Alkyl Inductive Effects on Molecular Ionization Potentials. XIV. Amides

Correlation of molecular ionization potentials, E_I, with Taft's alkyl inductive substituent constants, σ_I(R), has now been extended to include the amides. It is found that two series of amides, the formamides and acetamides, fall on two separate straight lines in accord with the general equation E_I = E_o + a_I σ_I(R), where E_o is the intercept (E_I for the parent compound), and a_I the slope. Evidence is deduced for the site of electron expulsion and a prediction is made concerning the site of vapor phase protonation of the amides.     

Functional polymers for colloidal applications. VII. Aggregate formation of lipophile-modified polyacrylates in aqueous solutions

Water-soluble copolymers, poly(dodecyl acrylate–coacrylic acid) (PDA), are synthesized by copolymerizing different ratios of dodecyl–acrylate/acrylic acid. Their aqueous solutions are transparent. The plots of I₁/I₃ (the intensity ratio of pyrene emission at 374 nm and 385 nm) and of surface tension as a function of polymer concentrations are combined to verify the existence of the aggregates of PDAs. It is found that the aggregations begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I₁/I₃ as a function of polymer concentration shows that the polymers with a higher ratio of dodecyl acrylate form polymer aggregates at lower concentrations. The hydrophobicity of the inner core of polymer aggregates is close to that of sodium dodecyl sulfate (SDS). Polymer solutions of PDA 30, PDA 30L, and PDA 15, show significant solubilization ability to pyrene. (The molar ratio of dodecyl acrylate/total acrylates is 30%, 30%, and 15% for PDA 30, PDA 30L, and PDA 15, respectively. L, low molecular weight.) The solubilization ability increases with the increase in polymer concentration and degree of substitution of dodecylamine. The intensity ratio of the excimer emission to monomer emission of pyrene (I_e/I_m) increases with increasing polymer concentration, roughly parallel to the increase in the amount of pyrene solubilized. However, the I_e/I_m at a fixed pyrene concentration (I_e/I) decreases with increasing polymer concentration. These phenomena are interpreted in terms of the amount of pyrene solubilized and the size and concentration of the polymer aggregates. © 1993 John Wiley & Sons, Inc.     

Hydration reaction and hardening of calcined clays and related minerals.: II. Influence of mineralogical properties of the raw-kaolinite on the reactivity of metakaolinite

Hydrates which form during the setting of calcium hydroxide-activated metakaolinite cements are essentially hydrated gehlenite C₂ASH₈ and CSH_I with small quantities of C₄-AH₁₃. Investigations on metakaolinite obtained by calcination of three different raw-kaolinites show that the content of CSH_I in the cement at 28 days, thus the formation rate of this hydrate, depends on the mineralogical characteristics of the raw-kaolinite (grain size, nature of impurities, and chiefly crystallization state). In another hand, for a given Water/Cement ratio, it is pointed out that the higher the CSH_I content in the material after hardening, the higher the compressive strengths.     

Coal gasification studies: Part II. Reduction in the presence of I2 with H2, and H2O + metal,at pressures up to 3500 p.s.i. and temperatures of 600°C in all quartz reactors

An experimental method is described which allows coal reduction experiments to be made in all quartz reactors at temperatures up to 600°C and pressures of 3500 p.s.i. The method is applied to the study of the reactions: Coal + H₂O + I₂ + Metal(Metal = Fe, Cr, Mo, Ni, Sn, Zn); H₂O + I₂ + Metal, and Coal + H₂ + I₂. It is shown that iodine is a catalyst for the water + metal hydrogen-producing reactions, and that the composite systems with coal are capable with Cr and Zn of completely reducing coal to gaseous hydrocarbons at 600°C. Thermodynamic and kinetic data are used to show that iodine functions as a coal reduction catalyst in the presence of molecular hydrogen at 600°C by permitting a finite steady state hydrogen atom concentration to be attained in the system.     

Functional polymers for colloidal applications. IV. Aggregate formation of lipophile-grafted water-soluble copolymers in aqueous solutions

A water-soluble styrene–maleic anydride copolymer (SMA) is derivatized with different lipophilic groups, butylamine and dodecylamine, with different degrees of substitution (5, 15, and 30%). These lipophile-grafted SMAs are water-soluble, and their solutions are transparent. A plot of I₁/I₃ as a function of polymer concentrations indicates the extent of aggregate formation. Surface tension methods also verify the existence of aggregates. It is found that the aggregates begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I₁/I₃ as a function of polymer concentrations for SMAs of different molecular weights derivatized with different lipophile with varying degrees of substitution show that the polymers with a higher degree of substitution and lower molecular weights aggregate at lower concentrations. Polymers substituted by butylamine form aggregates at a very high concentration, independent of the degree of sub-stitution. These phenomena are interpreted in terms of hydrophobic interactions as in micelles formed from surfactants. The higher degree of dodecyl-substituted SMA solubilizes pyrene at higher concentrations, and these pyrene solubilized solutions show pyrene excimer emission spectra. These emission spectra are used to characterize the relative size and hydrophobicity of aggregates. © 1993 John Wiley & Sons, Inc.     

Quantitative Analysis of Photoluminescence Quenching of Silica-Supported Molybdena Catalysts. Relation to Photocatalytic Reduction of Nitric Oxide by Carbon Monoxide

The quenching effect of NO, O₂, CO, and N₂O on the photoluminescence of Mo⁶⁺/SiO₂ has been studied at room temperature as a function of gas pressure. Nonlinear plots of the relative photoluminescence intensity I ₀/I (I ₀ is the initial intensity under vacuum) vs. pressure of the quenching gases were rationalized assuming that only adsorbed molecules efficiently quench the (Mo⁵⁺–O^-)* excited state and that the fraction of adsorbed quenching molecules can be determined from the classical Langmuir-type adsorption isotherm. The ratio of the quenching rate constants for NO and CO calculated from the computer best fits of the experimental I ₀/I–pressure dependence is in agreement with earlier data on the kinetics of the photocatalytic reduction of NO by carbon monoxide on Mo⁶⁺/SiO₂.     

Wetting of fat crystals by triglyceride oil and water. 2. adhesion to the oil/water interface

Fat crystals influence the stability of food emulsions, such as margarine, butter, or cream, if adsorbed to the oil/water interface. During the adsorption process, a new fat crystal/water interface is created, while the oil/water interface is lost. The driving force for adsorption is therefore the difference between the interactions between fat crystal/water and oil/water. In this work, we have estimated this interaction difference and compared it to the displacement energy for fat crystals from the oil/water interface to the oil. Our calculations have shown that fat crystal adsorption to the oil/water interface (expressed by contact angle ϑ) is determined by polar energy, excess of fat crystal/water over oil/water (I _sw -I _ow ). The interfacial tension constitutes the resistance force for crystal adsorption to the interface. Polar interaction energy for fat crystal/water is stronger than the polar interaction energy for oil/water in all cases examined (I _sw -I _ow >0). The difference corresponds to about 10⁴–10⁶ hydrogen bonds for a hypothetical fat crystal with a diameter of 1 μm. The displacement energy for fat crystals to oil is lower than the polar energy excess in most cases examined. Thus, an additional interaction between fat crystals and oil makes it easy to displace the crystals to the oil. There is also a relationship between the adhesion tension (-γ _ow • cos ϑ) for the crystals at the oil/water interface and the interfacial tension γ _ow . A straight line of slope -1 is achieved for systems with low interfacial tensions (γ _ow ) and low polar energy excess (I _sw -I _ow ).     

Effects of oxidation on I2 doping of trans-polyacetylene as studied via e.s.r. and conductivity measurements

Oxidation of trans-polyacetylene lowers the activation energy for conduction from 16 kcal mol^?1 to 11 kcal mol^?1 for oxidation levels of (C₂H₂O_n)_x, n = 0.144, 0.207 and 0.550. Maximum conductivity levels for 0 < x < 0.144 doped with I₂ were almost identical. At long I₂ doping times all samples exhibited some loss of conductivity. E.s.r. experiments indicate that: (1) linewidth is directly proportional to oxygen content, and (2) iodine doping is not diffusion controlled. All data are consistent with a molecular picture of PAC consisting of highly reactive localized spin states that are selectively oxidized, and less reactive delocalized states that affect conductivity more strongly via doping.     

Study on the structure of nylon 6 films iodinated before forming. II. Investigation of the crystallization behavior through thermal analysis

Two kinds of amorphous nylon 6 films iodinated before forming from the powders iodinated with 0.2N and 1.0N I₂/KI aqueous solutions were prepared by a melt‐press, and isothermally treated at 20 to 80°C for 1 day to 20 days. Thermal analyses were performed to investigate mainly the crystallization behavior on the treatment. The DSC thermograms for the treated films exhibit three temperature‐groups of endothermic peaks at 60 ～ 70°C, 105 ～ 120°C, and higher than 150°C, which may be associated with the melting of the complex crystal, the relaxed γ‐crystal, and the relaxed α‐crystal, respectively. The film containing less I₂/KI and treated at the higher temperature exhibits the peaks associated with the more stable type of crystal. The peak temperature generally increases with the treating temperature and time. On the occasion of there being two peaks associated with the γ‐crystal and the α‐crystals, ΔH for the α‐crystal increases while that for the γ‐crystal decreases with increasing the treating time. The TG curves indicate two temperature‐zones of weight loss by the volatilization of I₂ from I₅^? and the decompositions of I₃^? and nylon 6. With increasing treating temperature, the % weight loss by the volatilization of I₂ decreases, and consequently the temperature of the weight loss by the decomposition of nylon 6 increases. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1062–1069, 2004     

Further studies on cellulose III polymorphs. Transformations to cellulose IV lattices and subsequent reactions

Production of cellulose IV polymorphs, their characterization using X-ray diffraction and infrared spectroscopy, as well as the effect of chemical treatments on these polymorphs have been investigated. Cellulose III_I and III_II polymorphs, produced from celluloses I and II using EDA—MeOH treatments, were of particular interest as starting materials in the study. Celluloses IV_I and IV_II gave identical equatorial X-ray patterns in the absence of other crystal lattices in the samples. Crystallinity as well as conformation were indicated to influence production and further reactions of the samples. The latter included boiling in water, acid hydrolysis, and treatments with EDA—water, EDA—MeOH, and NaOH solutions. Cellulose IV_I → I, IV_I → I → II, and cellulose IV_II → II lattice conversions were demonstrated to occur with EDA—water treatments, thereby providing a new technique for observing these transformations. Conformational differences were apparent among celluloses I, II, III_I, and III_II, each produced using different experimental procedures.     

Synthesis and photoconductivity study of phthalocyanine polymers. I. PAA–CuPc(NO2)2

Cu–dinitro–diamino phthalocyanine was synthesized and converted to the diazonium salt. Polyacrylamide bonded CuPc(NO₂)₂ [PAA–CuPc(NO₂)₂] (I) was synthesized by hot polymerization of acrylamide and this diazonium salt. Polymer(I) is water soluble and contains about 7 mol % CuPc(NO₂)₂ rings, which are covalently bonded to PAA. Polymer(I) shows good photoconductivity, which is much better than that of the corresponding phthalocyanine monomers. By doping with iodine (I₂), the photosensitivity of polymer(I) is increased, which through fluorescence analysis is explained by the fact that a charge–transfer complex (CTC) of polymer(I) with I₂ is formed. The influence of interface layer (IFL) and charge–transportation material (CTM) on the photoconductivity of polymer(I) were also studied.     

Mathematical description of the relationship between irradiance and current flow in a photovoltaic circuit

It is demonstrated that the relationship between current flow and irradiance in a photovoltaic circuit with zero bias voltage can be simulated by the equation, I = I_m tanh (αH/I_m) + βI_mH + γI_m, where I_m is the maximum photocurrent, H is the irradiance, and α, β, and γ are constants. The total current is attributed to three components: the basal thermal or dark current (γI_m), an increase in thermal current with increasing irradiance (βI_mH), and the photocurrent (I_m tanh (αH/I_m)). The accuracy of the simulations (as measured by coefficients of determination) is greater than 99.9%. The limiting resistance of the photovoltaic cell is defined as the resistance at infinite irradiance. It is demonstrated that at infinite irradiance the total resitance of a photovoltaic circuit is the sum of the limiting resistance of the cell, the load resistance, and the equivalent resistance of the current meter. At infinite irradiance, current flow is inversely proportional to total circuit resistance.     

The influence of doping on the Raman intensity of the D band in single walled carbon nanotubes

The D band in the Raman spectra of single walled carbon nanotubes is considered as an indicator of defects in carbon nanotubes. However, its dependence on charge-transfer doping is generally ignored, despite the studied samples are often naturally doped. We studied the intensity of the D band, the ratio of the intensities of the D band and TG band (I_D/I_TG) and the ratio of the intensities of the D and G′ band (I_D/I_G′) in the Raman spectra of the single walled carbon nanotubes in dependence on a doping level. We tested two laser excitation energies viz 2.41 and 1.92 eV, which are in resonance with semiconducting and metallic tubes, respectively in our sample. It is shown that the D band intensity is significantly attenuated in doped carbon nanotubes sample for both semiconducting and metallic tubes. The I_D/I_TG ratio is weakly dependent on doping for semiconducting tubes but for metallic tubes the I_D/I_TG ratio exhibits strong dependence on doping. The I_D/I_G′ ratio is suggested for evaluation of the defects in carbon nanotubes samples since it is less sensitive to doping both for semiconducting and metallic tubes. Nevertheless, for highly doped samples even the I_D/I_G′ ratio exhibits significant dependence on doping level.     

Ideality of pressure‐sensitive paint. I. Platinum tetra(pentafluorophenyl)porphine in fluoroacrylic polymer

The pressure sensitive paint (PSP) properties of a fluoroacrylic polymer, FIB, with the luminophor platinum tetra(pentafluorophenyl)porphine (PtTFPP) are presented. This paint forms a hard coating that displays Stern–Volmer plots with a high dynamic range (∼ 0.9) [defined as (I_vac − I_atm)/I_vac], good photostability, a response time of less than 1 s and a relatively low temperature dependence (∼ 0.6% per degree). The temperature dependence is low because FIB has a unusually low activation energy for the diffusion of oxygen. Pressure and temperature affect intensity independently making this PSP “ideal.” The basecoat affects the functionality of the PSP it underlies, and the optimal basecoat used to date also includes the FIB polymer. The synthesis of the FIB polymer is a copolymerization that occurs in one step with a peroxide initiator. Annealing the painted model above T_g = 70°C procures adhesion and ideality. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2795–2804, 2000     

Fracture toughness of adhesive joints. II. Temperature and rate dependencies of mode I fracture toughness and adhesive tensile strength

It has been known that adhesive strength shows temperature and rate dependencies reflecting visoelastic properties of an adhesive. Similarly, a critical strain energy release rate is expected to show temperature and time dependencies deformation and fracture of the adhesive occurs at the time of measurement of the critical strain energy release rate, which is a kind of fracture mechanical parameter for adhesive joints. The term “critical strain energy release rate” has usually been called “fracture toughness.” In this study, the critical strain energy release rate (G_IC) of the opening mode was called mode I fracture toughness. G_IC was measured over a wide range of temperatures and rates, and then a master curve was obtained by applying the temperature–rate superposition principle to the obtained data. Also, on the relation between G_IC and adhesive tensile strength is discussed. © 1995 John Wiley & Sons, Inc.     

Diffusion of dyes in polyester fibers. IV. Anomalous sorption of disperse dye synthene scarlet P3GL

The investigations on dyeing of poly(ethylene terephthalate) fibers with disperse dye Synthene Scarlet P3GL have revealed anomalous sorption of the dye in heat-treated samples. In the mathematical solution of the process it has been assumed that anomalous sorption can be treated as superposition in time of two stages of Fickian sorption. The contents of absorbed dye at quasiequilibrium C_I, at the final equilibrium C_II, and the apparent diffusion coefficients D_I, and D_II have been calculated using Hill's equation.     

Oil Content and Composition of Sesame (Sesamum indicum L.) Genotypes as Affected by Irrigation Regimes

The fatty acid composition of sesame seed oil determines its commercial value, and drought stress and genotype may affect both the quality and quantity of oil that is extractable by sesame seed processors. Therefore, this experiment was conducted in a field located in Isfahan, Iran, to determine the effect of three irrigation regimes [55 % (I ₁, as control), 75 % (I ₂) and 85 % (I ₃) of depletion of soil available water] on the oil content and composition of ten sesame genotypes (Isfahan4, Shahreza, Borazjan, Ahvaz, Kal, Shiraz, Markazi, Ardestan, Ultan and Isfahan1). Seed oil content and palmitic, linoleic, linolenic, stearic and oleic acid contents were determined during 2010–2012. Shahreza under I ₁, Shahreza and Ardestan under I ₂ and Isfanahan4 under I ₃ irrigation regimes produced the highest oil content, while Kal under I ₁ and I ₂ and Isfahan4 under I ₃ irrigation regimes produced the highest oil yield. Ultan had the lowest palmitic acid content under all three irrigation regimes, while Isfahan4 had the highest reduction in palmitic acid content under I ₂ and I ₃. Borazjan produced the lowest stearic and highest linoleic acid contents under the I ₁, I ₂ and I ₃ irrigation regimes. Kal, Kal and Ardestan, and Ardestan and Isfahan1 produced the highest oleic acid under I ₁, I ₂ and I ₃, respectively. Shahreza under I ₁ and I ₂ and Isfahan4 under I ₃ had the highest linolenic acid content. The results showed that the sesame oil content and composition were genotype-drought level specific, and based on oil yield production and percent reduction in saturated and increase in unsaturated fatty acid contents, Isfahan4 was the most drought-tolerant genotype.     

Influences of carbon structure on the reactivities of lignite char reacting with CO2 and NO

Raw and demineralized lignite samples were pyrolyzed from 773 to 1673 K to generate chars. The chars were characterized with Raman spectroscopy for the structure evolution. The reactivities of the chars reacting with CO₂ and NO were measured with thermogravimetric analysis. The derived reactivity indexes were correlated with the treatment temperature and the Raman structural parameters to demonstrate the applicability of Raman spectroscopy for evaluation of the reactivities of char CO₂ gasification and char-NO reaction. It was found that char microstructure evolution with the treatment temperature could be represented by Raman band area ratios. I_D1/I_G and I_G/I_ALL represented the evolution of the ordered carbon structure while the combination of I_D3/(I_G + I_D2 + I_D3) reflected the evolution of the amorphous carbon structure of the lignite chars with increasing the treatment temperature from 773 to 1673 K. Reactivity indexes of the demineralized chars reacting with both CO₂ and NO were found to increase with increasing the treatment temperature, implying that the structure ordering did result in the losses of the reactivities. Higher reactivities of the non-demineralized chars indicated the catalytic role of inorganic matter in the reactions with both gases. I_D1/I_G and I_G/I_ALL had good linear correlations with the reactivities particularly of the demineralized chars if considering the structure evolution behaviors at lower and higher temperatures, respectively. I_D3/(I_G + I_D2 + I_D3) was found to have fairly good linear correlations with the reactivity indexes of the lignite chars generated over the whole temperature range.     

Interaction of Turkish Beypazari lignite with I2

Samples of original and acid-washed Beypazari lignite were treated with I₂ and the effects of the I₂ treatment on the coal structure was investigated. It was found that I₂ attachment to the coal structure obeyed Langmuir-type of adsorption model. Treatment of coals with I₂ produced new iodine chemical compounds and the emergence of newly created chemical iodine structures was followed with the FTIR spectra. I₂ treatment also created charge transfer complexes. Increase in the free radical concentrations of the I₂-treated coals was due to the formation of charge transfer complexes between I₂ and aromatic systems in the coal by single electron extraction from the donor to the I₂. The splitting of aromatic stretching vibrations in the FTIR spectra of I₂-treated coals towards lower wavelengths also indicated the creation of charge transfer complexes in the coals after I₂ treatment where the I₂ acted as the electron acceptor.