Viscosity, dilute solution Huggins constant

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. 

A plot of q,p/C verses C is shown in Figure 5.2. Such plots are normally linear for dilute solutions. On extrapolating the curve to zero concentration, we get an intercept on the Y-axis. The value ofq /C at this dilution gives us the intrinsic viscosity of a solution, depicted by Iq). We also call it thehnuting viscosity number. The Huggins constant k in the equation (3) is obtained from the slope of the curve. The quantity r /C is sometimes called the reduced viscosity. 

Solution Viscosity. The intrinsic viscosities [77] of the copolymers were measured for solutions in dry toluene at 25 °C. by dilution in an Ubbelohde suspended-level viscometer. Conventional plots of rj/c (18) and log (1 + r )/c (29) were found to be nonlinear for all copolymers where 77 is the specific viscosity. To get accurate values of the intrinsic viscosities and of the Huggins constants h and k2, triple plots were drawn as recommended by Heller (16). These gave the intercept 1/[iy], and fci and were determined directly from the initial slopes of the plots... 

Eq. (16.2) can be used for predicting the viscosity of a dilute polymer solution if the Huggins constant kH is known. But literature values of kH or values predicted with Eq. (16.6) are rather inaccurate. So they do not permit a good prediction of rj. 

It was assumed that the solutions were Newtonian at the shear rates in the capillary. This assumption was assessed with Couette viscometer measurements of these dilute solutions over a range of shear rates and was reasonable. Deviations were found for solutions at the higher concentrations, as indicated by negative departure from linearity of the reduced-viscosity-concentration plots these values were not used for intrinsic viscosity and Huggins constant determination. 

Hydrophobic associations can dominate polymer conformation in solution and solution rheological properties. Intrinsic viscosity and Huggins interaction coefficients provided information on the conformation and intramolecular aggregation behavior of these polymers in dilute solution. The presence of hydrophobic associations caused a decrease in the intrinsic viscosity and an increase in the Huggins constant. These effects could be counterbalanced by increasing the ionic charge on the polymer through hydrolysis or by copolymerization with sodium acrylate. 

Addition to purified and diluted solutions of xanthan. For this study, it was necessary to prepare a non-aggregated xanthan solution which was obtained by extensive ultrafiltration of a commercial xanthan sample which was initially non-aggregated. The absence of aggregation was confirmed by the Huggins constant which was 0.4 and the intrinsic viscosity which was 6.7 m kg. This corresponds to a molecular weight of 4.8x10 daltons. This xanthan solution was adjusted at a polymer concentration of 0.4 g.l"l in a protein-rich solution such as com steep liquor (CSL). Before use, the com steep solution was centrifuged and only the clear supernatant was added to the xanthan solution. The solvent was 0.1 M sodium chloride and the ratio of protein to xanthan was 10% (w/w). 

Diluted solution Intrinsic viscosity (m3 kg-1) Huggins constant k ... 

See also Huggins equation and dilute-solution viscosity. Huggins constant, k, and Kraemer s, k, are related by k — k" = 0.5. Thus, since k is often between 0.6 and 0.8, k" will often lie between 0.1 and 0.3. Kamide K, Dobashi T (2000) Physical chemistry of polymer solutions. Elsevier, New York. Huggins ML (1958) Physical chemistry of high polymers. John Wiley and Sons Inc., New York. 

In viscosimetric measurements the product KnX[q] is a measure for the solvent quality that describes these additional interactions and the expansion of the coil by the solvent molecules (similar to the exponent a of the [/j]-M-relationship see The influence of the solvent quality on the [/j)-M-relationship in Chap. 6). Solely at theta-conditions the Huggins constant is zero and therefore the product KhX[/jP. At theta-conditions, the long-range interactions between polymer segments are compensated by the solvent even at higher concentrations (see Chap. 8). In this case, the specific viscosity /jgp of a dilute solution increases linearly with the concentration and the reduced viscosity is independent of the concentration and is equivalent to the intrinsic viscosity. 

The lattice theory of entropy of mixing, derived independently and contemporaneously by Huggins and Flory and the "Huggins constant K ", relating the concentration dependence of the viscosity of dilute polymer solutions are listed among Huggins major contributions to polymer science. He developed new procedures for more quantitative productions of solubiHty. 

S1 Schoff, C.K. Concentration dependence of the viscosity of dilute polymer solutions Huggins and Schulz-Blaschke constants. Polymer Handbook, Brandrap, J., Immergut, E.H., Gralke, E.A. (eds.), 4th Ed., p. VII/265-289, J. Wiley Sons, Inc., New York 1999... 

Dilute solution viscosities can provide additional infonnation on mechanochemistry. It has been suggested, for example, that the Huggins constant [38], from concentration dependence of solution viscosity, is dependent on chain branching [39]. This may be true, yet at best the effect is small. Moreover, this concept has not been tested for a range of polymers and branching. 

Concentration Dependence of the Viscosity of Dilute Polymer Solutions Huggins and Schulz-Blaschke Constants... 

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