Studies on Cellulose Acetate Phthalate. 3. Osmotic Pressure Measurements

Osmotic pressure measurements of aqueous solutions of cellulose acetate phthalate (CAP) were carried out with the help of a highspeed membrane osmometer. The value of the osmotic coefficient, g, for different concentrations of CAP, as well as at different degree of neutralization for various concentrations, were estimated. The effect of concentration and degree of neutralization on the value of g were investigated. The experimental results were also treated in the light of Oosawa' theory.     

Thermal decomposition of ethanol. 4. Ab initio chemical kinetics for reactions of H atoms with CH3CH2O and CH3CHOH radicals

The potential energy surfaces of H-atom reactions with CH(3)CH(2)O and CH(3)CHOH, two major radicals in the decomposition and oxidation of ethanol, have been studied at the CCSD(T)/6-311+G(3df,2p) level of theory with geometric optimization carried out at the BH&HLYP/6-311+G(3df,2p) level. The direct hydrogen abstraction channels and the indirect association/decomposition channels from the chemically activated ethanol molecule have been considered for both reactions. The rate constants for both reactions have been calculated at 100-3000 K and 10(-4) Torr to 10(3) atm Ar pressure by microcanonical VTST/RRKM theory with master equation solution for all accessible product channels. The results show that the major product channel of the CH(3)CH(2)O + H reaction is CH(3) + CH(2)OH under atmospheric pressure conditions. Only at high pressure and low temperature, the rate constant for CH(3)CH(2)OH formation by collisonal deactivation becomes dominant. For CH(3)CHOH + H, there are three major product channels; at high temperatures, CH(3)+CH(2)OH production predominates at low pressures (P < 100 Torr), while the formation of CH(3)CH(2)OH by collisional deactivation becomes competitive at high pressures and low temperatures (T < 500 K). At high temperatures, the direct hydrogen abstraction reaction producing CH(2)CHOH + H(2) becomes dominant. Rate constants for all accessible product channels in both systems have been predicted and tabulated for modeling applications. The predicted value for CH(3)CHOH + H at 295 K and 1 Torr pressure agrees closely with available experimental data. For practical modeling applications, the rate constants for the thermal unimolecular decomposition of ethanol giving key accessible products have been predicted; those for the two major product channels taking place by dehydration and C-C breaking agree closely with available literature data.     

Pressure dependence of dielectric properties of chlorinated polyethylene vulcanizate. I. α relaxation and shift factors

The complex dielectric constant was measured under elevated pressure for the α relaxation of vulcanized chlorinated polyethylene. Both temperature and pressure effects on the static dielectric constants, the activation enthalpy, and volume, and the pressure dependence of the glass-transition temperature were obtained. The dependence of shift factors on temperature was expressed by the Vogel–Fulcher–Tamman–Hesse (VFTH) equation: ?log a_T = A ? B/(T ? T₀). The parameters A, B, and T₀ for each pressure applied were calculated by minimizing the standard deviation between log a_T and experiments. The values of the parameters in the Williams–Landel–Ferry (WLF) equation: ?log a_T = C₁(T ? T_g)/[C₂ + (T ? T_g)], were also estimated from the resulting values of the VFTH parameters. All these parameters depended on pressure. The activation volume plotted against T ? T_g decreased with increasing pressure.     

Infrared spectroscopic analyses of transformations of chemical species on the silica highly-reacted with gaseous BF3.

Transformations of chemical species formed by the reaction of gaseous BF3 with high pressure and silica preheated at 473 and 1093 K were studied with the use of infrared absorption spectrometry. The species containing -BF2 and the species containing >BF were transformed to each other on the highly-reacted silica depending on the pressure of BF3 in cell, and some of the species containing -BF2 were also desorbed without their transformations to the species containing >BF. H2O played important roles in these transformations.     

Interaction forces in thin liquid films stabilized by hydrophobically modified inulin polymeric surfactant. 3. Influence of electrolyte type on emulsion films

The interaction forces in emulsion films stabilized using hydrophobically modified inulin (INUTEC SP1) were investigated as a function of concentrations of electrolytes of different types (NaCl, Na2SO4, and MgSO4). At a constant disjoining pressure of 36 kPa, a constant temperature of 22 degrees C, and a film radius of 100 microm, the film thickness, hw, decreased with an increase in electrolyte concentration until a critical value, Cel,cr, was reached above which hw remained constant. Cel,cr decreased with an increase in electrolyte valency (Cel,cr = 5 x 10(-2) mol.dm(-3) for NaCl and 1 x 10(-2) mol.dm(-3) for Na2SO4 and MgSO4). The reduction in film thickness below Cel,cr could be accounted for by the compression of the electrical double layer. The Pi-hw isotherms below Cel,cr could be fitted using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (constant charge and constant potential cases were considered). At a certain pressure, the film jumped to a Newton black film. The pressure at the jump decreased with an increase in electrolyte valency as a result of the reduction of the electrostatic barrier. At electrolyte (NaCl, Na2SO4, or MgSO4) concentrations higher than Cel,cr, the jump occurred at a low pressure that was independent of the electrolyte type. The thickness of the Newton black film was independent of both the concentration and nature of the electrolytes studied. The results show clearly that the polyfructose loops and tails remain strongly hydrated both in water and in high concentrations of electrolytes of different types, and these results explain the high INUTEC SP1 emulsion stability against coalescence of emulsions prepared under such conditions.     

Surface grafting of polyethylene by mutual irradiation in methyl acrylate vapor. I. γ irradiation

Mutual irradiation of polyethylene (PE) in methyl acrylate vapor easily forms a poly(methyl acrylate) (PMA) homopolymer layer on the inner graft copolymer layer consisting of both PE and PMA components as a result of the rapidly increasing surface-graft composition. This growth process of surface grafting has been found to provide some specific kinetic features different from those in other surface-grafting systems. With formation of the surface homopolymer layer, low- and highdensity PE sheets give the same grafting rate, whereas both sheets give different rates in grafting stages or conditions in which the homopolymer layer is not formed. This result indicates that most monomers, penetrating across the surface, are entrapped or consumed in the surface homopolymer layer; accordingly the rate becomes independent of the type of PE sheets that have significantly different diffusion coefficients. The thickness of the inner graft copolymer layer, which is kept constant after homopolymer-layer formation, increases with decreasing dose rate and with increasing monomer vapor pressure and temperature. This behavior can be qualitatively explained according to an equation for the initial steady-state grafting depth.     

Critical loci for binary chloroalkane-n-alkane mixtures. II. Dichloromethane with C3-C9 n-alkanes

Gas-liquid critical temperature and pressure were determined experimentally at several compositions for the seven binary mixtures formed by dichloromethane with propane through n-nonane. The results are presented on the P–T, T–x and P–x planes which reveal a regular pattern of behaviour as the size of the n-alkane varies.     

Polymerization in the crystalline state. VIII. Polymerization in N-carboxy anhydrides of γ-benzyl glutamate, γ-methyl glutamate,and ϵ-carbobenzoxylysine

The kinetics of the solid-state polymerization of the N-carboxy anhydrides (NCA) of the L - and racemic forms of γ-benzyl glutamate (BG), γ-methyl glutamate (MG), and ?-carbobenzoxylysine (CL) were studied as a function of temperature and aqueous vapor pressure. The reaction of the L -forms of BG and MG was characterized by an induction period, while the CL derivative reached its maximum polymerization rate at the outset of the reaction. Water vapor had only a minor effect in accelerating the reaction and reducing the chain length of the polypeptides formed. The racemic monomers were found to have different crystal structures from those of the L -isomers and the racemic MG and CL derivatives polymerized much more slowly than the corresponding optically active crystals. All polymers gave diffuse x-ray diffraction patterns. Infrared spectra of the L -polypeptides showed that they were largely in the α-helical form. The polymer derived from the racemic BG–NCA had a content of α-helical material which suggested that it consisted of polypeptides with long blocks of D and L residues.     

Neutron scattering experiments on fully deuterated liquid N-methylformamide DCONDCD3 at various temperatures and under pressure. Comparison to X-ray results

Neutron scattering experiments are performed on fully deuterated liquid N-methylformamide (C2D5NO) at various temperatures and under pressure. The recorded data at atmospheric pressure and room temperature are analyzed to yield the molecular form factor and the distinct pair correlation function. Our measurements clearly show that the hydrogen-bond network, of which the parameters are deduced, persists locally in the liquid. The experimental structure factor could be explained in terms of short-range crystal structure. The r(N...O) distance decreases with increasing temperature from 293 to 398 K, whereas no significant variation of the intermolecular structure is detected when varying pressure from 1 bar to 4 kbar. Along the study, some comparison is made with complementary X-ray results.     

Der PuBr3-Typ als Hochdruckmodifikation bei Seltenerd-Trihalogeniden LnX3 (X = Cl,Br, I)

PuBr₃ Type as High Pressure Modification of Rare Earth Trihalides LnX₃ (X = Cl, Br, I) High pressure experiments in a belt-type apparatus were performed on rare earth trichlorides, -bromides and -iodides. The results underline the importance of the PuBr₃-type arrangement. The range of existence of this structure type is considerably increased under pressure. X-ray high temperature investigations at ambient pressure on the quenched high pressure phases show a marked correlation between the transformation pressures, which rise with smaller cations, and the temperatures at which the high pressure phases are reconverted to the thermodynamically stable ones.     

Reaction of the superacid HGeCl3 with aromatic compounds. 5. Hydrogermylation of benzene,toluene, m-xylene,and mesitylene at high pressure

Conclusion Trichlorogermane under pressure can effect the noncatalytic hydrogermylation of aromatic multiple bonds in benzene and its simpler methyl derivatives with the preferential formation of the corresponding bisgermyl derivatives of cyclohexene. The reaction is accelerated by the introduction of methyl groups into the molecule in agreement with the electrophilic nature of trichlorogermane, and the considerable accelerating effect of high pressure can be considered as evidence of a slow stage in this process, proceeding via a molecular mechanism.For communication 4, see [1].For the preliminary communication, see [2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 882–886, April, 1987.The authors wish to thank M. Ya. Botnikov for assistance in carrying out the GLC-mass spectrometry studies.     

Reactions of antioxidants with molecular oxygen. Part II. Isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate in silicone matrix

The study of oxidation kinetics of isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1135) stabiliser was carried out using silicone oil as an inert substrate. The stabiliser was exposed at 80-120 °C under 0.02-3.0 MPa oxygen pressure. UV/VIS spectrophotometry, gel permeation chromatography and high pressure liquid chromatography were used to follow the stabiliser consumption, whose kinetic parameters were determined by applying a simple kinetic model.     

ChemInform Abstract: High Pressure Superconducting Phase of BI3: An ab initio Study.

The high pressure crystal structure of BI₃ with space group P2₁/c consisting of B₂I₆ dimers is determined using an ab initio evolutionary algorithm for crystal structure prediction in conjunction with density functional theory.     

Electron attachment to POCl3. III. Measurement and kinetic modeling of branching fractions

Electron attachment to POCl(3) was studied in the bath gas He over the pressure range 0.4-3.1 Torr and the temperature range 300-1210 K. Branching fractions of POCl(3)(-), POCl(2)(-), Cl(-), and Cl(2)(-) were measured. The results are analyzed by kinetic modeling, using electron attachment theory for the characterization of the nonthermal energy distribution of the excited POCl(3)(-?) anions formed and chemical activation-type unimolecular rate theory for the subsequent competition between collisional stabilization of POCl(3)(-?) and its dissociation to various dissociation products. Primary and secondary dissociations and∕or thermal dissociations of the anions are identified. The measured branching fractions are found to be consistent with the modeling results based on molecular parameters obtained from quantum-chemical calculations.     

The chemistry of cyanuric acid (H3C3N3O3) under high pressure and high temperature

We have studied cyanuric acid (H(3)C(3)N(3)O(3)) at static pressures up to 8.1 GPa and simultaneous temperatures up to 750 K, using primarily infrared absorption spectroscopy and visual observation. The corresponding phase diagram compares favorably with theoretical predictions of metastable organic materials. Two reactions were observed and characterized; both are irreversible. Below 2 GPa, melting is accompanied by a decomposition reaction, and upon cooling, cyanuric acid is not recovered. Above 2 GPa, heating results in a solid product recoverable at ambient conditions. Corresponding infrared spectra suggest that pressure leads to the formation of heterocycles of increasing complexity and biological potential, with the composition determined by the pressure of formation. Cyanuric acid is of interest at these conditions because it and its monomer, isocyanic acid, are "prebiotic" compounds found in stellar dust clouds, meteorites, and other remnants of the early Earth.     

Exploration of high pressure phase in LaGaO<Subscript>3</Subscript> and LaCrO<Subscript>3</Subscript>

Summary Structural phase transitions upon the application of high pressure in LaGaO₃ and LaCrO₃, which were prospected from diffraction and thermal analyses of phase transition under ambient pressure, were discovered by using high-pressure X-ray diffraction. It was revealed that the crystal structures of LaCrO₃ and LaGaO₃ changed completely from that of orthorhombic distorted perovskite to that of a rhombohedral distorted one upon the application of pressure higher than 5.4 and 3.0 GPa, respectively, at room temperature. The variation of lattice constants with pressure was investigated for the high-pressure rhombohedral phases of LaCrO₃ and LaGaO₃ and isothermal compressibility was estimated. The variation of lattice constants with pressure at room temperature in the high-pressure rhombohedral phase was compared with that with temperature at ambient pressure in high-temperature rhombohedral phase. It was found that the application of pressure decreased the crystal symmetry, which was opposite to the result in the case of increasing the temperature.     

Short-chain branching in γ-radiation-induced polymerization of ethylene

In an attempt to elucidate the mechanism of chain-branch formation in the polymerization of ethylene, the effect of reaction conditions on short-chain branching in γ-radiationinduced polymerization of ethylene was investigated by using infrared spectroscopy. The concentration of methyl groups, i.e., the frequency of short-chain branching, increases with temperature and pressure and is independent of ethylene conversion to polymer and radiation intensity. The number of methyl groups per polymer molecule increases almost proportionally with the degree of polymerization. These facts indicate that short-chain branching occurs mainly by the mechanism of intramolecular hydrogen transfer. The effect of pressure on the rate of chain branching can be postulated by considering the transition state to be six-membered rings in hydrogen transfer reactions. The activation energy of chain branching is found to exceed that of propagation by 6 kcal./mole.     

High-pressure structural behavior of GdAlO3 and GdFeO3 perovskites

The orthorhombic perovskites, GdAlO₃ and GdFeO₃, have been studied using single-crystal X-ray diffraction up to 8.52 and 8.13 GPa, respectively, in a diamond anvil cell at 298 K. The evolution of the structures of GdAlO₃ and GdFeO₃ involves compression of both the GdO₁₂ and the octahedral (AlO₆ and FeO₆) sites. The compression of the GdO₁₂ site is anisotropic in both perovskites, with the four longest Gd-O distances compressing more than the eight shorter Gd-O bond lengths, resulting in a decrease in the distortion of GdO₁₂ with pressure. In GdAlO₃, the GdO₁₂ site is less compressible than the AlO₆ site, resulting in an increase of both the interoctahedral Al-O1-Al and Al-O2-Al angles with increasing pressure. Thus GdAlO₃ perovskite becomes less distorted with increasing pressure. In GdFeO₃, the GdO₁₂ site displays a similar compressibility as the FeO₆ site, with little change in the Fe-O2-Fe angle with pressure but an increase of the Fe-O1-Fe tilting angle. Thus GdFeO₃ perovskite becomes less distorted with increasing pressure, but the change is not as pronounced as GdAlO₃. The high-pressure behavior of GdAlO₃ and GdFeO₃ is similar to orthorhombic YAlO₃ perovskite but contrasts with orthorhombic CaSnO₃, which becomes more distorted with increasing pressure.     

Phonon behavior of CaSnO3 perovskite under pressure

Raman scattering and x-ray diffraction studies of CaSnO(3) perovskite were performed under high-pressure conditions. This high-pressure study was motivated by a recent theoretical study predicting a phase transition in CaSnO(3) from GdFeO(3)-type perovskite to CaIrO(3)-type structure occurred at 12 GPa. Despite no obvious structure change up to a pressure of 26 GPa based on the x-ray diffraction data, high pressure Raman measurements revealed that some Raman modes disappeared upon compression; either merging into neighboring bands or vanishing. The signals for these Raman peaks were recovered during decompression. The measured pressure derivative of Raman shift (?ν∕?P) of CaSnO(3) ranged from ~1.29 to ~4.35, up to 20 GPa. Due to the lack of lattice dynamic study for CaSnO(3) perovskite, the mode symmetry for CaSnO(3) was tentatively assigned based on the empirical relation among Ca-bearing perovskites. The pressure derivative of the Raman shifts was found to be related to their mode vibrations: modes related to Ca and O shifts had a strong pressure dependence compared with those associated with oxygen octahedral rotation.