Model system for concentrated electrolyte solutions: Thermodynamic and transport properties of ethylammonium nitrate in acetonitrile and in water

Ethylammonium nitrate (ETAN), a low melting fused salt which is completely miscile in water and in many non-aqueous solvents, was used as a model system for the study of concentrated non-aqueous electrolyte solutions. Acetonitrile (AN) was chosen as a representative aprotic solvent. Some data were also obtained for water as solvent. The properties investigated over the whole mole fraction range, many as a function of temperature, were solid-liquid phase diagram, volume, heat capacity, conductivity and viscosity. Most properties in both solvents vary in a regular fashion over the whole mole fraction range and the properties at high concentration rapidly tend to those of the molten salt. The apparent volumes and heat capacities vary linearly with lnX₂ over a large mole fraction range. There is evidence of significant association in AN (K _A =1094 l-mol⁻) but not in water. The low concentration thermodynamic data were fitted with an association model using the above K _A to obtain the partial molar quantities of ETAN at infinite dilution and in the associated state. These latter values are of the same magnitude as the molar quantities of the molten electrolyte.     

高分子量聚苯硫醚树脂的合成

用H_2S、NaOH、p-C_6H_4Cl_2为原料,以Na_3PO_4作助剂,在六甲基磷酰三胺中进行常压缩聚反应4～5 h,得到线型、结晶性的高分子量聚苯硫醚。熔点>290℃,热分解温度>500℃,熔融低切变粘度为0.30～68.0×10~3Pa(303℃测定)。产品直接作抽丝试验,得到高分子量聚苯硫醚纤维。本法设备简单、操作容易、反应体系活性高、溶剂稳定。     

Prediction of the non-Newtonian viscosity and shear stability of polymer solutions

The structure-property relationships derived here permit the prediction of both the zero-shear viscosity ₀, as well as the shear rate dependent viscosity . Using this molecular modeling it is now possible to predict over the whole concentration range, independently of the molecular weight, polymer concentration and imposed shear rate. However, the widely accepted concept: dilute — concentrated, is insufficient. Moreover it is necessary to take five distinct states of solution into account if the viscous behavior of polymeric liquids is to be described satisfactorily. For non-homogeneous, semi-dilute (moderately concentrated) solutions the slope in the linear region of the flow curve (= must be standardized against the overlap parameterc · []. As with the ₀-M-c-relationship, a-M -c- relationship can now be formulated for the complete range of concentration and molecular weight. Furthermore, it is possible to predict the onset of shear induced degradation of polymeric liquids subjected to a laminar velocity field on the basis of molecular modeling. These theoretically obtained results lead to the previously made ad hoc conclusion (Kulicke, Porter [32]) that, experimentally, it is not possible to detect the second Newtonian region.Roman and Italian symbols a exponent of the Mark-Houwink relationship - b exponent of the third term of the ₀-M -c relationship - c concentration /g · cm^–3 - E number of entanglements per molecule - F(r) connector tension - f function - G _i ^A shear modulus; A indicates that it /Pa has been evaluated by a transient shear flow experiment; i is the shear rate to whichG ^A refers to - G storage modulus /Pa - G _p plateau modulus /Pa - H() relaxation spectrum /Pa - h shift factor (₀/_r) - K _H Huggins constant - K _b third constant of the ₀-M -c relationship - K constant of the Mark-Houwink relationship - M molecular weight /g · mol^–1 - M _e molecular weight between two /g · mol^–1 entanglement couplings - N number of segments per molecule - n slope in the power-law region of the flow curve - p p-th mode of the relaxation time spectrum - R gas constant /8.314 J·K^–1·mol^–1 - r direction vector - T temperature /K Greek symbols ß reduced shear rate - shear rate /s^–1 - shear viscosity /Pa·s - _s solvent viscosity /Pa·s - _sp specific viscosity - ₀ zero-shear viscosity /Pa·s - apparent viscosity at shear rate - reduced viscosity - viscosity of polymeric liquid in /Pa·s the second Newtonian region - [] intrinsic viscosity/cm³·g^–1 - screening length/m - /g·cm ^–3 density - relaxation time/s - ₀ experimentally derived relaxation time/s - angular frequency of oscillation Indices conc concentrated - corr slope corrected - cr critical - deg degradation - e entanglement - exp experimental - mod moderately concentrated/semi-dilute - n number average - p polymer - R Rouse - rep reptation - s solvent - sp specific - theo theoretical - weight average - relaxation time - o experimental or steady state - * critical - ** transition moderately conc. — conc. - + transition dilute — moderately cone. Paper presented at the 2nd bilateral U.S.-West German Polymer Symposium, Yountville, the 7th–11th September 1987.     

Structure and properties of new ionic liquids based on alkyl- and alkenyltrifluoroborates.

A new series of low-melting, low-viscosity, hydrophilic ionic liquids, which comprise 1-ethyl-3-methylimidazolium ([EMI]+) and alkyl(alkenyl)trifluoroborate anions ([RBF3]-, R=n-C(m)H(2m+1) (m=1-5), CH2CH), were prepared and characterized. The phase-transition behavior, thermal stability, density, viscosity, conductivity, and surface tension of these salts were measured. The influence of the structural variations, such as changing the length and fluorination of the alkyl chain (R) in the anion [RBF3]-, on the above properties was extensively investigated. The low viscosity of these [RBF3]- salts suggests that a high degree of freedom and/or a somewhat flat-shaped feature in the anion make an important contribution to reducing the viscosity. The Walden products for each salt are not constant and vary with temperature, which suggests that the ions in these salts are not completely dissociated.     

Measurement of mutual diffusion coefficients,densities, viscosities,and osmotic coefficients for the system KSCN-H2O at 25°C

Mutual diffusion coefficients measured on the volume-fixed frame of reference are reported for KSCN-H₂O at 25°C over the concentration range 0.0 to 10.26 mol-dm^–3. The diffusion coefficient at infinite dilution was obtained from limiting ionic equivalent conductances of K⁺ and SCN^–. Low concentration conductances of KSCN-H₂O at 25°C used to obtain the limiting ionic equivalent conductance of SCN^– are reported. Values of density and viscosity for this system are reported from 0.0 to 10.30 mol-dm^–3. Osmotic coefficienss of KSCN-H₂O at 25°C were measured by the isopiestic method. These are reported over the concentration range of 0.30 to 24.94 molal (saturation). Values of thermodynamic diffusion coefficients for the concentration range 0.0 to 10.26 mol-dm^–3 are tabulated. Results are compared to other potassium salts with monovalent anions at 25°C.     

Linear all-ortho oligomers of phenol–formaldehyde resins. I. Preparations,characterizations, and solution properties

Three kinds of all-ortho methylene-linked phenolic oligomers, i.e., 4-tert-butylphenol (BP), phenol (AO), and O-methylated BP (BPM), were prepared with good yields and their dilute solution properties were studied. In acetone, all of these oligomers are highly solvated and molecularly dispersed. In chloroform, however, AO and BP molecules strongly form hydrogen bonds among themselves. By intramolecular and intermolecular hydrogen-bondings, a large portion of the dimers and the trimers of AO and BP associate to form bimolecular aggregates in chloroform, assuming pseudo-cyclic conformations analogous to calix [4] arene and calix [6] arene, respectively. By intramolecular hydrogen-bonding, the tetramers and the hexamers also form pseudo-cyclic conformations by themselves in chloroform. © 1993 John Wiley & Sons, Inc.     

Electrophoretic behaviour and viscosities of metal oxides in mixed surfactant systems

 The electrokinetic behavior and viscosity of anatase and alumina in mixed-surfactant solutions were investigated. Sodium dodecylsulfate and nonionic polyoxyethylene ethers were investigated as model surfactants. Pure nonionic surfactants adsorbed on anatase and coated the particles, so that the zeta potential was nearly zero near the critical micelle concentration of surfactant. At higher surfactant concentrations, an increase in the zeta potentials was observed, suggesting a change in the microstructure of the adsorbed layer. Addition of nonionic surfactant to positively charged anatase and alumina with some preadsorbed sodium dodecylsulfate reversed the surface charge of the oxide to negative, indicating enhanced coadsorption of the anionic surfactant. At higher concentrations of the nonionic surfactant, the charge reversed back to positive. Nonionic surfactants did not reverse the surface charge of these oxides in the absence of the anionic surfactant. Coenhanced adsorption of nonionic and anionic surfactants was used to stabilize alumina at the isoelectric point, where neither surfactant adsorbed appreciably on its own. These results suggest a dramatic change in conformation of the surfactant chains in mixed systems. Further explanation and justification of the proposed changes in adsorbed surfactant conformation require spectroscopic evidence. Received: 12 March 1997 Accepted: 22 July 1997     

聚氧化乙烯水溶液粘度的测定

测定了不同分子量聚氧化乙烯(PEO)在水溶液中的粘度，发现在低浓度区高分子溶液比浓粘度出现负偏离。用高分子溶液流过时间对浓度作图的外推值t0^*重新计算相对粘度，则高分子溶液比浓粘度与浓度之间满足线性关系。不同分子量PEO水溶液流过时间对浓度作图的外推值t0^*是完全一致的。利用纯溶剂在粘度计中流过时间的改变确定了高分子在毛细管管壁上吸附层的厚度，发现PEO在毛细管管壁上吸附层厚度与分子量无关。     

Densities,Apparent Molar Volumes and Viscosities of Concentrated Aqueous NaNO<Subscript>3</Subscript> Solutions at Temperatures from 298 to 607 K and at Pressures up to 30 MPa

Densities of four (2.124, 2.953, 5.015 and 6.271 mol-kg⁻¹) and viscosities of eight (0.265, 0.503, 0.665, 1.412, 2.106, 2.977, 5.015 and 6.271 mol-kg⁻¹) NaNO₃(aq) solutions have been measured with a constant-volume piezometer immersed in a precision liquid thermostat and using capillary flow techniques, respectively. Measurements were made at pressures up to 30 MPa. The temperature range was 298–607 K for the density measurements and 298–576 K for the viscosity measurements. The total uncertainty of density, viscosity, pressure, temperature and composition measurements were estimated to be less than 0.06%, 1.6%, 0.05%, 15 mK and 0.02%, respectively. The temperature, pressure and concentration dependence of density and viscosity of NaNO₃(aq) solutions were studied. The measured values of density and viscosity of NaNO₃(aq) were compared with data and correlations reported in the literature. Apparent molar volumes were derived using the measured density values. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for strong electrolytes. The values of the viscosity A-, B-, D- and F-coefficients of the extended Jones–Dole equation for the relative viscosity (η/η₀) of NaNO₃(aq) solutions were evaluated as a function of temperature. The derived values of the viscosity A- and B-coefficients were compared with the results predicted by Falkenhagen–Dole theory of electrolyte solutions and calculated with the ionic B-coefficient data.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS( 2,6-DI- TERT-B UTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95 × 105 can be prepared at 40℃ when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.