Solution properties of polytrimethylhexamethylenterephthalamide (trogamid TR)

For the polyamide Trogamid T^R, good as well as θ-solvents are available. Determinations of molecular weights by ultracentrifugation, light scattering, osmometry, viscometry and gelchromatography (GPC) are reported. For DMF at 25° the relation

$\text{[η] = 0.02737}\text{M}{}^{0.706}{}_{\mathrm{w}}\text{cm}{}^3\text{g}{}^{\mathrm{?1}}$

was established, [η] = f(T) shows a maximum between ? 70° and + 120°. θ-temperatures are 142° for aniline and 62° for pyrroline, the latter having a negative temperature gradient. The unperturbed dimensions are calculated from the viscosity in θ-solvents and in DMF; for the latter, the Stockmayer-Fixman extrapolation was used. Molecular dimensions proved to be small in comparison with those of similar polymers. This effect is due to the three methyl side-groups for each chain unit sterically preventing a more stretched conformation.     

Mutual solubility of n-butanol + water under high pressures

The mutual solubilities of {xCH₃CH₂CH₂CH₂OH+(1-x)H₂O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: T_o(U.C.S.T.) = 397.85 K and x_o = 0.110 at 1 atm; $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(12.0±0.5)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at p < 400 atm and $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(7.0±0.7)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at 800 atm < p < 2500 atm; $\text{(}\text{dx}{}_{\mathrm{o}}\text{d}\text{T}\text{) = ?(4.0±0.5)×10}{}^{\mathrm{?4}}\text{K}{}^{\mathrm{?1}}$.     

Kinetics of the dispersion polymerization of acrylamide

Aqueous solutions of acrylamide were dispersed with non-ionic surfactants within isoparafinic hydrocarbons to particles of approx. 1 μm and polymerized in a batch reactor by water-soluble and oil-soluble azo-initiators at 42 to 57°C. The resulting conversion-time curves are S-shaped showing a strong gel effect. For maximum rate of polymerization, the following kinetic expressions were determined for the conditions investigated:

$\text{r}{}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}{}^{0.5}\text{C}{}_{\mathrm{<mtext>M,o</mtext>}}$

for water-soluble initiators;

${}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}\text{C}{}_{\mathrm{<mtext>E,o</mtext>}}{}^{\mathrm{?0.2}}$

For oil-soluble initiators, the overall rate constant k is a function of interface area and temperature. The interface area is dependent on the phase ratio, stirring speed and temperature. For constant interface areas, an activation energy of 26 kJ/mol was found. The overall activation energy of the polymerization is 88.2 kJ/mol, when temperature dependence of the interphase is not taken into account. Polymerization of acrylamide with oil-soluble initiators can be described at low conversions by a model which considers mass transfer of primary radicals, and to a lesser extent of initiator molecules, from the oil phase into the water phase as rate determining step and termination by primary radicals. The resulting molecular weights of the polymer are extremely high (10⁶g/mol) and depend on temperature, stirring speed and concentration of initiator, emulsifier and monomer.     

Dilute solution properties of poly(N-vinyl-3,6-dibromo carbazole)—III. Phase equilibrium studies

The phase relationships of poly(N-vinyl-3,6-dibromo carbazole) (PVK-3, 6-Br₂) were examined for four solvents, viz, o-chlorophenol, p-chloro-m-cresol, o-dichlorobenzene and bromobenzene. Upper critical solution temperatures (UCST) have been determined for solutions of PVK-3,6-Br, fractions in o-chlorophenol and p-chloro-m-cresol over the molecular weight range $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{× 10}{}^{\mathrm{?4}}\text{= 125.0}\text{to}\text{4.8}$. The Flory temperature, θ, obtained from UCST for the PVK-3,6-Br₂/o-chlorophenol and PVK-3,6-Br₂/p-chloro-m-cresol systems are 66.0 and 112.9°C, respectively. The θ-temperatures were checked against molecular weight and viscosity data to determine the Mark-Houwink equations for these two theta solvents, with satisfactory agreement. The relations are

$\text{[ν] = 27.5}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(o-}\text{chlorophenol}\text{, 60.0°}\text{C}$

$\text{[ν] = 30.2}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(p-}\text{chloro}\text{-m}\text{cresol}\text{, 112.9°}\text{C}$

The characteristic ratio C_∞ = 〈R²〉₀/nl² was found to be 16.6 in o-chlorophenol at 60.0°C and 17.6 in p-chloro-m-cresol at 112.9°C. The value of the characteristic ratio C_∞ of PVK-3,6-Br₂ is of the same order of that for poly(N-vinyl carbazole). This indicates that the bromine atoms at the 3 and 6 (meta) positions have only an inappreciable effect on the hindering potential for rotation about the CC bond. This agreement of C_∞ for both polymers may also be taken as indicating that the effect of interaction between polar groups at the m-position on the hindering potential for rotation is small. The phase diagrams of PVK-3,6-Br₂ obtained in o-dichlorobenzene and bromobenzene seem to be characteristic of organized phase structures such as those found in systems exhibiting thermoreversible gelation. Light scattering measurement on PVK-3,6-Br₂ dissolved in o-dichlorobenzene, a gelation promoting solvent, and tetrahydrofuran, a very good solvent, strongly indicate that the macromolecular species in o-dichlorobenzene contain some extent supermolecular structures (aggregates, association of chain segments, etc.). These characteristic structures of PVK-3,6-Br₂ in o-dichlorobenzene and bromobenzene at 25°C are also characterized by high values of the Huggins' constant k′; for tetrahydrofuran solutions, the k′ values were in the range normally found for many good solvent-polymer systems.     

Thermophysical properties of the intermetallic Mn3MN perovskites III. Heat capacity of the solid solution Mn3.2Ga0.8N

The heat capacity of the solid solution Mn_3.2Ga_0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at T_A = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at T_c ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are $\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}\text{= 15.16}$, $\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}\text{= 18.57}$, $\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{= 2896}\text{K}$, $\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{RT}\text{= 8.85}$. At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K^?2·mol^?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established.     

Heat capacity and thermodynamic functions of CsCrCl3 and RbCrCl3. Structural phase transitions

We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl₃ and RbCrCl₃. A first-order transition at T_c = (171.1±0.1) K was detected for CsCrCl₃. The RbCrCl₃ showed at T_c = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T₁ = (440±10) K a continuous transition was also detected. Furthermore, at T_N ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are

     

7.

Electronic conductivity in nonstoichiometric cerium dioxide     

R.N. Blumenthal  R.K. Sharma 《Journal of solid state chemistry》1975,13(4):360-364

The electrical conductivity of sintered specimens of nonstoichiometric CeO_2?x was measured as a function of temperature (750–1500°C) and oxygen pressure (1–10^?22 atm). The isothermal compositional dependence of the electrical conductivity of CeO_2?x was determined by combining recently obtained thermodynamic data, x = x(P_O2, T), with the conductivity data. The compositional and temperature dependence of the electrical conductivity may be represented by the expression

$\text{σ=410[x]e}{}^{\mathrm{<mtext>?(0.158+x)</mtext><mtext>kT</mtext>}}\text{(}\text{ohm cm}\text{)}{}^{\mathrm{?1}}$

over the temperature range 750–1500°C and from x = 0.001 to x = 0.1.This expression was rationalized in terms of the following simple relations for (a) the electron carrier concentration

$\text{n}{}_{\mathrm{ce}}\text{′}{}_{\mathrm{ce}}\text{=}\text{8x}\text{a}{}_0{}^3$

where n_Ce′Ce is the number of Ce′_Ce per cm³ and a₀ is the lattice parameter and (b) the electron mobility

$\text{μ=5.2(10}{}^{\mathrm{?2}}\text{)e}{}^{\mathrm{<mtext>?(0.158+x)</mtext><mtext>kT</mtext>}}\text{(}\text{cm}{}^2\text{/}\text{V sec}\text{)}$

.     

8.

Relation empirique entre la viscosite intrinseque et la masse moleculaire d'un polymere dissout dans un bon solvant     

Anastasios Dondos 《European Polymer Journal》1977,13(10):829-832

We propose the following empirical relationship between the intrinsic viscosity of a polymer and its molecular weight M.

$\text{{[η]?[η]}{}_{\mathrm{\theta }}\text{/[η][η]}{}_{\mathrm{\theta }}\text{=?Δρ}{}_{\mathrm{\infty }}\text{+}\text{A′}\text{M}\text{1}\text{2}$

[η] and [η]₀ are the intrinsic viscosities in a good solvent and in θ conditions respectively. Δ?, and A′ are constants characteristic of a system polymer-solvent. This relationship is valid for PS and PMMA in various good solvents and for a range of molecular weight from 3000 to 250,000. It is in this range that the Mark-Houwink-Sakurada equation is least applicable.     

9.

Nonstoichiometry and defect structure of the perovskite-type oxides La_1−xSr_xFeO_3−°     

Junichiro Mizusaki  Masafumi Yoshihiro  Shigeru Yamauchi  Kazuo Fueki 《Journal of solid state chemistry》1985,58(2):257-266

In order to elucidate the defect structure of the perovskite-type oxide solid solution La_1?xSr_xFeO_3?δ (x = 0.0, 0.1, 0.25, 0.4, and 0.6), the nonstoichiometry, δ, was measured as a function of oxygen partial pressure, P_O2, at temperatures up to 1200°C by means of the thermogravimetric method. Below 200°C and in an atmosphere of P_O2 ≥ 0.13 atm, δ in La_1?xSr_xFeO_3?δ was found to be close to 0. With decreasing log P_O2, δ increased and asymptotically reached $\text{x}\text{2}$. The value corresponding to $\text{δ =}\text{x}\text{2}$ was about ?10 at 1000°C. With further decrease in log P_O2, δ slightly increased. For LaFeO_3?δ, the observed δ values were as small as <0.015. It was found that the relation between δ and log P_O2 is interpreted on the basis of the defect equilibrium among Sr′_La (or V?_La for the case of LaFeO_3?δ), V^··_O, Fe′_Fe, and Fe^·_Fe. Calculations were made for the equilibrium constants K_ox of the reaction

$\text{1}\text{2}\text{O}{}_2\text{(g) + V}{}^{\mathrm{··}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= O}{}^{\mathrm{x}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe}}$

and K_i for the reaction

$\text{2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= Fe}{}^{\mathrm{\prime }}{}_{\mathrm{Fe}}\text{+ Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe·}}$

Using these constants, the defect concentrations were calculated as functions of P_O2, temperature, and composition x. The present results are discussed with respect to previously reported results of conductivity measurements.     

10.

PVC chlorination using fluorine as initiator     

G.P. Gambaretto  G.P. Talamini  R. Rettore  G.M. Paolucci 《European Polymer Journal》1974,10(6):511-517

The chlorination of PVC has been studied in a fluidized bed reactor, initiating the reaction with elementary fluorine. The reaction has been carried out at temperatures between 20° and 60° for various concentrations of chlorine and fluorine. The rate of reaction is given by the equation:

(1)$\text{x=}\text{k[}\text{Cl}{}_2\text{]}{}^{\mathrm{0·5}}\text{[}\text{F}{}_2\text{]t}\text{1+k[}\text{Cl}{}_2\text{]}{}^{\mathrm{0·5}}\text{[}\text{F}{}_2\text{]t}$

, temperature is given by

$\text{log}\text{k=}\text{3500}\text{4·57}\text{1}\text{T}\text{+0·707}$

.Equation (1) is satisfied also by data obtained from a small scale plant reactor. A reaction mechanism is proposed.     

11.

Evaluation of the type of polymer property average     

Z. Dobkowski 《European Polymer Journal》1984,20(3):265-267

A method for evaluation of the type of average, which is experimentally obtained for a given property of polydisperse polymer, is described. A multivariable power function

where P is the polymer property, $\text{M}{}_{\mathrm{x}}$ is the x-average molecular weight, q is the polydispersity degree, A_p, a and a_px are constants, and the a_px = 0 criterion (a_px being the polydispersity exponent) is used for this purpose.     

12.

Application of gel permeation chromatography and viscometry for characterization of branched polydisperse polycarbonate     

Z. Dobkowski  J. Brzeziński 《European Polymer Journal》1981,17(5):537-540

Gel permeation chromatography (GPC) and viscometry (V) methods have been combined for determination of long-chain branching in bisphenol-A polycarbonate (PC) by means of a branching factor $\text{g}{}_{\mathrm{v}}\text{=}\text{M}{}_{\mathrm{vg}}{}^1\text{/}\text{M}{}_{\mathrm{v}}{}^1$, where $\text{M}{}_{\mathrm{vg}}{}^1$ and $\text{M}{}_{\mathrm{v}}{}^1$ are the apparent viscosity-average molecular weights calculated from GPC data and from intrinsic viscosities [η] of the samples respectively. A linear dependence of g_v on molar % of branching agent has been obtained. The GPC data on PC samples have also been applied for verification of an earlier [η]?M relationship for branched polydisperse polymers.     

13.

A viscometric study of poly(methyl methacrylate) in 2-alkoxyethanols     

O. Quadrat  L. Mrkvičková 《European Polymer Journal》1981,17(11):1155-1159

θ-Conditions, the temperature coefficient of unperturbed dimensions of the macromolecules and the thermodynamic interaction parameters ψ and κ were determined for solutions of poly(methyl methacrylate) in 2-alkoxyethanols (methoxy, ethoxy and butoxy). The results for this series of solvents fit the data reported for other solvents and dln $\text{r}{}_0{}^2\text{/}\text{d}\text{T = 2.6 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$. The dependence of parameters ψ and κ exhibited deviations from the theoretical dependence, mainly near the limiting value ψ = 0.5.     

14.

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)     

I. Katime  A. Roig 《European Polymer Journal》1975,11(8):603-607

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

15.

Etude comparative des structures type K₄NiF₄ et pérovskite par la méthode des invariants     

Paul Poix 《Journal of solid state chemistry》1981,40(2):175-179

The study of K₂NiF₄ and perovskite structure type by the “method of invariants” leads to the relationship: $\text{(A-X)}{}_9\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? (A-X)}{}_{12}\text{=}\text{constant}$, where (A-X)₉ and (A-X)₁₂ are the invariant values associated with cation A in coordination number 9 and 12. In the case where A = K⁺ and X = F^?, we propose the relationship:

$\text{(K}{}^{\mathrm{+}}\text{?F)}{}_{\mathrm{R}}\text{= 2.832 R}{}^{\mathrm{<mtext>1</mtext><mtext>11.4</mtext>}}$

where R is the coordination number.     

16.

The surface tension of liquid copper     

D.A. Harrison  D. Yan  S. Blairs 《The Journal of chemical thermodynamics》1977,9(12):1111-1119

The surface tension of liquid copper of 99.999 mass per cent purity has been measured by the sessile drop method in the temperature range 1373 to 1861 K. The least-squares equation expressing the surface tension σ as a function of temperature T is:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= (1552±35) ? (0.176±0.023)T/}\text{K}$

The linear correlation of excess surface enthalpy $\text{H}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ and excess surface entropy $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ per unit area among σ(T) from the literature is also demonstrated. Estimation of $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ via the statistical electron-gas theory of Zadumkin and Pugachewich yields an equation for the calculation of recommended values for the surface tension of molten copper as a function of temperature:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= 1497 ? 0.174(T/}\text{K}\text{)}$

.     

17.

Comprehensive study of the vapour–liquid equilibria of the pure two-centre Lennard–Jones plus pointdipole fluid     

《Fluid Phase Equilibria》2003,209(1):29-53

     

18.

Determination of temperature dependence of limiting activity coefficients for a group of moderately hydrophobic organic solutes in water     

《Fluid Phase Equilibria》2002,201(1):135-164

     

19.

Application de la RPE à la localisation des substitutions isomorphiques dans les micas: Localisation du Fe³⁺ dans les muscovites et les phlogopites     

D. Olivier  J.C. Vedrine  H. Pezerat 《Journal of solid state chemistry》1977,20(3):267-279

Electron spin resonance spectra attributed to four Fe³⁺ centers designated O_a, O_b, T_a, T_b have been observed in crystals of muscovite and phlogopite. The results are discussed using the spin Hamiltonian

with g_e ～ 2.002. The angular variation of the resonance lines is used to determine the ESR axes of the four different sites. Two species are octahedrally coordinated (O_a and O_b) and are assigned to two different surroundings of Fe³⁺ in the octahedral sheet. The remaining two species (T_a and T_b) may be assigned to the tetrahedral FeO₄. The T_a sites have a symmetry axis lying along one of the FeO bonds. The symmetry axis is created by an excess of negative charge on the oxygen bound to the neighboring tetrahedral substitution. Rhombic symmetry of the T_b sites is due to the presence of fluorine anions substituting some hydroxyl ions. One of the ESR axes is directed toward the fluorine ion.     

20.

General approach to polymer properties dependent on molecular characteristics     

Z. Dobkowski 《European Polymer Journal》1981,17(11):1131-1144

The general equation

where P is a polymer property, Π is the sign of product, A is a constant, v_i is the ith variable and a_i is the exponent of ith variable, has been proposed for the dependence of some polymer properties on molecular weight, molecular weight distribution and long-chain branching. The data confirming the proposed equation have been taken from published theoretical and experimental papers on intrinsic viscosity, melt viscosity and glass transition temperature, as well as on viscosity of polymer solutions. Examples of application are given.     

	$\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}$	$\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}$	$\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{K}$	$\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0}}\text{RT}$
CsCrCl3	15.38	26.49	3503.2	14.735
RbCrCl3	15.76	25.99	3556.8	14.384

Electronic conductivity in nonstoichiometric cerium dioxide

The electrical conductivity of sintered specimens of nonstoichiometric CeO_2?x was measured as a function of temperature (750–1500°C) and oxygen pressure (1–10^?22 atm). The isothermal compositional dependence of the electrical conductivity of CeO_2?x was determined by combining recently obtained thermodynamic data, x = x(P_O2, T), with the conductivity data. The compositional and temperature dependence of the electrical conductivity may be represented by the expression

$\text{σ=410[x]e}{}^{\mathrm{<mtext>?(0.158+x)</mtext><mtext>kT</mtext>}}\text{(}\text{ohm cm}\text{)}{}^{\mathrm{?1}}$

over the temperature range 750–1500°C and from x = 0.001 to x = 0.1.This expression was rationalized in terms of the following simple relations for (a) the electron carrier concentration

$\text{n}{}_{\mathrm{ce}}\text{′}{}_{\mathrm{ce}}\text{=}\text{8x}\text{a}{}_0{}^3$

where n_Ce′Ce is the number of Ce′_Ce per cm³ and a₀ is the lattice parameter and (b) the electron mobility

$\text{μ=5.2(10}{}^{\mathrm{?2}}\text{)e}{}^{\mathrm{<mtext>?(0.158+x)</mtext><mtext>kT</mtext>}}\text{(}\text{cm}{}^2\text{/}\text{V sec}\text{)}$

.     

Relation empirique entre la viscosite intrinseque et la masse moleculaire d'un polymere dissout dans un bon solvant

We propose the following empirical relationship between the intrinsic viscosity of a polymer and its molecular weight M.

$\text{{[η]?[η]}{}_{\mathrm{\theta }}\text{/[η][η]}{}_{\mathrm{\theta }}\text{=?Δρ}{}_{\mathrm{\infty }}\text{+}\text{A′}\text{M}\text{1}\text{2}$

[η] and [η]₀ are the intrinsic viscosities in a good solvent and in θ conditions respectively. Δ?, and A′ are constants characteristic of a system polymer-solvent. This relationship is valid for PS and PMMA in various good solvents and for a range of molecular weight from 3000 to 250,000. It is in this range that the Mark-Houwink-Sakurada equation is least applicable.     

Nonstoichiometry and defect structure of the perovskite-type oxides La1−xSrxFeO3−°

In order to elucidate the defect structure of the perovskite-type oxide solid solution La_1?xSr_xFeO_3?δ (x = 0.0, 0.1, 0.25, 0.4, and 0.6), the nonstoichiometry, δ, was measured as a function of oxygen partial pressure, P_O2, at temperatures up to 1200°C by means of the thermogravimetric method. Below 200°C and in an atmosphere of P_O2 ≥ 0.13 atm, δ in La_1?xSr_xFeO_3?δ was found to be close to 0. With decreasing log P_O2, δ increased and asymptotically reached $\text{x}\text{2}$. The value corresponding to $\text{δ =}\text{x}\text{2}$ was about ?10 at 1000°C. With further decrease in log P_O2, δ slightly increased. For LaFeO_3?δ, the observed δ values were as small as <0.015. It was found that the relation between δ and log P_O2 is interpreted on the basis of the defect equilibrium among Sr′_La (or V?_La for the case of LaFeO_3?δ), V^··_O, Fe′_Fe, and Fe^·_Fe. Calculations were made for the equilibrium constants K_ox of the reaction

$\text{1}\text{2}\text{O}{}_2\text{(g) + V}{}^{\mathrm{··}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= O}{}^{\mathrm{x}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe}}$

and K_i for the reaction

$\text{2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= Fe}{}^{\mathrm{\prime }}{}_{\mathrm{Fe}}\text{+ Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe·}}$

Using these constants, the defect concentrations were calculated as functions of P_O2, temperature, and composition x. The present results are discussed with respect to previously reported results of conductivity measurements.     

PVC chlorination using fluorine as initiator

The chlorination of PVC has been studied in a fluidized bed reactor, initiating the reaction with elementary fluorine. The reaction has been carried out at temperatures between 20° and 60° for various concentrations of chlorine and fluorine. The rate of reaction is given by the equation:

(1)$\text{x=}\text{k[}\text{Cl}{}_2\text{]}{}^{\mathrm{0·5}}\text{[}\text{F}{}_2\text{]t}\text{1+k[}\text{Cl}{}_2\text{]}{}^{\mathrm{0·5}}\text{[}\text{F}{}_2\text{]t}$

, temperature is given by

$\text{log}\text{k=}\text{3500}\text{4·57}\text{1}\text{T}\text{+0·707}$

.Equation (1) is satisfied also by data obtained from a small scale plant reactor. A reaction mechanism is proposed.     

Evaluation of the type of polymer property average

A method for evaluation of the type of average, which is experimentally obtained for a given property of polydisperse polymer, is described. A multivariable power function

where P is the polymer property, $\text{M}{}_{\mathrm{x}}$ is the x-average molecular weight, q is the polydispersity degree, A_p, a and a_px are constants, and the a_px = 0 criterion (a_px being the polydispersity exponent) is used for this purpose.     

Application of gel permeation chromatography and viscometry for characterization of branched polydisperse polycarbonate

Gel permeation chromatography (GPC) and viscometry (V) methods have been combined for determination of long-chain branching in bisphenol-A polycarbonate (PC) by means of a branching factor $\text{g}{}_{\mathrm{v}}\text{=}\text{M}{}_{\mathrm{vg}}{}^1\text{/}\text{M}{}_{\mathrm{v}}{}^1$, where $\text{M}{}_{\mathrm{vg}}{}^1$ and $\text{M}{}_{\mathrm{v}}{}^1$ are the apparent viscosity-average molecular weights calculated from GPC data and from intrinsic viscosities [η] of the samples respectively. A linear dependence of g_v on molar % of branching agent has been obtained. The GPC data on PC samples have also been applied for verification of an earlier [η]?M relationship for branched polydisperse polymers.     

A viscometric study of poly(methyl methacrylate) in 2-alkoxyethanols

θ-Conditions, the temperature coefficient of unperturbed dimensions of the macromolecules and the thermodynamic interaction parameters ψ and κ were determined for solutions of poly(methyl methacrylate) in 2-alkoxyethanols (methoxy, ethoxy and butoxy). The results for this series of solvents fit the data reported for other solvents and dln $\text{r}{}_0{}^2\text{/}\text{d}\text{T = 2.6 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$. The dependence of parameters ψ and κ exhibited deviations from the theoretical dependence, mainly near the limiting value ψ = 0.5.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

Etude comparative des structures type K4NiF4 et pérovskite par la méthode des invariants

The study of K₂NiF₄ and perovskite structure type by the “method of invariants” leads to the relationship: $\text{(A-X)}{}_9\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? (A-X)}{}_{12}\text{=}\text{constant}$, where (A-X)₉ and (A-X)₁₂ are the invariant values associated with cation A in coordination number 9 and 12. In the case where A = K⁺ and X = F^?, we propose the relationship:

$\text{(K}{}^{\mathrm{+}}\text{?F)}{}_{\mathrm{R}}\text{= 2.832 R}{}^{\mathrm{<mtext>1</mtext><mtext>11.4</mtext>}}$

where R is the coordination number.     

The surface tension of liquid copper

The surface tension of liquid copper of 99.999 mass per cent purity has been measured by the sessile drop method in the temperature range 1373 to 1861 K. The least-squares equation expressing the surface tension σ as a function of temperature T is:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= (1552±35) ? (0.176±0.023)T/}\text{K}$

The linear correlation of excess surface enthalpy $\text{H}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ and excess surface entropy $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ per unit area among σ(T) from the literature is also demonstrated. Estimation of $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ via the statistical electron-gas theory of Zadumkin and Pugachewich yields an equation for the calculation of recommended values for the surface tension of molten copper as a function of temperature:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= 1497 ? 0.174(T/}\text{K}\text{)}$

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Application de la RPE à la localisation des substitutions isomorphiques dans les micas: Localisation du Fe3+ dans les muscovites et les phlogopites

Electron spin resonance spectra attributed to four Fe³⁺ centers designated O_a, O_b, T_a, T_b have been observed in crystals of muscovite and phlogopite. The results are discussed using the spin Hamiltonian

with g_e ～ 2.002. The angular variation of the resonance lines is used to determine the ESR axes of the four different sites. Two species are octahedrally coordinated (O_a and O_b) and are assigned to two different surroundings of Fe³⁺ in the octahedral sheet. The remaining two species (T_a and T_b) may be assigned to the tetrahedral FeO₄. The T_a sites have a symmetry axis lying along one of the FeO bonds. The symmetry axis is created by an excess of negative charge on the oxygen bound to the neighboring tetrahedral substitution. Rhombic symmetry of the T_b sites is due to the presence of fluorine anions substituting some hydroxyl ions. One of the ESR axes is directed toward the fluorine ion.     

General approach to polymer properties dependent on molecular characteristics

The general equation

where P is a polymer property, Π is the sign of product, A is a constant, v_i is the ith variable and a_i is the exponent of ith variable, has been proposed for the dependence of some polymer properties on molecular weight, molecular weight distribution and long-chain branching. The data confirming the proposed equation have been taken from published theoretical and experimental papers on intrinsic viscosity, melt viscosity and glass transition temperature, as well as on viscosity of polymer solutions. Examples of application are given.