How can I determine the molecular weight of a polysaccharide (as a powder) dependng on the viscosity?
one can find the answer here https://www.nottingham.ac.uk/ncmh/documents/papers/paper82.pdf
Determining the molecular weight of a polysaccharide based solely on viscosity measurements can be challenging because viscosity depends on various factors such as concentration, temperature, and the polysaccharide's conformation and interactions with solvent molecules.
However, there are methods that utilize viscosity measurements in conjunction with other techniques to estimate molecular weight. One common approach is to use Mark-Houwink-Sakurada (MHS) equations, which correlate the intrinsic viscosity of a polymer solution with its molecular weight. The MHS equation is often expressed as:
\[ [η] = KM^a \]
Where:
- [η] is the intrinsic viscosity,
- M is the molecular weight,
- K and a are constants that depend on the polymer-solvent system and temperature.
By measuring the intrinsic viscosity of the polysaccharide solution at different concentrations and plotting [η] versus concentration, you can determine the value of the constant "a". Then, by knowing the value of "a" and measuring [η] at a particular concentration, you can estimate the molecular weight "M" using the MHS equation.
Keep in mind that this method provides an estimate rather than an exact measurement of molecular weight, and it's important to validate the results using other techniques such as gel permeation chromatography (GPC) or light scattering methods for more accurate molecular weight determination.
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