Branched polymers have much smaller hydrodynamic volume than the linear analogues with same molar mass, so molar mass can not be determined based on viscosity.
@karou and @gergely
Thanks for your reply. I have also made the same observation based on different literature. Is there any other method where we can use viscosity data to calculate the molar mass.
Fair warning, I am giving my best guess since I don't know all the details. If the main chain polymer is a well characterized polymer, then I would study it using well known Mark Houwink parameters from literature. Then, after grafting, I might look at the NMR spectrum of the product, and try to determine the main chain to grafted chain ratio, and estimate the molecular weight that way.
When using viscosity data, you either need literature data (Mark Houwink parameter of the exact linear polymer), or else make a calibration data set yourself using known molecular weight samples, which you do not have. So that is why I think you need a more absolute measurement technique like outlined above (i.e. NMR).
Dear Kaoru Aou,
if it is a two step synthesis than actually thats a great idea! Should work.
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