Viscosity reduced specific

Figure 1. Effect of calcium on zero shear rate reduced specific viscosity of HPAM.

Table II. Relative Viscosities and (rirel) and Reduced Specific Viscosities (risp/c) °f Polymer Solutions Passed...

If this value is divided by the concentration c of the polymer in solution, one obtains the reduced specific viscosity, v[ plc. 

It may seem confusing to introduce yet another type of viscosity. In fact, there are many other types of viscosity (see Table 4.5), but we will concentrate on the intrinsic viscosity for polymer solutions. The intrinsic viscosity is important because it has been found to correlate well with a number of important parameters, including polymer molecular weight and type of solvent. Note that if Eq. (4.23) is truncated to the first two terms, the intrinsic viscosity is the same as the reduced specific viscosity, r]sp, of Table 4.5. 

The concept of a unique hydrodynamic volume for all rodlike polymers was derived from examination of the Mark-Houwink constants, K and a, of the equation [rj ] = KMa. Macromolecules with values of a greater than unity are commonly accepted to be stiff or rigid rods. However, it was also found that such molecules (even for values of a less than unity) obey a relation illustrated by close concordance with the curve in Fig. lb (13) flexible, branched or otherwise irregular polymers, on the other hand, show dispersion around the upper part of the curve. The straight line curve in Fig. lb implies that the constants K and a are not independent parameters for the regular macromolecules to which they apply. Poly (a- and polyQJ-phenylethyl isocyanide) fall on this line the former has a value of a > 1 while the latter has a value a < 1 (14) both polymers give linear concentration dependence of reduced specific viscosity for fractionated samples... 

Both the value of the intrinsic viscosity and virial coefficients of the concentration dependence terms decrease with time. The reduced specific viscosity... 

The viscosity behavior of poly[(a-carboxymethyl)ethyl isocyanide] may be studied in neutral organic solvents. The concentration dependence of its reduced specific viscosity in 1,2-dichloroethane is shown in Fig. 11. A linear dependence indicates that the coefficients of higher concentration terms of the usual virial equations are negligibly small—a case which should be found with molecules, such as stiff rods, that give few intermolecular entanglements in dilute solution. 

Fig. 8. Poly-y-benzyl-L-glutamates from polymerizations in dioxane solution with n-hexyiamine initiator, A with sodium hydroxide initiator, B degree of polymerization (D. P.) as a function of anhydride-initiator ratio (A/X). The molecular weights were obtained from reduced specific viscosities at concentrations of 0.2% in dichloroacetic acid. [Reprinted from paper by E. R. Blout and R. H Karlson J. Am. Chero. Soc. 78...

Figure 4.2. Determination of intrinsic viscosity. Intrinsic viscosity is determined by extrapolation of the reduced specific viscosity (r sr) to zero concentration. The reduced specific viscosity is calculated by taking the difference between the flow time in a capillary for polymer in a solvent and that of the pure solvent and dividing the difference by the flow time of the pure solvent times the polymer weight concentration. Data are shown for hyaluronan for various fractions isolated from bovine vitreous.

Table I illustrates the structures of the modified polyarylethers, their glass-transition temperatures, and their reduced specific viscosities (RV) measured in chloroform at 25°C at a concentration of 0.2 g/100 mL.

Fig. 51.—Reduced specific viscosity of 0.93% starch solution as a function of concentration of sodium dodecylsulfate. (Reprinted with permission from S. Saito, Kolloid-Z., 154 (1957) 19-29.)...

To recover the polymer, latex samples were coagulated in absolute alcohol, filtered, washed with absolute alcohol, and dried under vacuum at 35° C. The polymer molecular weights were estimated from the reduced specific viscosities (0.400 gram of polymer per 100 cu. cm. of aqueous 0.5N NaCl solution, at 30° C.) according to the relationship of Vanderkooi, Schultz, and SieglaflF (42). 

Fig. 5. Reduced specific viscosity of a copolymer containing mole fractions of 36% HEMA and 64% MAA, normalized to value at alpha = 1 at high pH, plotted as a function of alpha. Also as a function of alpha derivative of normalized viscosity and apparent pKa of the polymer...

Fig. 6. Normalized reduced specific viscosities as a function of pH Polymethacrylic acid (PMAA open squares), polydimethylaminoethyl methacrylate (PDMAEMA open triangles) and a polyampholye containing mole fractions of 26% MAA, 30% DMAEMA, and 44% HEMA (open circles)...

The reduced specific viscosities of GDH in solution with 10" M GTP and 10 M NADH have been measured, and a value of intrinsic viscosity of [17] = 3.2 ml/g obtained by extrapolation to zero protein concentration (107). The transverse and axial rotary frictional coefficients of macroscopic models, similar to the physical model depicted in Fig. 2, were measured, and the viscosity calculated from these coefficients agrees with the measured value however, it is not possible to define whether the subunits adopt a staggered or eclipsed conformation, as viewed down the threefold axis, and other models may give the same result. 

This quantity, however, has a contribution from the intermolecular interactions between the macromolecules. This contribution can be eliminated by extrapolating the reduced specific viscosity to infinite dilution, when we obtain what is known as the limiting viscosity number or as the intrinsic viscosity, which is given the symbol [rf ... 

Polymer Synthesis. All polymers were prepared in dimethylacetamide at the temperature of 85°C for 20 - 30 min in nitrogen atmosphere. Table I summarizes the reduced specific viscosity, density (p), and glass transition temperature (Tg)... 

Table I. Reduced Specific Viscosity ijiJC), Density (/9), and Glass Transition Temperature (Jg)...

Polymer solutions are never ideal since dissolved macromolecules influence each other even at very low concentration. On the other hand, a reliable correlation of solution viscosity and molecular weight is only possible if the dissolved macromolecules are not affected by mutual interactions they must be actually independent of each other. Therefore, the viscosity of polymer solutions should be determined at infinite dilution. However, such measurements are impossible in practice. So one works at an as low as possible polymer concentration and extrapolates the obtained values to zero concentration. To do so, the elution time measurements are not only carried out for one single polymer concentration but for varying polymer concentrations (e.g., 10, 5, 2.5, 1.25 g/1). For each solution, the value of the reduced specific viscosity is figured out (the data will make evident that this quantity is clearly concentration-dependent even at the lowest possible polymer... 

Fig.2 Reduced specific viscosities of PEO solutions in distilled water versus the shear rate — calculated from a dimerization process. -——Experimental c = 60 ppm c = 100 ppm.

Reduced specific viscosity dependent on the concentration of PAAn in water at 25°C. day in solution... 

An example of the time dependence of the reduced specific viscosity is... 

A typical example of reduced specific viscosity dependent on time at 25 C in H2O. 

Viscosimetric determinations. The Newtonian intrinsic viscosity of the xanthan molecule was determined by measuring the viscosities of several dilute polymer solutions with a Contraves Low-Shear viscometer. Extrapolation at zero polymer concentration of the reduced specific viscosity gave the value of the intrinsic viscosity, and the Huggins constant was calculated from the slope of the curve. 

The full-scale test were performed to find the influence of reaction time, solvent nature, temperature, and reagents feed ration on intrinsic viscosity of polyarylate oximates to find out the optimal reaction conditions for their preparation in accordance with the Scheme 1. It was found that synthesis of polyarylate oximates can be carried out more efficiently in dioxane at 303 K during 40 min. with triethylamine as catalyst and molar ratio DKO/ (CAT) / (DCAIP) = 2/1/1. The reduced specific viscosity r red for a resulting polyarylate oximate was within the range of 0.71-0.81 dl/g. It should be noted that synthesis of polyarylate oximates from phenyl ketoximes in acetone as a solvent proceeded as a heterogeneous proeess and the resulting polymer precipitated from a solution. 

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