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1.
V.N. Tsvetkov P.N. Lavrenko L.N. Andreeva A.I. Mashoshin O.V. Okatova O.I. Mikriukova L.I. Kutsenko 《European Polymer Journal》1984,20(8):823-829
Translational diffusion, velocity sedimentation and viscosity in acetone as well as flow birefringence (FB) and viscosity in cyclohexanone have been investigated for cyanoethyl cellulose (CEC) with degree of substitution 2.6 in the range of M = (24.5?317) × 103. The dependences of [ν], So and Do on M were obtained. The value of the hydrodynamic constant is . According to hydrodynamic data, the equilibrium rigidity of CEC molecules is characterized by the length of the Kuhn segment and the coefficient of hindrance to intramolecular motion σ = 4.5-5.4. The hydrodynamic diameter of the chain is 8–14 Å. According to the FB data, the value of A is 260 Å. This value is in agreement with hydrodynamic data. The high value of optical anisotropy of the monomer unit, a| - a⊥ = 17.8 × 10?25 cm3, is in agreement with the structure and anisotropy of the substituting groups, and the investigation of orientation angles of FB leads to the conclusion that, apart from high equilibrium rigidity, CEC in solution is characterized by considerable kinetic chain flexibility. The data for CEC are compared with the characteristics of other cellulose esters and ethers. 相似文献
2.
For a number of fractions and unfractionated samples of polylaurolactam, molecular weights () were measured by the light-scattering method in a mixed solvent of m-cresol with 60 vol. % 2,2,3,3-tetrafluoropropanol; intrinsic viscosities were determined in m-cresol and 96% H2SO4, and the constants of the Mark-Houwink equation were calculated. The calculated values of the characteristic ratio of unperturbed dimensions (virtually identical for m-cresol and 96% H2SO4) were compared with the respective values for polypyrrolidone and polycaprolactam. It was found that the higher frequency of the CONH-groups reduces the rigidity of the polyamide chain. 相似文献
3.
J. Mulak 《Journal of solid state chemistry》1978,25(4):355-366
On the basis of the simplified model of the U4+ ion in a distorted axial crystal field, the temperature dependence of the magnetic susceptibilities of three U4+ sulfates, U(SO4)2 · 4H2O, U6O4(OH)4(SO4)6, and U(OH)2SO4, within the temperature range 4.2–300°K has been investigated and interpreted. This model proved to be successful, and the only parameters fitted empirically were the values of the crystal field splitting. The antiprismatic coordination (D4d) of the uranium ion in these compounds was confirmed and its electronic ground states were determined. The system of two singlets originating from the doublet 1 ± 3 > is the ground state of the uranium ion in U(SO4)2 · 4H2O. An analogous system of two singlets is the ground state in U6O4(OH)4(SO4)6. For U(OH)2SO4, the doublet | ± 2 > is the ground state above 21°K, whereas below this temperature it becomes split into the two singlets , probably because of a crystallographic distortion induced by the cooperative Jahn-Teller effect. Deviations from the D4d symmetry of the uranium ion coordination occurring in these compounds are discussed. 相似文献
4.
Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔHsoln = (7622 ± 24) calth mol?1 for a dilution of Cs2CrO4·21128H2O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔHsolno = (7512 ± 31) calth mol?1, whence the standard enthalpy of formation, ΔHf0(Cs2CrO4, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcalth mol?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S0(298 K), of BaCrO4 and PbCrO4 were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) calth K?1 mol?1, respectively. There is evidence that ΔHf0(SrCrO4, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO42?), bichromate (HCrO4?), and dichromate (Cr2O72?) ions. The new values at 298.15 K are as follows:
CrO42?(aq) | (13.8 ± 0.5) | ?(210.93 ± 0.45) | ?(174.8 ± 0.5) |
HCrO4?(aq) | (46.6 ± 1.8) | ?(210.0 ± 0.7) | ?(183.7 ± 0.5) |
Cr2O72?(aq) | (67.4 ± 3.9) | ?(356.5 ± 1.5) | ?(312.8 ± 1.0) |
α-Li2UO4 | ?(41.77±0.02) | ?(463.31±0.84) |
K2UO4 | ?(42.07±0.05) | ?(451.39±0.83) |
Rb2UO4 | ?(41.30±0.05) | ?(452.00±0.85) |
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