I have determined the intrinsic viscosity (η, L/Kg) of eucalyptus kraft pulps from different bleaching stages, by the cupriethylendiamine method.
According to Henriksson et al. (2008) the relation between degree of polymerization (DP) and molecular weight is given by: η = 0.42 DP for DP < 950 and η = 2.28 DP^0.76 for DP > 950
At this point, I still don't know the DP of the pulp (still waiting for the gel permeation chromatography results), reason why I don't know how to proceed with the calculation.
By applying the Mark-Houwink equation, [η] = KMα, I'm not aware of the K and α values for my polymer solvent system... How can I get these constants values?
Many thanks in advance =)
Dear Colleague, Without establishing the Kuhn-Mark-Houwink constants the viscosity data can be used only for comparison.
The Mark-Houwink-Sakurada equation is only empirical. Thus, the constants, K and a, are determined only when you have multiple samples of known intrinsic viscosity and molecular weight, which was determined by the absolute molecular weight determination technique, such as light scattering, or osmotic pressure. By the way, in your description, [η] = KMα, the constant a should be power of M, thus the correct equation should be [η] = KM**α. If you do not have K and a values, as Dr. Banhegyi said, you can only compare relative molecular size since K and a are constants for the particular polymer. If you have need of determining the viscosity average molecular weight using Mark-Houwink-Sakurada equation for many samples, I suggest that you do absolute molecular weight determination by light scattering and draw a calibration curve from which K and a constants can be determined. From then, you can determine the viscosity average molecular weight of any samples as long as the material is the same and you know the intrinsic viscosity.
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