₉Al₄ and an solid solution of Al in Cu. Further cooling is accompanied by formation and increase of peaks of the Cu₃Al phase with an orthorhombic lattice. The phase composition of aluminum bronze produced by SHS with combustion in the regime of thermal explosion is not in equilibrium.     

Kinetics and Mechanism of Copolymerization of α-terpineol with Methylmethacrylate in Presence of Azobisisobutyronitrile as an Initiator

The radical copolymerization of -terpineol with methyl-methacrylate in xylene at 80±0.1C for 50 minutes in the presence of azobisisobutyronitrile (AIBN) follows ideal kinetics and results in the formation of a functional and random copolymer. The activation energy is 33 KJ/mole. The IR spectrum and NMR spectra of the copolymer(s) shows the bands at 1750 and 3400 cm^–1 for ester group of methylmethacrylate and alcoholic group of -terpineol and peaks at 3 to 4 for methoxy group and at 6.5 to 7.5 due to alcoholic group of methylmethacrylate and -terpineol repectively. The values of reactivity ratios, calculated by Kelen–Tüdos method, are r ₁ (MMA) = 0.18 and r ₂ (-terpineol) = 0.046. The Alfrey-Price; Q–e parameters for -terpineol has been calculated as 0.149 and 2.486. The mechanism of copolymerization has been elucidated and it is concluded that the double bond present in the monocyclic ring of -terpineol is an active site for copolymerization and the alcoholic group of -terpineol remain to give functional copolymer.     

Additional male mediterranean fruitfly (Ceratitis capitata wied.) Attractants from Angelica seed oil (Angelica archangelica L.)

Two sesquiterpene hydrocarbons, -copaene and -ylangene, were isolated from bioactive fractions of angelica seed oil and were shown by field bioassays to be attractive to the male Mediterranean fruit fly. Their relative attractiveness, compared with the(+)-and (–)--copaene enantiomers, are: (+)--copaene>angelica -copaene>angelica -ylangene>(–)--copaene. The enantiomer ratios for the two compounds are: -copaene, 61.4% (+), 38.6% (–); -ylangene, 91.9% (+), 8.1% (–).trans--Bergamotene was also isolated from the same fractions, but in sufficient quantity for bioassay [enantiomer ratio: 95.7% (+), 4.3% (–)].     

Chemistry of Combustion Waves in Substances with a Complicated Structure of Reagent Molecules. 1. Structure of the Front of Rich Isopentane Flame

Results on the structure of the lowtemperature relaxation zone of the front of a laminar Bunsen flame of isoC₅H₁₂ (2methylbutane) under atmospheric pressure are presented. The flame of a premixed mixture isoC₅H₁₂ + O₂ + Ar with a fueltoair equivalence ratio of 1.7 is examined. The mass fluxes, total rates of reactions of matter consumption and expenditure, balance of substances, and profiles of bulk heatrelease rates are calculated on the basis of the experimental concentration and temperature profiles. The results obtained indicate that there is a vast region of lowtemperature conversion of isopentane in the flame front. It is found that only part of the products sampled by the microprobe from different points of the flame front results from transformations in the lowtemperature region, namely, oxygen, isopentane, water, carbon monoxide, propane, methane, and methanol. Ethylene, propylene, hydrogen dioxide, and formaldehyde are present in the lowtemperature zone in insignificant amounts; they are secondary products of conversion of methyl and propyl radicals. It is assumed that the observed feature is a result of the competing interaction of two mechanisms of fuelmixture conversion: selfcatalysis and thermal selfacceleration. Based on the previously suggested mechanism of oxidation pyrolysis by the scheme of intramolecular quadratic destruction, experimentally observed fragmentation of the isopentane molecule is demonstrated. In contrast to npentane, formation of methyl alcohol has been found in isopentane convection products.     

Reductive transamination of methoxyacetone with benzylamine over Pd/SiO2 catalyst modified with anchored chiral compounds

Methoxyacetone was transaminated with benzylamine to methoxyisopropylamine over a Pd/SiO₂ catalyst modified with Lalaninol or Lphenylalaninol covalently anchored to the surface of the support via an organosilicon spacer group. In the first step of transamination a Schiff base was formed from the ketone and benzylamine, and then it was hydrogenated in the second step on the chirally modified Pd/SiO₂ catalysts to an asymmetric secondary amine (Nbenzylmethoxyisopropylamine). In the third step the hydrogenolysis of the asymmetric secondary amine resulting in methoxyisopropylamine and toluene was carried out over a 10 wt% Pd/C catalyst. The highest enantiomeric excess of (S)methoxyisopropylamine was observed in cyclohexane (ee = –20–21%) using anchored Lalaninol as a chiral modifier.     

Electron Transfer in Ferrocene-containing π-conjugated Polymers

We describe here our recent research on -conjutgated organometallic polymers containing ferrocenyl groups. Internuclear electronic interactions through the -conjugated spacer display unique redox and optical properties. The dependence of the redox properties on the number of ferrocene moieties in oligo(1,1-ferrocenylene)s were analyzed by the neighboring-site interaction model. The electronic structure in the mixed-valence states of biferrocene and terferrocene were estimated using the infrared (IR) spectra. Intervalence-transfer (IT) bands in the mixed-valence states of oligo(1,1-ferrocenylene)s were rationalized by taking into account the change in neighboring-site interaction by photo-electron transfer. Near-IR photoconductivity was found for the charge transfer complex of oligo- and poly-(1,1-ferrocenylene)s with tetracycanoethylene (TCNE). Redox and optical properties of azo-bridged ferrocene oligomers and a polymer was also analyazed based on the neighboring-site interaction model. Metallacyclization reaction of para-bis(ferrocenylethynyl)benzene with CpCo(PPh₃)₂ affforded a ferrocene-containing cyclobutadienecobalt polymer, of which redox property indicates strong intra-unit and weak inter-unit interactions.     

On the nature of the active state of silver during catalytic oxidation of methanol

Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques.     

Studies concerning charged nickel hydroxide electrodes IV. Reversible potentials in LiOH,NaOH, RbOH and CsOH

The variation of reversible potential E_r with log a_moh and has been studied for several nickel hydroxide/oxyhydroxide couples in various alkali hydroxides. Both activated and deactivated -phase couples show only a small dependence ofE _r with log_moh (or where known) in LiOH, NaOH, RbOH and CsOH electrolytes. The change in MOH content on oxidation/reduction is found to be about 0.1 mol MOH per two-electron transfer and is the same as found previously in KOH. These results confirm that the bulk oxidized -phase lattice is devoid of alkali cation although a small quantity may be adsorbed by the surface. On the other hand both activated and deactivated /-phase couples show a marked dependence of 0.45 mol MOH per two-electron transfer in LiOH, NaOH and RbOH (at concentrations > 0.5 m), also in good agreement with earlier data for KOH. On the basis of these results a general stoichiometry can be inferred for the -phase, namely M_0.32NiO₂ · 0.7H₂O where M=Li⁺, Na⁺, K⁺ or Rb⁺. Measurements imply that the Cs⁺ ion or the Rb⁺ ion at low concentration (<0.5 m) do not enter the interlayer structure of the -phase. This behaviour is thought to be related to the low Rb-O and Cs-O bond strengths afforded by the -phase structure.     

Application of the accelerated Tafel plot technique to corrosion kinetics: Role of double layer through simulation

Results on the simulated -t transient response of an actively corroding system under accelerated Tafel plot (ATP) conditions have revealed the influence of input parameters (i, ) and system parameters (C _dl,i _corr andb) and explained the observed dependence of kinetic parameters (arrived at on the basis of the intercept-slope method) on in certain time domains. New improved methods, which eliminate such dependence and give uniform corrosion rate data over all time domains, are described in the paper.Nomenclature ATP accelerated Tafel plot - transfer coefficient - b Tafel slope (V) - C _d double layer capacitance (F cm^–2) - i initial value of the exponentially decaying current (A) - E _c corrosion potential (V) - overpotential (V) - n overpotential corresponding to maximum in -t transient (V) - F Faraday constant (C mol^–1) - i _corr corrosion current density (A cm^–2) - n number of electrons involved in charge transfer step - p intercept of ATP (V) - R gas constant (JK^–1 mol^–1) - R _p polarization resistance ( cm²) - S slope of ATP, i.e. d/dt (V) - S _av average of theS values at > _el (V) - S _meas slope of the linear -t region, i.e. d/dt (Vs^–1) - T temperature (K) - t time (s) - t _m time corresponding ton _m in the -t transient (s) - time constant of the exponentially decaying current pulse (s) - _el electrode time constant given byR _p C _d (s)     

Effects of chloride, bromide and iodide ions on internal stress in films deposited during high speed nickel electroplating from a nickel sulfamate bath

The effects of chloride, bromide and iodide additions on the internal stress developed in nickel films deposited during high speed electroplating from nickel sulfamate baths operated close to the nickel ion limiting current density were investigated. The variations in internal strain in the films were detected in situ using a resistance wire-type strain gauge placed on the reverse side of the copper substrate. The film resistance on the as-plated electrodes was measured using an electronic current interrupter technique. The effects of chloride, bromide, and iodide additions could be classified into two groups: (a) chloride and bromide ions, and (b) iodide ions. For chloride and bromide additions over the concentration range of 0.1 to 0.5M, the nickel deposits exhibited a block- and pyramid-like texture with a (200) crystal orientation. The internal tensile stress developed in 20m thick nickel films deposited in the presence of these two halides was as low as 140–170MPa. Conversely, for additions of iodide, at iodide concentrations greater than 0.1M the deposited nickel exhibited a fine granular texture of disordered crystal orientation. The internal tensile stress developed in 20m thick nickel films deposited from these latter baths tended to rise with increasing iodide concentration to values considerably higher than those observed at similar concentrations of NiCl₂ or NiBr₂.     

Flow-through and flow-by porous electrodes of nickel foam Part III: theoretical electrode potential distribution in the flow-by configuration

This paper deals with the theoretical potential distribution within a flow-by parallelepipedic porous electrode operating in limiting current conditions in a two-compartment electrolytic cell. The model takes into account the influence of the counter-electrode polarization and of the separator ohmic resistance. The results show that the design of the porous electrode requires the knowledge of the solution potential distribution within the whole cell volume.Nomenclature a _c specific surface area per unit volume of electrode - C ₀ entrance concentration (y=0) - C _s exit concentration (y=y ₀) - E electrode potential (= _M – _S ) - E _o equilibrium electrode potential - F Faraday number - i current density - mean mass transfer coefficient - K parameter [a _ea zFi _oa/(_a RT)]^1/2 - L porous electrode thickness - n number of terms in Fourier serials - P specific productivity - Q volumetric flow-rate - mean flow velocity based on empty channel - V constant potential - V _R electrode volume - x thickness variable - X conversion - y length variable - y ₀ porous electrode length - z number of electrons in the electrochemical reaction Greek symbols parameter - parameter - ionic electrolyte conductivity in pores - _S solution potential - _M matrix potential ( _M = constant) - parameter [=n/y ₀ - parameter [=+K] - overpotential Suffices a anodic - c cathodic - eq equilibrium - s separator - S solution     

13C- and 23Na-NMR investigations on alkali cellulose

Summary Solid state ²³Na- and ¹³C-NMR spectra of alkali cellulose are presented as a function of NaOH-concentration of the steeping lye, steeping temperature and amount of adhering lye (press factor). Results are discussed with regard to chemical binding of NaOH to the cellulose chain in the system cellulose/ NaOH/H₂O.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, CSSR, July 20–23,1981     

Methodological setup to study allelochemical translocation in radish seedlings

[Ring-U¹⁴C] p-hydroxybenzoic acid (POH) translocation during radish germination and early seedling growth was studied to compare two culture conditions (sterile/non-sterile) and two modes of POH extraction (ethanol/oxidizing). Quantification of POH in organs was performed by grinding them in a mortar with ethanol or by combusting them in a biological oxidizer. Comparison of these extraction methods revealed that the oxidizer provides higher POH concentrations than grinding. Uptake and translocation of POH into radish seedlings occured in the first 24 hr with the highest accumulation in cotyledons. POH in cotyledons ranged from 8 to 12.4 mol g^–1 FW. Two forms of POH were found in seedlings, an ethanol-soluble one and a bound one. After 96 hr incubation, half of the recovered POH was bound in roots and hypocotyls. POH recovery in seedlings was also higher under axenic rather than non-axenic conditions. POH was degraded into ¹⁴CO₂ by microorganisms under non-sterile cultures, its concentration in culture medium decreased from 10^–3 to 10^–4 M between the first and the fourth day of incubation. Choice between sterile and non-sterile culture conditions as a method depends on particular research objectives. Non-sterile methods can be used to reflect natural processes whereas sterile methods can be used if the objective is to determine allelochemical penetration and biological effects on target plants.     

The effects of antimony and glue on zinc electrowinning from Kidd Creek electrolyte

The individual and combined effects of antimony and glue on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h zinc deposits electrowon at 500 A m^–2 and 38° C from Kidd Creek zinc electrolyte were determined. Glue increased zinc deposition polarization, reduced the deposit grain size, changed the preferred deposit orientation from basal to intermediate, but decreased the current efficiency. At concentrations above 0.02 mgl^–1, antimony had a strong depolarizing effect on zinc deposition resulting in a basal deposit orientation and very low current efficiency. Certain combinations of antimony and glue, however, optimized zinc deposition current efficiency and consistently gave an intermediate 114 112 103 102 101 preferred deposit orientation. A correlation was observed between the current efficiency (CE) and the nucleation overpotential (NOP) for zinc deposition such that the CE was a maximum when the NOP of the initial cell electrolyte was 120–130 mV and when the NOP of the final cell electrolyte was 100–110 mV.     

Combustion and the transition to detonation in a gas mixture in a closed space

The possibility of going from deflagration to detonation in mixtures of CH₄+2(O₂+N₂) and 2H₂+O₂ ±N₂ (03.76) was investigated experimentally in a space enclosed by various combinations of three thin-walled metal concentric turbulator-sphere (diameters in a ratio 124) with large numbers of openings (permeability 0.1–0.4). Transition from deflagration to detonation was observed for 1 in the first mixture and for 3.2 in the second.Balashikha. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 171–174, May–June, 1993.