Effect of solution viscosity

Figure 4. The effect of solution viscosity upon the log v K relationship of an...

Some researchers studied the effect of solution viscosity on the formation of PANI-CSA fibers [203,204]. They found that a stable polymer droplet was formed with adding 2 wt % poly(ethylene oxide) (PEO) into solution, whereas no fiber formation of PANI/CSA occurred in chloroform without PEO addition. 

Simons also conducted experiments to determine the effect of solution viscosity, dielectric constant, conductivity, and solvent volatility on the fiber forming process. Simm et invented a process by which they modified the electrode, using an aimular elec-... 

Effect of solution viscosity on fiber morphology. Reprinted with permission from reference 23. Copyright 1999 Elsevier. 

Effect of solution viscosity on nanofiber morphology studied in polymer/titania systems. 

CM Christensen. Effects of solution viscosity on perceived saltiness and sweetness. Percept Psychophys 28 347-353, 1980. 

The code reproduced shock-jump conditions well, but many details in the solution were lost because of the smearing effect of artificial viscosity. 

A kinetic study for the polymerization of styrene, initiated with n BuLi, was designed to explore the Trommsdorff effect on rate constants of initiation and propagation and polystyryl anion association. Initiator association, initiation rate and propagation rates are essentially independent of solution viscosity, Polystyryl anion association is dependent on media viscosity. Temperature dependency correlates as an Arrhenius relationship. Observations were restricted to viscosities less than 200 centipoise. Population density distribution analysis indicates that rate constants are also independent of degree of polymerization, which is consistent with Flory s principle of equal reactivity. 

Perrin model and the Johansson and Elvingston model fall above the experimental data. Also shown in this figure is the prediction from the Stokes-Einstein-Smoluchowski expression, whereby the Stokes-Einstein expression is modified with the inclusion of the Ein-stein-Smoluchowski expression for the effect of solute on viscosity. Penke et al. [290] found that the Mackie-Meares equation fit the water diffusion data however, upon consideration of water interactions with the polymer gel, through measurements of longitudinal relaxation, adsorption interactions incorporated within the volume averaging theory also well described the experimental results. The volume averaging theory had the advantage that it could describe the effect of Bis on the relaxation within the same framework as the description of the diffusion coefficient. 

Recent advances have greatly decreased the difficulties raised by these cautionary points. In particular, on-line viscosimetry and multi-angle lightscattering make it possible to determine the molecular weight and viscosity of samples as a function of elution volume. With such detectors, effects of solute-column packing interactions become unimportant, since the properties of narrow fractions can be measured. These detectors will be discussed in greater detail below. 

It follows from Eqs. (2.6.6), (2.6.8) and (2.6.10) that the presence of the solvent has two effects on the ionic mobility the effect of changing viscosity and that of changing the ionic radius as a result of various degrees of solvation of the diffusing particles. If the effective ionic radius does not change in a number of solutions with various viscosities and if ion association does not occur, then the Walden rule is valid for these solutions ... 

In this equation. Act is taken as the maximum possible surface tension lowering. Hence for a solute-free continuous phase, Aa is the difference between the interfacial tension for the solvent-free system and the equilibrium interfacial tension corresponding to the solute concentration in the dispersed phase. Equation (10-6) indicates a strong effect of the viscosity ratio k on the mass transfer coefficient as found experimentally (LI 1). For the few systems in which measurements are reported (Bll, Lll, 04), estimates from Eq. (10-6) have an average error of about 30% for the first 5-10 seconds of transfer when interfacial turbulence is strongest. 

Equation (31) is similar to Eq. (7) except that it takes into account the effect of kinematic viscosity on the eddy properties near the wall. An iterative solution is required for the solution of Eqs. (30) and (31). Throughout Deissler s recent analysis (D3) the Reynolds analogy has been assumed, and throughout the turbulent core Deissler shows that... 

The effects of broth viscosity on k a in aerated stirred tanks and bubble columns is apparent from Equations 7.37 and 7.41, respectively. These equations can be applied to ordinary non-Newtonian liquids with the use of apparent viscosity as defined by Equation 2.6. Although liquid-phase diffusivity generally decreases with increasing viscosity, it should be noted that at equal temperatures, the gas diffusivities in aqueous polymer solutions are almost equal to those in water. 

In contrast to this, Armstrong reported that for dilute solutions ( 10 ppm), the drag reduction is independent of the chemical nature of the polymer and relates only to effects on solution viscosity. 

The amplitude of shear velocity is a determinant of the degree of thixotropic destruction of a material s structure, independently of the frequency of vibration effect. The effect of reversible viscosity drop is also observed at ultrasonic frequencies. Vibrothixotropy of concentrated polyisobutylene (PIB) solution was sMudied earlier at a frequency of acoustic treatment of 18 kHz and an amplitude of up to 15 mcm74). The first difference of normal stresses determined by the degree of extrudate s swelling... 

Redistribution and Polymer Structure. The structure of DMP-DPP copolymers is probably determined by the relative rates of the polymerization reaction and the monomer-polymer redistribution reaction. In the DMP-DPP system, structure may be predicted simply by observing the effect on solution viscosity of the addition of one of the monomers to the growing polymer derived from the other monomer. When DPP is added to a DMP reaction mixture, the solution viscosity drops immediately almost to the level of the solvent, as redistribution converts the polymer already formed to a mixture of low oligomers ... 

In some cases, if we consider, for example, the slow motion of a solution of very long macromolecules, the effect of internal viscosity is negligible, so that the set of constitutive equations can be simplified and written as... 

Pokrovskii VN, Chuprinka VI (1973) The effect of internal viscosity of macromolecules on the viscoelastic behaviour of polymer solutions. Fluid Dyn 8(1) 13-19 Pokrovskii VN, Kokorin YuK (1984) Theory of viscoelasticity of dilute blends of linear polymers. Vysokomolek Soedin B 26 573-577 (in Russian)... 

As reported by Venkatassety [34], evaluation of the conductivity of dipolar aprotic solutions must take into account, in addition to ion pair association and triple ion formation, the possibility of strong ion-solvent interactions and the pronounced effect of solvent viscosity on the conductivity. A typical example is PC solution of Li salts, where the A0 values calculated (based on conductivity measurements) were found to be very low in spite of the high polarity of this solvent and the expected high degree of dissociation of the electrolytes, due to the high viscosity of this solvent. 

The viscosity of dilute polymer solutions is considerably higher than that of the pure solvent. The viscosity increase depends on the temperature, the nature of the solvent and polymer, the polymer concentration, and the sizes of the polymer molecules. This last dependence permits estimation of an average molecular weight from solution viscosity. The average molecular weight which is measured is the viscosity average A/v, which differs from those described so far in this text. Before viscosity increase data are used to calculate Afv of the solute it is necessary, however, to eliminate the effects of solvent viscosity and polymer concentration. The methods whereby this is achieved are described in this section. 

The term in brackets on the left-hand side of Eq. (3-37) is called the intrinsic viscosity or limiting viscosity number. It reflects the contribution of the polymeric solute to the difference between the viscosity of the mixture and that of the solvent. The effects of solvent viscosity and polymer concentration have been removed, as outlined earlier. It now remains to be seen how the term on the right-hand side of Eq. (3-37) can be related to an average molecular weight of a real polymer molecule. To do this we first have to express the volume V of the equivalent hydro-dynamic sphere as a function of the molecular weight A/ of a monodisperse solute. Later we substitute an average molecular weight of a polydisperse polymer for M in the monodisperse case. 

Ono and Ware"" have measured the absorption, emission, and excitation spectra, the fluorescence decay times, and the quantum yields of a series of substituted diphenylmethylenes in rigid matrices at low temperatures. Acean-thrylene shows S2- So emission in hexane with a yield of 0.017 and lifetime of 4.3 ns. The low-temperature fluorescence spectra of bis-2-naphthyl-alkanes and their derivatives have been studied. Excimer formation is an activated process. The fluorescence and absorption spectra of 1,1-diphenyl-ethylenes have been analysed in some detail by Gustav and Bolke. " The S — Si transitions in trans isomers of phenylnaphthylethylenes have been assigned by picosecond absorption spectroscopy. Effects of solvent viscosity and the role of conformers in the mechanism of isomerization are elucidated. The production of non-equilibrium conformer concentrations in glassy solutions of diarylethylenes at 77 K due to restrictions imposed by the solid matrix has also been reported. Free jet excitation and emission spectra of diphenyl-butadiene show clearly the lowest excited Ag state and give a lifetime of 52.8 ns for 0-0 excitation.Electric field-induced charges in the optical... 

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