Investigation of the self-association of proflavine and acridine orange molecules in aqueous solution by 1H NMR

The chemical shifts of the protons in the proflavine and acridine orange molecules in aqueous solution were measured by ¹H NMR spectroscopy. The equilibrium constants for the association of the molecules and the chemical shifts of the protons in the monomers and associates were obtained from the concentration dependence of the proton chemical shifts. The most probable structures for the dimers of the dyes were calculated on the basis of the obtained chemical shifts, and a comparative analysis was made.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 3, pp. 373–376, May–June, 1987.     

Newtonian viscosity of polymer solutions over a wide range of compositions as a function of certain parameters determining it

Using solutions of various polymers in a large number of solvents as an example, the possibility of constructing a generalized characteristic for their viscosity, which is invariant relative to the molecular weight of the polymer and the nature of the solvent, is indicated. It is shown that the parameters characterizing the properties of individual macromolecular chains are the dimensions of the coils [], and the rheological effectiveness of interaction of the segments K_M retain their importance and quantities determining the viscous properties of the polymer solution over the whole range of compositions. A connection is established between the datum parameter K_M and the thermodynamic properties of dilute solutions of polymers, the flexibility of the polymer chain, and the energy of its intermolecular interaction.A. M. Gor'kii, Ural State University, Sverdlovsk. A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1110–1117, November–December, 1972.     

Effect of the molecular weight of polystyrene on the viscosity of concentrated solutions

The viscosity of solutions of polystyrene of various molecular weights (from 1.04 · 10² to 3.8 · 10⁵) in a poor solvent (decalin) and a good solvent (ethylbenzene) has been measured at temperatures from 15 to 70°C over a broad range of shear stresses from 10² to 10⁶ dyne/cm². The nature of the solvent has a considerable influence on the critical molecular weight and the absolute value of the viscosities of the solutions over the entire range of molecular weights and on the form of the flow curves of decalin solutions of polystyrene as a function of temperature. The heat of activation of viscous flow increases with increase in molecular weight and shear stress on the interval 20–80°C. The results obtained are explained in terms of the effect of the molecular weight of the polymer, the nature of the solvent, stress and temperature on structure formation in the solution and on the orientation of the macromolecules and structures in the flow process.Ural Gor'kii State University, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 920–926, September–October, 1970.     

Peculiarities of rheological behavior of filled polymer melts in uniaxial stretching

The peculiarities of theological behavior of filled polymer melts in uniaxial extension in a wide range of strain rates (from 2× 10^–5 to 1 × 10^–1 s^–1) have been studied. Linear polyethylene and 1,4-polybutadiene containing up to 21.5 vol.% of carbon black, silica, calcium carbonate or glass fibers were used. It has been found that the transition from uniform to nonunion stretching due to the neck formation is typical of all specimen compositions, when they approach steady-state straining. Depending on the structure and rheological characteristics of the compositions general conditions for this transition have been established. The general regularities for varying the rheological characteristics of filled polymers in the course of their uniform stretching have been recognized. These regularities depend on the molecular characteristics of the polymer matrix and the presence in the compositions of the structural framework of high disperse filler or the network formed by the entangled fibers. Using polyethylene compositions it has been shown that the introduction of small amounts of disperse or fibrous fillers can give rise to acceleration of the relaxation process in filled polymers.     

Generalized rheological characteristic of plastic disperse systems with polymeric and low-molecular dispersion media (matrices)

Analysis of literature data on the flow of polymeric and oligomeric compositions as well as on systems of low viscous dispersion media containing a high-disperse filler (carbon black, silica, high-disperse chalk) has been carried out. As the basic idea, a proposal is made that their viscosity anomaly is due not to the matrix viscosity anomaly, but to the gradual breakdown of the filler structural skeleton with increasing shear stress and shear rate . The viscosity anomaly of those compositions is determined by the zeroshear but not by the apparent matrix viscosity. A general relationship has been found to describe the flow of such systems depending on the zero-shear matrix viscosity values, ₀, their yield stress, _y , and filler volume concentration , whereK=4.9 andn=0.69 are constants.     

Influence of the solvent on the durability of cellulose acetate films formed from solutions

The authors examine the influence of the nature of the solvent on the time dependence of the strengths of films obtained from solutions of cellulose acetate in various solvents. They found that the durability of the films depends on the nature of the solvent. They have established that as the thermodynamic affinity of the solvent in the film-forming solutions gets worse, the durability of the films passes through a maximum; the nature of the solvent influences the parameter in the equation for the durability, which is responsible for changes in the structure of the polymer.V. I. Lenin Tadzhik State University, Dushanbe. A. M. Gor'kii Ural State University, Sverdlovsk. Translated from Mekhanika Polimerov, No. 2, pp. 360–362, March–April, 1974.     

Viscosity,rubber elasticity,and viscoelasticity of concentrated polymer solutions

The results of a comparative investigation of the effect of the nature of the polymer and the solvent on the viscosity, rubber elasticity, and viscoelasticity of concentrated polymer solutions in the region of linear mechanical behavior are presented. It is established that in the case of nonpolar polymers the solvent affects only the free volume of the solution, whereas for polar polymers it also affects the entanglement network. This leads to the equality of the viscosities of solutions of nonpolar polymers in different solvents when compared in corresponding states (relative to the glass transition temperature) and to the dependence of the shear modulus of solutions of polar polymers on the nature of the solvent and temperature. It is shown that there is a universal relaxation spectrum in the flow zone for solutions of different polydisperse polymers after normalization with the shear modulus and the natural relaxation time determined as the ratio of the viscosity to the shear modulus.A. M. Gor'kii Ural State University, Sverdlovsk, A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 729–736, July–August, 1973.