Synthesis of copolyimide containing fluorine and naphthalene with synergizing effect on dielectric constants

Summary Novel copolyimides containing fluorine and naphthalene groups were synthesized from 4,4-(Hexafluoroisopropylidene)diphthalic dianhydride (6FDA) and two diamines, 1,4-Bis(4-amino-2-trifluoromethylphenoxy) benzene (BATB) and 2,7-bis(4-aminophenoxy) naphthalene (BAPN) in various ratios via thermal imidization. The introduction of fluorinated groups into dianhydride improved transparency of copolyimides. All films are transparent. The structures and physical properties of copolyimides were characterized by FT-IR, DSC, TGA, XRD, UV-Vis and dielectric analyzer to study the effect of diamines on the physical properties of modified polymers. Copolyimides containing a higher percentage of BAPN have higher glass transition temperature and are less soluble in organic solvents. The copolyimide consisting of 50/50 mole% of BATB/BAPN has the lowest dielectric constant (2.60 at 1 KHz), reflecting the synergizing effect from both diamines.     

Response of two okra (Abelmoschus esculentus L. Moench) varieties to fertilizers: Yield and yield components as influenced by nitrogen and phosphorus application

The response of two okra (Abelmoschus esculentus L. Moench) varieties (White velvet and NHAE 47-4) to fertilization in northern Nigeria was examined using four rates of nitrogen (0, 25, 50 and 100 kg ha^–1) and three rates of phosphorus (0, 13 and 26 kg ha^–1). Nitrogen application significantly increased green pod yield, pod diameter, number of fruits per plant, number of seeds per pod and pod weight. Application of phosphorus also significantly increased green pod yield, pod number and number of seeds per pod. The two varieties responded to nitrogen application differentially with respect to green pod yield. For optimum green pod yield of White velvet 35 kg N ha^–1 is suggested while for variety NHAE 47-4, N fertilization can be increased to 70 kg ha^–1. There was no differential response of varieties to phosphorus fertilization for green pod yield; however, the application of 13 kg ha^–1 enhanced the performance of both varieties.     

Synthesis and Properties of Novel Soluble and Thermally Stable Optically Active Poly(amide-imide)s from N,N’-(4,4’-Oxydiphthaloyl)-bis-L-phenylalanine Diacid Chloride and Aromatic Diamines

Summary In this research work, 4,4-oxydiphthalic anhydride (1) was reacted with L-phenylalanine (2) in acetic acid and the resulting imide-acid 3 was obtained in high yield. This imide-acid 3 was converted to diacid chloride 4 by reaction with thionyl chloride. The polycondensation reaction of diacid chloride 4 with several aromatic diamines such as 4,4-sulfonyldianiline (5a), 4,4-diaminodiphenyl methane (5b), 4,4-diaminodiphenylether (5c), p-phenylenediamine (5d), m-phenylenediamine (5e), and 4,4-diaminobiphenyl (5f) was performed by two conventional methods: low temperature solution polycondensation and short period reflux conditions. Several new thermally stable optically active poly(amide-imide)s with inherent viscosity ranging from 0.34–0.62 dL/g were obtained with high yield. All of the above polymers were fully characterized by ¹H-NMR, FT-IR, elemental analyses and specific rotation techniques. Some structural characterizations and physical properties of this new optically active poly (amide-imide)s are reported.     

Synthesis of α,ω-bis(2,6-dimethylphenol)-poly(2,6-dimethyl-1,4-phenylene oxide) by phase transfer catalyzed polymerization of 4-bromo-2,6-dimethylphenol in the presence of 2,2-di(4-hydroxy-3,5-dimethylphenyl)propane

Summary ,-Bis(2,6-dimethylphenol)-poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-2OH) was synthesized by the radical-cation phase transfer catalyzed polymerization of 4-bromo-2,6-dimethylphenol (1) in the presence of 2,2-di(4-hydroxy-3,5-dimethylphenyl)propane (2). Copolymerization experiments were performed by a liquid-liquid two phase, benzene/1.5 N NaOH (aq), phase transfer catalyzed reaction with tetrabutylammonium hydrogen sulfate (TBAH) or tricaprylmethyllammonium chloride (Aliquat 336) catalysts. A series of copolymerization experiments were performed with 1/2 molar ratios of 4/1, resulting in PPO-2OH with M_n in the range of 2200–3200 g/mol. Phase transfer catalyzed etherification of the PPO-2OH chain ends with p-chloromethylstyrene was used to synthesize ,-bis(vinylbenzyl ether)s of the PPO-2OH (PPO-2VBE). The chain microstructure and the fuctionality of both PPO-2OH and PPO-2VBE was studied by 200 MHz ¹H-NMR spectroscopy.     

A miscibility study of ternary blends of polystyrene,tetramethylbisphenol-A polycarbonate,and poly(2,6-dimethyl-1,4-phenylene oxide)

Phase behaviorof ternary blends of polystyrene (PS), tetramethylbisphenol-A polycarbonate (TMPC), and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at two different temperatures (i.e., 210 and 300 °C, respectively) was studied by means of differential scanning calorimetry. Miscibility of the ternary blends at either temperature was found restricted to limited compositions, in agreement with simulated spinodal curves based on published values of interaction parameters. The limited ability of PS, which is separately miscible with TMPC and PPO at 210 °C, to act as a common solvent for the immiscible TMPC/PPO pair at this temperature was explained in terms of the disparity in PS/TMPC and PS/PPO pair interactions (i.e., the 'X effect).     

Phosphorus (P) management in the ‘De Marke’ dairy farming system

In the sandy regions of the Netherlands water quality is threatened by high losses of nutrients from intensive dairy farms. About 67% (32 kg ha^-1yr^-1) of farm inputs of P in purchased feeds and fertilisers do not leave in milk or cattle. The Dutch government defined decreasing maximum permitted nutrient surplusses for the period 1998–2008, at 9 kg ha^-1yr^-1 for P. Farmers suppose that reducing the surplusses will be costly, because it limits application of slurry, which then has to be either exported or additional land has to be purchased. Moreover, farmers are worried about the impact on soil fertility and crop growth. To explore the possibilities of reducing surplusses by improved management, farming systems research is carried out at prototype farm De Marke. Results indicate that average intensive dairy farms can reduce P surplus sufficiently, without the need to buy land or to export slurry. Key factors are reductions in purchased feeds (by reduced needs per kg milk as a result of a higher milk yield per cow, less young stock and judicious feeding) and fertilisers (by improved management of home-made manure and an increased maize area). Initially, P fertility status of the fields of De Marke decreased, but stabilised in the seventh year at a level not restrictive to crop production.     

Studies on the response of ‘Tifblue’ and ‘Woodard’ rabbiteye blueberries to fertilizers

A field study was conducted to investigate the effects of three fertilizer placement methods and 11 fertilizer formulations on plant survival, economics of replanting, yield, and fruit size of two rabbiteye blueberry (Vaccinium ashei Reade) cultivars Tifblue and Woodard. Fertilizer rates were either mixed with the soil under plants (before planting), sidedressed, or half-rate was placed under plants with the other half sidedressed. Fertilizers at planting caused a total of 34% Woodard and 12% Tifblue plants to die as compared to 6% for Woodard and none for Tifblue when no fertilizer was applied. Fertilizer formulas 2-1-1 and 5-10-10 oxide ratios placed under Woodard plants caused 100% mortality whereas Tifblue fertilized with oxide ratios 2-2-2 and 5-10-10 under plants reached the maximum 50% mortality. Splitting fertilizer placement under the side of the plants resulted in less Woodard plant mortality (30%) than placing all the fertilizer under plants (54%). However, plant mortality for the side/under group was not different than sidedressing all fertilizer (23%). A planted hectare in this experiment consisted of 1852 Tifblue and 926 Woodard plants, providing one Woodard plant to pollinate two Tifblue plants. Based on the results obtained, the 5-10-10 fertilizer placed under plants would be expected to cause half the Tifblue (926 plants) and all the Woodard (926 plants) to be replanted. Plant costs alone was estimated to be $2315 with additional replanting costs of $93 for Tifblue and much higher for Woodard. Sidedressing 5-10-10 fertilizer eight weeks after planting would have prevented plant mortality. Placement of various fertilizers under Woodard or Tifblue plants resulted in a significant increase in plant mortality as compared to side placement of fertilizers. Yield loss due to plant mortality increased linearly with the N level of the fertilizers (ranging from 0 to 2) for both cultivars. Woodard fruit size was not affected by fertilizer placement but placing fertilizers under Tifblue plants produced smaller yields with larger fruit than sidedressed plants. Blueberry plants in a virgin acidic soil may experience no reduction in yield if fertilization is completely eliminated.     

Electrochemistry of anodic F2 evolution at carbon electrodes: Bubble adherence effects in the kinetics at rotating cone electrodes

Fluorine-evolving carbon anodes exhibit unusually high overvoltages characterized also by remarkably large Tafel slopes having values 0.4–0.8 V per decade of current density change. Also, at high current densities, a so-called anode effect associated with a type of passivation sets in. Experiments are described which aim to distinguish high polarization arising from an intrinsically large Tafel slope, generated by a non-ohmic charge transfer barrier layer effect due to CF film formation, from effects due to difficulties of F₂ bubble detechment and F₂ gas film formation at the CF film. Steady state polarization measurements have been made at a rotating carbon cone electrode from which F₂ bubbles, which otherwise remain attached to the electrode and block access to the electrolyte, can be spun away. At the rotated electrode, at low and intermediate current densities, linear Tafel behaviour is still observed but with high slopes associated with the barrier layer film effect. At higher current densities an anode effect, associated with the F₂ gas film, is developed, leading to a type of passivation of the electrode. The two sources of unusually high polarization in the F₂ evolution reaction at carbon are not independent as it is also the formation of the CF film that causes difficulties in gas bubble detachment owing to the lyophobic properties of the fluorinated C/F₂/KF·2HF interface. Polishing effects confirm this conclusion.     

Effect of amounts and sequence of additions of urea and water on hydrolysis of surface-applied granular urea in unsaturated soils

The hydrolysis of surface-applied granular urea ( 15 mg of urea/particle) in 14 unsaturated soils as influenced by the amounts and the sequence of additions of urea and water and studied using open and covered soil column systems was in the following order: well-mixed surface-applied surface-applied surface-applied urea, granular urea, granular urea, granular urea, water added > water added > water added water added before, after, before, before, no drying no drying no drying drying The retarded hydrolysis' of surface-applied granular urea is attributed to retarded soil urease activity. Under the nondrying and drying conditions, the positive effect of increasing amounts of added water on the hydrolysis was less apparent when water was added 24–48 hours before than when it was added immediately after surface application of granular urea. When an increasing number of urea granules were evenly placed on a finite surface of unsaturated soil, the rate of urea application (quantity factor) increased but the percentage of urea hydrolyzed remained practically unchanged. These results suggest that it is necessary to consider effective urea concentration and effective urease activity for adequate understanding of in situ hydrolysis of broadcast fertilizer urea in unsaturated soil.     

Cathodic behaviour of IrO2 electrodes in alkaline solution Part I: Electrochemical surface characterization

IrO₂ electrodes prepared by thermal decomposition of IrCl₃ on a titanium support at temperatures of calcination between 300 and 500°C have been characterized by cyclic voltammetry and potential steps. Standard voltammetric curves have been recorded between –0.65 and 0.35 V vs SCE (prior to H₂ and O₂ evolution) as a fingerprint of the surface state, and the associated charge,q ^*, has been used to monitor the morphology of the active layer. The effect of hydrogen evolution has been investigated by progressively decreasing the negative potential limit, and by increasingly holding the electrode under hydrogen evolution at a constant potential. Phenomena of proton penetration beneath the outer surface into an inner surface have been quantified by potential step experiments. The effect of storing the electrodes in water rather than in the open air has also been investigated. The thermal oxides lose their typical features at calcination temperature < 350° C. Cathodic load does not appear to cause macroscopic modifications of the surface state.This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday, and in recognition of his outstanding contribution to electrochemistry.     

Assessment of the relative agronomic effectiveness of phosphate rocks under glasshouse conditions

Six phosphate rocks (PRs) of varying reactivities were compared with monocalcium phosphate (MCP) in a glasshouse experiment growing perennial ryegrass (Lolium perenne cv. Nui) as the test plant on four soils of contrasting P sorption capacity and exchangeable Ca. The cumulative dry matter yield over 10 harvests showed a significant response to P application in all soils. Based on relative yield and P uptake, MCP was the most effective P fertilizer followed by the reactive phosphate rocks, which were superior to the unreactive rocks in all soils. The relative agronomic effectiveness (RAE) and substitution ratio (SR) of individual PR fertilizers, calculated with respect to MCP using the methods of vertical and horizontal comparison, respectively, were similar over a range of fertilizer rate. There was a decline or slight increase in the performance of PRs with time in the low P sorption soils but a consistent increase in the high P sorption soils. Some initial influence of exchangeable Ca content of the soils on the relative performance of PRs was also observed. Generally the PRs performed better in high P sorption soils than low P sorption soils and in low exchangeable Ca soils than high exchangeable Ca soils.     

Chemical modification of copoly(methylsilylene/1,4-phenylene) by Pt-catalyzed hydrosilation reactions with functionally substituted alkenes

Copoly(methyl-3-biphenoxypropylsilylene 1,4-phenylene), copoly(methyl-3-cyanopropylsilylene 1,4-phenylene), copoly(methyl-3-ethoxypropylsilylene 1,4-phenylene), copoly(methyl-3-phenoxypropylsilylene 1,4-phenylene), and copoly(methyl-4,7,10,13-tetraoxatetradecanylsilylene 1,4-phenylene) have been prepared by platinum-catalyzed hydrosilation graft reactions between poly (methylsilylene 1,4-phenylene) and appropriate functionally substituted alkenes. These polymers have been characterized by¹H,¹³C, and²⁹Si NMR as well as by FT-IR and UV-vis spectroscopy. The molecular weight distribution of these polymers has been determined by gel permeation chromatography (GPC), and their glass transition temperatures (T _e) by DSC.     

Two-variable periodic perturbation of kinetic oscillations

Using one of the generic models (CO oxidation on Pt with surface-oxide formation) predicting kinetic oscillations in heterogeneous catalytic reactions, we show that the efficiency of two-variable periodic perturbations with respect to converting natural period-1 oscillations to period-l oscillations at the forcing frequency is remarkably sensitive to the kind of perturbations used. Counter-phase perturbations are much more effective compared to in-phase perturbations. The physics underlying these findings is suggestive of their applicability to many other models and/or real systems exhibiting kinetic oscillations.     

Synthesis of pH Sensitive Organic-Inorganic Polymer Hybrids

Summary The synthesis of pH sensitive organic-inorganic polymer hybrids from poly(2-hydroxyethyl methacrylate) derivatives and alkoxysilane is described. To a reaction mixture of poly(2-hydroxyethyl methacrylate) derivatives, tetramethoxysilane, 2,7-bis(carboxyethyl)-4- or 5-carboxyfluorescein (BCECF) as a fluorescent probe, and ten equivalents of HCl aqueous solution in methyl ethyl ketone / propanol (7/3, v/v) were added. The resulting mixture was kept stirring at room temperature for 1 h and was heated at 40 °C for 2 weeks. The changes of the pH were estimated as changes in the fluorescence intensity with the pH sensitive fluorescence probe BCECF trapped within the obtained polymer hybrid. Consequently, the pH value was found to be proportionate to the fluorescence intensity.     

Effect of the naturally occurring salt ‘Kanwa’ as a fertilizer on the productivity ofStylosanthes in the subhumid zone of Nigeria

Soil nutrient deficiencies pose a serious limitation to higher crop and forage yields in the Nigerian subhumid zone. Some of the deficiencies may be alleviated by using as a fertilizer a salt mined locally called Kanwa which is traditionally used as a cattle lick. Yields ofStylosanthes hamata cv Verano andS. guianensis cv Cook seed and dry matter increased with Kanwa application at different locations. The effect of Kanwa was enhanced when phosphorus was adequately supplied. Improvements to soil physical properties were proportional to the yield of the legume. The implications of good quality fodder and improved soil conditions in Agro-pastoral Systems in the Nigerian SHZ are discussed.     

Chemical effects in commercial and laboratory mixtures of ‘reactive’ phosphate rock and acidulated fertilisers

The chemical analyses of different size fractions of a variety of commerical and laboratory prepared samples of partially acidulated phophate rocks and mixtures of reactive phosphate rock and single superphosphate (called LONGLIFE in New Zealand) have been studied. Whereas only minor chemical segregation effects have been observed for partially acidulated products quite a large bias has been established for LONGLIFE materials, and more especially commercial samples, where larger proportions of phosphate rock were found in the lower size fractions. This inhomogeneity was considered to arise from poor mixing of components and subsequent inconsistent granulation; more stringent rejection criteria for undersize material would greatly assist in improving the product quality. Chemical deactivation of the phosphate rock residue in LONGLIFE materials was also observed; this can be partially explained by a selective reaction of the reactive phosphate rock component with acid still present at the time of mixing with the single superphosphate component.     

Synthesis and characterization of 4,4’–(dimethylsilylene) bis( phenyl chloroformate) and 4,4’–(dimethylgermylene)bis(phenyl chloroformate) and their use in the synthesis of poly(urethanes)

Summary The synthesis of 4,4–(dimethylsilylene)bis(phenyl chloroformate) and 4,4–(dimethylgermylene)bis(phenyl chloroformate) is described according to the same route for the synthesis of bisphenol–A bischloroformate. These compounds were characterized using elemental analysis, FT–IR and NMR spectroscopy. Poly(urethanes) derived from these bischlororformates containing silicon or germane in the main chain, were obtained in benzene solution by reaction with 4,4–methylenedianiline in the presence of pyridine. Poly(urethanes) were characterised by spectroscopic methods and the thermal properties (Tg and thermal stability) were compared with the homologue poly(urethane) obtained from bisphenol–A chloroformate.     

Carriers of molecular oxygen on the basis of metal complexes incorporated in polyorganosiloxane matrices

Using sol-gel technology, samples of poly[3-(2-imidazolin-1-yl)propyl]siloxane matrices containing incorporated complexes of Co(II) withN. N-bis(salicylaldehyde)ethylenediamine andN. N-bis(salicylaldehyde)o-phenylenediamine were obtained. EPR investigations of the matrix-trapped compounds demonstrated that most of the cobalt atoms belong to high-spin tetrahedral complexes and a small fraction of them is in a low-spin oxygen complex.     

The influence of side-chain and main-chain spacer lengths on the thermal and structural properties of diethanolamine based side-chain polyesters

Summary A series of linear side-chain aliphatic polyesters have been synthesized from -(bis(2-hydroxyethyl)amino)--(4-methoxybiphenyl-4-oxy) alkanes and aliphatic acid chlorides. The side-chain and main-chain spacer lengths were varied and their influences on thermal and structural properties of polyesters, as determined by DSC and X-ray diffraction, are discussed.     

Electrochemistry of anodic fluorine gas evolution at carbon electrodes: Part II studies on the ‘CF’ film by the current-interruption,AC impedance,ESCA and auger techniques

The CF films that are formed on the surface of carbon anodes used for the fluorine evolution reaction (FER) in KF·2HF melts at 358 K have been studied by bothin situ electrochemical current-interruption and a.c. impedance methods, and byex situ surface spectroscopy [ESCA (XPS) and Auger] techniques. The surface analysis measurements indicate that a thin CF (CF₂) film, 1.7 nm in thickness is formed on the carbon anodesurface. Results from depth profiling analyses of the film indicate that it is not uniform, higher levels of CF and F components being found towards the carbon anode surface. Thein situ electrochemical measurements demonstrate that an abnormally small interfacial capacitance, (1.6–2.7)×10^–7 F cm^–2, arises in the course of the FER at carbon anodes; this was attributed to the presence of a passive dielectric CF film on the carbon electrodes. The determined interfacial capacitance does not change significantly with potential in the potential range studied, which implies that the thickness of the CF film on the fluorine-evolving carbon anodes may be independent of potential.