Oligomerisation anionique de l'ethylene—VI. Amorcage par le nBuLi complexe par diverses polyamines bitertiaires

In the field of anionic initiators of ethylene oligomerization, we have studied the reactivity of nBuLi complexed by tertiary amines such as tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA) and pentamethyldiethylenetriamine (PMDT). RMN shows high field shift of the —CH₂— protons next to the lithium. This shift is less important for TEEDA compared to those for TMEDA and PMDT. Steric hindrance due to the ethyl groups of TEEDA seems to forbid easy access of the nitrogen atoms to the lithium counter-ion. These results agree well with the kinetic studies which indicate the absence of aggregated species. The following equations have been established: $\text{V}{}_{\mathrm{p}}\text{= k}{}_{\mathrm{p}}\text{·K}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{D}}\text{[(}\text{nBuLi:TMEDA}\text{)}{}_2\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{Et}\text{]}$. and V_p = k′_p[nBuLi:TEEDA][Et]     

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; $\text{(}\text{dx}{}_{\mathrm{o}}\text{d}\text{T}\text{) = ?(4.0±0.5)×10}{}^{\mathrm{?4}}\text{K}{}^{\mathrm{?1}}$.     

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.     

The effect of nature of cation on the radical polymerizations of calcium,strontium and barium salts of P-styrenesulphonic acid in aqueous solutions

The kinetics of the homogeneous free radical polymerizations of divalent salts of styrenesulphonic acid (SSA) in water and water-salt solutions at 70° in the presence of ammonium persulphate has been investigated. It is shown that, for the concentration range from 0.12 to 0.3 mol/l for monomers, the initial rate of polymerization (V₀), the value of $\text{k}{}_{\mathrm{p}}\text{k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, the kinetic order with respect to monomer and the average molecular weight of the resulting polymer increase in the series Ca-SSA < Sr SSA < Ba SSA. In every case the kinetic order with respect to initiator is 0.5. The effect of cation on V₀ is more significant for smaller values of ionic strength (μ). With increasing μ the values of V₀ increase but the influence of cation radius on V₀ decreases; for large values of μ, V₀ does not depend on the cation.     

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.     

Transfer to monomer in the polymerization of N-(3-dimethylaminophenyl) maleimide and N-(3-dimethylamino-6-methylphenyl) maleimide

The kinetics of the homopolymerizations of styrene, N-(3-dimethylaminophenyl) maleimide (I) and N-(3-dimethylamino-6-methylphenyl) maleimide (II) in benzene and dimethylformamide, and the molecular weights of the polymers were studied. N-(3-Dimethylaminophenyl) succinimide, regarded as a model for polymer I, did not affect the polymerization of styrene. The data indicate degradative transfer of polymer radicals to dimethylformamide and pronounced transfer to monomers I and II (C_M ≈ 0.06–0.07). The value of $\text{k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for II is 0.09 $\text{dm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$$\text{mole}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$$\text{s}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$.     

A theory of viscosity of dilute and moderately concentrated polymer solutions

A model theory of viscosity η for moderately concentrated polymer solutions is based on the assumption of a “local viscosity” effect and intermolecular hydrodynamic and thermodynamic interactions. It is shown that η is given by

$\text{η = η}{}_{\mathrm{o}}\text{{1 + γc[η]}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{·}\text{exp}\text{H}{}_{\mathrm{o}}\text{RT}\text{aø}\text{1 ? aø}$

where γ is 0–0.4 and depends on the quality of the solvent, a varies between 0,4 and 0.8 and depends on the fraction of the “free volume” of the systems, H₀ is the activation energy of the solvent and π is the polymer volume concentration. The dependence of η and “activation energy” of π and T for various molecular weights and qualities of solvents is described quantitatively. Anomalous dependences of [η] and of η on M for low polymer are obtained. An expression for η is proposed:

$\text{η}\text{η}{}_{\mathrm{o}}{}^{\mathrm{<mtext>1\; ?\; 2</mtext><mtext>K</mtext>}}\text{= {1 + (1 ? 2K)c[η]}F(π)}$

where K is the Huggins-Martin coefficient and F(π) = 1 for most solutions when T is > T_g. For poor solvents the H vs c curve (where H is the activation energy of η of solution) has a minimum value at moderate concentrations. For good solvents, H depends slightly on the molecular weight according to an empirical equation:

$\text{H = H}{}_{\mathrm{o}}\text{+}\text{660}\text{α}{}^3\text{1}\text{n}\text{η}\text{η}{}_{\mathrm{o}}$

Expressions are given from the viscosities of solutions of miscible and also solutions of immiscible polymers.     

“Normal” and “cine” substitution in the thioalkoxy-dehalogenation of halogenobenzofurazans—III: Investigation on the solvent effect

The reaction of 4-chloro- and 4-chloro-7-deuteriobenzofurazan with MeS^-, isopropyl-S^-, and t-Butyl-S^- in different alcohols as solvents has been investigated. In going from methanol through isopropanol to t-butanol, a progressive decrease of the contribution of the cine-substitution as compared with the normal substitution pathway has been found. By proceeding in the same order, a decrease of the ratio and $\text{k}\text{MeS}{}^{\mathrm{?}}\text{k}{}_{\mathrm{<mtext>t</mtext>}}$-ButylS^? has also been observed.     

Primary radical termination in polymerization: Evaluation of the characteristic constant

Polymerization experiments with styrene in benzene at 60°, initiated by benzoyl peroxide, covering a wide range of concentration of both monomer and initiator are reported; the results cannot be explained in terms of the classical rate relationship with $\text{R}{}_{\mathrm{p}}\text{∝ [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{M}\text{]}$. Deviations were reflected in unexpected orders of monomer up to [M]^1·4 and of initiator down to [I]^0·42 when the initiator concentration is increased and monomer concentration is decreased. Based on the concept of primary radical termination, an equation, viz.

$\text{ln}\text{R}\text{p}\text{2}\text{[I][M]}{}^2\text{=}\text{ln}\text{2f}{}_{\mathrm{k}}\text{k}{}_{\mathrm{d}}\text{k}\text{p}\text{2}\text{k}{}_{\mathrm{t}}\text{?2}\text{k}{}_{\mathrm{prt}}\text{k}{}_{\mathrm{i}}\text{k}{}_{\mathrm{p}}\text{×}\text{R}{}_{\mathrm{p}}\text{[M]}{}^2$

is proposed. Semi-log plots of R_p²/[I] [M]² vs R_p/[M]² show a wide range of linearity; the characteristic constant k_prt/k_ik_p and also f_k can be obtained from the slope and intercept, respectively, k_prt, k_i and k_p are, respectively, the rate constants of primary radical termination, initiation and propagation and f_k is the efficiency of initiation, defined as the fraction of radicals which come out of the solvent cage and take part in initiation, primary radical termination and primary radical recombination. The definition of f_k is thus differentiated from the conventional efficiency of initiation. Finally, we have derived an equation which allows determination of the classical efficiency of initiation as a function of [I]/[M]² and also allows a correction of R_p in handling the above equation by taking into account the small amount of monomer consumed in initiation.     

Intramolecular relaxation of polystyrene in a theta solvent by photon-correlation spectroscopy

Photon-correlation spectroscopy has been used to measure the diffusion coefficient D and first-mode intramolecular relaxation time τ₁ of polystyrene in a theta solvent, cyclohexane at 34.5°C. Measurements were made on five narrow fractions ($\text{M}$_w = 2.88 × 10⁶ to 9.35 × 10⁶) as a function of concentration c, in the dilute regime. D varied linearly with c, D = D_o (I + k_Dc), with D_o = (1.4 ± 0.2) × 10^?4$\text{M}{}_{\mathrm{w}}{}^{\mathrm{?(0.508\pm 0.007)}}$ cm² s^?1. Although the values obtained for τ₁ were reproducible to within 5%, no systematic variation with c was detected. The results are fitted by the relation τ₁ = (7.7 ? 0.3) × 10^?8$\text{M}{}_{\mathrm{w}}{}^{\mathrm{(1.42\pm 0.05)}}$ μs, which agrees well with the theoretical expression of Zimm for the non-draining bead-and-spring model, modified for the light-scattering case.     

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

     

13.

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

J. M. Barrales-Rienda  P. A. Galera Gmez 《European Polymer Journal》1984,20(12):1213-1221

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.     

14.

A gas phase complex of acetylene and bromine: geometry,binding strength and charge transfer from rotational spectroscopy     

《Chemical physics letters》2001,331(1-2):39-50

     

15.

Preparation and properties of PdPSe single crystals     

James V. Marzik  Robert Kershaw  Kirby Dwight  Aaron Wold 《Journal of solid state chemistry》1982,44(3):382-387

Single crystals of PdPSe were shown to be n-type semiconductors. Weak Pauli paramagnetic behavior was observed, which is consistent with the presence of delocalized electrons. Electrical measurements showed a room-temperature resistivity ? = 70 ohm-cm, activation energy of resistivity E_a = 0.32 eV, and Hall mobility μ = 34 cm² V^?1 sec^?1. Photoelectronic measurements in aqueous solutions of $\text{I}{}^{\mathrm{?}}\text{I}{}^{\mathrm{?}}{}_3$ indicate that PdPSe has high quantum efficiencies below 800 nm. The indirect optical band gap is 1.28(2) eV.     

16.

Synthesis of homoleptic tris(organo-chelate)iridium(III) complexes by spontaneous ortho-metallation of electronrich olefin-derived N,N′-diarylcarbene ligands and the X-ray structures of fac-[Ir{CN(C6H4Me-p) (CH2)2NC6H3Me-p}3] and mer-Ir{CN(C6H4Me-p)(CH2)2NC6H3Me-p}2 {CN(C6H4Me-p)(CH2)2NC6H4Me-p}Cl (a product of HCl cleavage)     

Peter B. Hitchcock  Michael F. Lappert  Pilar Terreros 《Journal of organometallic chemistry》1982,239(2):C26-C30

Treatment of [{Ir(COD)(μ-Cl)}₂] with excess of the electron-rich olefin [$\text{CN(Ar)(CH}{}_2\text{)}{}_2\text{N}$Ar]₂ (abbreviated as (L^Ar)₂, Ar = C₆H₄Me-p or C₆H₄OMe-p) affords the ortho-metallated tricycle [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₃], which for Ar = C₆H₄Me-p (Ia) with HCL yields [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₂(L^Ar)]Cl (IV); X-ray data show that in IV there is an unexpectedly close Ir?C(o-aryl) contact (2;52(1) Å) involving the “free” L^Ar which compares with an IrC(o-aryl) distance of 2.09(3) Å in Ia or 2.07(3) Å in the ortho-metallated L^Ar ligand of complex IV.     

17.

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

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

.     

18.

Termination and transfer of the polymer chain to a maleimide derivative containing the azo group     

F. Hrabák  J. Lokaj 《European Polymer Journal》1979,15(7):701-705

The copolymerizations of N-(3-dimethylaminophenyl) maleimide (I) and 4-(2-chlorophenyl)azo-3-maleimido-N,N-dimethylaniline (II) with styrene were investigated; the copolymerization parameters of the pairs ($\text{I}\text{+}\text{styrene}$) and ($\text{II}\text{+}\text{styrene}$) and $\text{k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ hr I at 50° were determined; chain transfer to the maleimide ring of I was proved. The homopolymerization of styrene in the presence of 4-(2-chlorophenyl)azo-succinimide-N,N-dimethylaniline (III) was used to determine the ratio of the rate constant for addition of the polystyrene radical to the azo group in III to k_p for styrene.     

19.

On converting from the McMillan-Mayer framework I. Single-solvent system     

《Fluid Phase Equilibria》1998,145(2):255-268

     

20.

Electrical and magnetic properties and homogeneity ranges of mixed-valence cesium-vanadium oxides     

M. Nygren  B. Blom  B. Forslund  M. Wołcyrz 《Journal of solid state chemistry》1985,59(2):201-209

Single crystals of CsV₂O₅, Cs₂V₅O₁₃, Cs_xV₂O₅, and CsV₃O₇, grown from melts, have been subjected to electrical conductivity and magnetic susceptibility measurements. CsV₂O₅ and Cs₂V₅O₁₃ are insulators exhibiting Curie-Weiss' law behavior with p_eff close to $\text{1.73}\text{V}{}^{\mathrm{4+}}\text{ion}$. They are stoichiometric according to the X-ray studies. CsV₂O₅, which has a very limited composition range (x ≈ 0.30?;0.33), is a semiconductor with temperature-dependent paramagnetism ($\text{p}{}_{\mathrm{<mtext>eff</mtext>}}\text{=}\text{1.83}\text{V}{}^{\mathrm{4+}}\text{ion}$). Cs_xV₃O₇ (0.30 ? x ? 0.40) is antiferromagnetic with a Néel temperature of ≈230 K. The temperature variation of the lattice parameters of Cs_0.33V₃O₇ has been determined with a Bond-type diffractometer. The same crystal was used for the conductivity measurements, and together these studies indicate that the transition from the semiconducting antiferromagnetic state to the semiconducting paramagnetic state takes place stepwise. The observed properties are discussed with reference to the crystal structures of the compounds.     

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

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.     

Preparation and properties of PdPSe single crystals

Single crystals of PdPSe were shown to be n-type semiconductors. Weak Pauli paramagnetic behavior was observed, which is consistent with the presence of delocalized electrons. Electrical measurements showed a room-temperature resistivity ? = 70 ohm-cm, activation energy of resistivity E_a = 0.32 eV, and Hall mobility μ = 34 cm² V^?1 sec^?1. Photoelectronic measurements in aqueous solutions of $\text{I}{}^{\mathrm{?}}\text{I}{}^{\mathrm{?}}{}_3$ indicate that PdPSe has high quantum efficiencies below 800 nm. The indirect optical band gap is 1.28(2) eV.     

Synthesis of homoleptic tris(organo-chelate)iridium(III) complexes by spontaneous ortho-metallation of electronrich olefin-derived N,N′-diarylcarbene ligands and the X-ray structures of fac-[Ir{CN(C6H4Me-p) (CH2)2NC6H3Me-p}3] and mer-Ir{CN(C6H4Me-p)(CH2)2NC6H3Me-p}2 {CN(C6H4Me-p)(CH2)2NC6H4Me-p}Cl (a product of HCl cleavage)

Treatment of [{Ir(COD)(μ-Cl)}₂] with excess of the electron-rich olefin [$\text{CN(Ar)(CH}{}_2\text{)}{}_2\text{N}$Ar]₂ (abbreviated as (L^Ar)₂, Ar = C₆H₄Me-p or C₆H₄OMe-p) affords the ortho-metallated tricycle [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₃], which for Ar = C₆H₄Me-p (Ia) with HCL yields [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₂(L^Ar)]Cl (IV); X-ray data show that in IV there is an unexpectedly close Ir?C(o-aryl) contact (2;52(1) Å) involving the “free” L^Ar which compares with an IrC(o-aryl) distance of 2.09(3) Å in Ia or 2.07(3) Å in the ortho-metallated L^Ar ligand of complex IV.     

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

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

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Termination and transfer of the polymer chain to a maleimide derivative containing the azo group

The copolymerizations of N-(3-dimethylaminophenyl) maleimide (I) and 4-(2-chlorophenyl)azo-3-maleimido-N,N-dimethylaniline (II) with styrene were investigated; the copolymerization parameters of the pairs ($\text{I}\text{+}\text{styrene}$) and ($\text{II}\text{+}\text{styrene}$) and $\text{k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ hr I at 50° were determined; chain transfer to the maleimide ring of I was proved. The homopolymerization of styrene in the presence of 4-(2-chlorophenyl)azo-succinimide-N,N-dimethylaniline (III) was used to determine the ratio of the rate constant for addition of the polystyrene radical to the azo group in III to k_p for styrene.     

Electrical and magnetic properties and homogeneity ranges of mixed-valence cesium-vanadium oxides

Single crystals of CsV₂O₅, Cs₂V₅O₁₃, Cs_xV₂O₅, and CsV₃O₇, grown from melts, have been subjected to electrical conductivity and magnetic susceptibility measurements. CsV₂O₅ and Cs₂V₅O₁₃ are insulators exhibiting Curie-Weiss' law behavior with p_eff close to $\text{1.73}\text{V}{}^{\mathrm{4+}}\text{ion}$. They are stoichiometric according to the X-ray studies. CsV₂O₅, which has a very limited composition range (x ≈ 0.30?;0.33), is a semiconductor with temperature-dependent paramagnetism ($\text{p}{}_{\mathrm{<mtext>eff</mtext>}}\text{=}\text{1.83}\text{V}{}^{\mathrm{4+}}\text{ion}$). Cs_xV₃O₇ (0.30 ? x ? 0.40) is antiferromagnetic with a Néel temperature of ≈230 K. The temperature variation of the lattice parameters of Cs_0.33V₃O₇ has been determined with a Bond-type diffractometer. The same crystal was used for the conductivity measurements, and together these studies indicate that the transition from the semiconducting antiferromagnetic state to the semiconducting paramagnetic state takes place stepwise. The observed properties are discussed with reference to the crystal structures of the compounds.