Effect of flexible polymers on the dielectric dispersion of rod-like macromolecules

The rotational diffusion of rod-like polar macromolecules (poly-γ-benzyl-l-glutamate or poly-n-hexylisocyanate) within entangled non polar polymer coils (polystyrene) is studied by dielectric absorption in solution. The dielectric increment as well as the rotatory diffusion constant is studied as a function of molecular weight of both components and increasing concentration of the non-polar polymer as well as the temperature. The classical theory of rotational diffusion is not obeyed if the viscosity of the polystyrene solution is taken as the medium viscosity. An increase in molecular aggregation on polystyrene addition is suspected.     

The osmotic pressure of concentrated protein and lipoprotein solutions and its significance to ultrafiltration

Side-by-side measurements were made of osmotic pressure and ultrafiltration flux from a stirred cell for separate saline solutions of the proteins, bovine serum albumin, bovine fibrinogen, human low density lipoprotein and for polyethylene oxide .in distilled water. Albumin osmotic pressures were large enough to conclude that concentration polarization limits ultrafiltrate flux mostly by decreasing the driving forceΔP -Δπ. For the other large macrosolutes, concentrated-solution osmotic pressures were so small that polarization probably limits flux at the usual levels of applied pressure by adding a hydrodynamic resistance (gel layer) in series with the membrane resistance.     

Thermodynamics of solvent extraction of thorium by solutions of HHTA and mixtures of HHTA and TBP

The changes in free energy, enthalpy and entropy for the extraction of thorium by solutions of thenoyltrifluoroacetone (HTTA) and mixtures of solutions of HTTA and tri-n-butylphosphate (TBP), in three diluents, viz. cyclohexane, benzene and chloroform, were determined using the solvent extraction data obtained at different temperatures. From these data the thermodynamic parameters associated with the formation of Th(TTA)₄ · TBP in the respective organic diluents were evaluated. Trends in the enthalpy changes were attributed to different degrees of association of the diluents with themselves and with the solutes present in them.     

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.     

Head-to-head polymers—II. Dilute solution properties of head-to-head polypropylene

The behaviour in dilute solution of head-to-head (H-H) polypropylenes, covering the range $\text{M}{}_{\mathrm{n}}\text{= 0.22}$ to 4.19 × 10⁴, has been studied in cyclohexane as solvent at 303 K. The data could be represented by two distinct Mark-Houwink equations describing the low and the high molecular weight regions. The unperturbed dimensions of (H-H) polypropylenes were found to be less than those for conventional atactic polypropylene in agreement with theoretical predictions. The theta temperature for (H-H) polypropylene in isoamylacetate was found to be 316 K. At this temperature the characteristic ratio was estimated to be 4.5 compared with 6.4 for atactic and syndiotactic polypropylene. The conclusion is that (H-H) placements in polypropylene increase the flexibility of the chain.     

Head-to-head polymers—I. The preparation and some properties of head-to-head polypropylene

Samples of head-to-head polypropylene have been prepared by the hydrogenation of two polydienes; 1,4-poly(2,4-hexadiene) and 1,4-poly(2,3-dimethyl-1,3-butadiene). Glass transition temperatures were found to be marginally lower than for conventional polypropylene suggesting that the head-to-head placements in the chain increased the polymer flexibility.     

The dependence of the kinetics of some simple outer-sphere electrode reactions on the nature of the electrode material

The kinetics of a number of simple inorganic electrode reactions that are known or expected to follow outer-sphere pathways have been examined at mercury, silver, platinum, and gold-aqueous interfaces in order to explore the effects of varying the electrode material on outer-sphere reactivity. The electroreduction kinetics of Co(III) ammine complexes exhibited only mild dependences on the nature of the electrode material which were compatible with the expected variations in double-layer effects. However, the electrooxidation of Cr²⁺ proceeded at strikingly higher overpotentials on the solid surfaces compared with mercury electrodes. Similar effects were also seen for the electrooxidation of V²⁺, Eu²⁺ and Ru²⁺ in the presence of Cr²⁺. Much larger rate constants were observed for these aquo reactions at solid surfaces in the absence of Cr²⁺, although Cr²⁺ had no influence on Co(NH₃)₆³⁺ electroreduction, or any reaction at mercury electrodes. It is speculated that the very large substrate effects upon the electrode kinetics of aquo couples arise from the influence of the inner-layer water structure on the reactant-solvent interactions experienced by these “structure-making” reactants at their plane of closest approach. The inhibiting influence of Cr²⁺ may be due to its ability to efficiently remove adsorbed catalytic contaminants by incorporation into a substitutionally inert Cr(III) electrooxidation product by means of a ligand-bridge mechanism.     

Effect of temperature and absorbed ionizing radiation doses on the electric and electronic properties of copper(II) complexes

A large number of copper(II) complexes derived from their related pyridine derivatives were prepared, crystallized and their characteristics established. The temperature dependence of d.c. electronic (electrical) conductivity and the electronic absorption properties of the materials under investigation were studied before and after exposure to various absorbed gamma does up to 10⁷ rads using a ⁶⁰Co gamma cell. The effect of gamma absorbed doses on the d.c. electrical conductivity and electronic absorption spectra of γ-irradiated samples are discussed on the basis of the effect of ionizing radiation firstly on metal—oxygen, and secondly on CC bonds regarding the substituent effect on their electronic delocalization and their geometrical structures.     

The nature of bridging and semi-bridging carbonyl groups

Calculations indicate the existence of “semi-bridging” bonding in Mn₂(CO)₁₀ but not in Re₂(CO)₁₀.     

The nature of sulfur bonding in thiopyrylium cation

Comparison of the PMR spectrum ofthiopyrylium cation with those of the oxygen (pyrylium cation) and nitrogen (pyridinium cation) analogs has suggested the unique electronic structure of the thiopyrylium cation. To investigate this structure the extended Hückel MO calculations have been carried out using two basis sets, one with and another without sulfur 3d orbitals. The electronic structure of thiopyrylium cation can be rationalized by the 3d orbital involvement of the S atom in the basis set. The primary effect of the involvement of 3d orbitals on the S atom is shown to be the electron transfer from the ring carbon fragment, in particular from the β ring carbons, to the S atom, with an accompanying increase in sulfur-α-carbon bond order.     

Effect of pore water and adsorbed moisture on the dielectric properties of green river oil shale

Moisture and pore water are found to have appreciable effects on the dielectric parameters of Green River oil shale. A regular decrease in the relative dielectric constant, ε′, and dielectric loss, ε″, with decreasing amount of adsorbed moisture and pore water is observed at 24°C for oil shale samples ranging in oil yields from ～6-～100 gallons per ton. The weak dependence of ε′ and ε″ on shale richness at frequencies in the range 50 Hz-1 MHz effectively rules out the application of dielectric techniques as an assay tool. The results are discussed in terms of interfacial polarization effects arising from the presence of adsorbed moisture and pore water in the oil shale matrix.     

Graph—theoretical approach to the calculation of physico-chemical properties of polymers

A topological extrapolation method for the calculation of various properties (melting points, refractive indices, specific rotation, etc.) of infinite linear polymers is developed. The rapid convergence of the oligomer extrapolation series results in very good agreement between calculated and experimental values. Comparison between the proposed method and other empirical or semi-empirical methods (the group addition method and the Pade-approximation) is also presented.     

A theoretical treatment of entropic repulsions by polymers

We consider a simple model of a random flight chain or length S confined between two parallel plates of area A separated by distance L. Adsorption of the polymer at the plate surfaces is neglected. The resulting pressure exerted on the plates due to configurational entropy is always repulsive. We obtain

     

Synthesis of polymers containing tertiary phosphine oxides using complex bases

Tertiary phosphine oxides have been prepared in excellent yield from primary alkyl halides or aromatic halides and activated sodium phosphinates obtained by reaction of dialkyl phosphine oxides with complex bases (NaNH₂/tBuONa). This reaction has been successfully applied to soluble and cross-linked bromopolystyrenes and to macroporous polystyrenes with bromooctyl substituents giving polymers which contain pendant phosphine oxide groups.     

Diffusion-controlled oxidation of polymers: A mathematical model

Mathematical modelling of the oxidation of a polymer, based on Fick's Law for diffusion of oxygen with reaction, with suitable boundary conditions produced an equation which combines the diffusion-free kinetics of the surface layers of the oxidising sample with the diffusion-controlled kinetics which predominate at greater depth. Comparison of the final, simplified, equation with literature results for oxidation rates versus film thickness showed excellent agreement with experiment. Attempts to fit to the experimental results an equation which assumes diffusion control from the film surface failed, indicating that the splitting of the film into two domains for the purpose of kinetic investigation was correct.     

Polymer-polymer interaction parameters in solvent/polymer/polymer ternary systems

Empirical equations defining the relationships between b₂₃ and χ₂₃ interaction parameters for the ternary systems toluene (1)/poly(dimethylsiloxane), PDMS, (2)/polystyrene, PS, (3) and benzene (1)/PDMS(2)/PS(3) have been determined. The dependences of both interaction parameters on the mean molecular weights of the macromolecular components have also been studied. A single dependence of b₂₃ (or χ₂₃) upon the mean molecular weight is found when both polymeric components have intermediate to high molecular weights. However, that single dependence is not found when the molecular size of polymer (2) is low.     

Study of the (210) face of gold in aqueous solutions

Among all the gold faces studied to date, the (210) face has the most negative pzc and therefore should be less affected by preoxidation than the other faces. But the (210) gold face-sodium fluoride solution interface is ideally polarizable only in a short range of potential. Nevertheless, differential capacity-potential curves have been tentatively exploited. There seems to be adsorption of the fluoride ions on the (210) face of gold. The inner-layer capacity-charge curves are discussed.     

Diffusion in surfactant solutions

The diffusion coefficients in water of Triton X-100 and sodium dodecyl sulfate were measured as a function of concentration using the Taylor dispersion technique. For Triton X-100, a nonionic surfactant, the diffusion coefficient drops from 7.4 × 10^-7 cm²/sec at 0.45 g/liter to 6.45 x 10^-7 cm²/sec at 5 g/liter. The diffusion coefficient of methyl yellow solubilized in Triton X-100 is close to that of the surfactant. This behavior is quantitatively consistent with a chemical equilibrium between monomer and micelle. For sodium dodecyl sulfate, an anionic surfactant, the diffusion coefficient increases from 1.76 x 10^-6 cm²/sec at 0.01 M to 4.53 x 10^-6 cm²/sec at 0.125 M. The increase is less when 0.1 M NaCl is added. The diffusion coefficient of the methyl yellow solubilized by the SDS is significantly less than that of the surfactant, particularly at low ionic strength. This behavior can be quantitatively explained by including electrostatic coupling between monomer, micelle, and counterion.