In our laboratory we synthesized a new polymer by adding some molecules as branches on the base polymer chain. The molecular weight of the base polymer chain and molecules which were added are known.
One option is to get the SEC of each, base and syntesized polymers. Other is (if enough sample is available) is to get the viscosity and use the Flory-Huggins equations. It may be better to know what method was used on the base polymer and branches and perform the same. Good Luck!!!
High pressure size exclusion chromatography (HP-SEC) with multi angle laser light (MALS) detector is a very good method form measuring absolute molecular weight of polymers.
Size Exclusion Chromatography is also called Gel Permeation Chromatography when an organic solvent is used as a mobile phase.
If you do not have this instrument, then you either measure the average molecular weight by osmotic pressure or by freezing point depression. You can have an idea about the approximate M.Wt. by viscosity measurement. Approximate because the exact values of the 2 constants (K & a) in Mark–Houwink–Sakurada equation [ which relates M.Wt. with intrinsic viscosity] are not available for your new polymer.
such GPC can only be applied if the polymer is TRUELY soluble in the solvent used, in the same solvent as MW standards.
Dear Hossein u can do GPC (Gel Permeation Chroma.) , it also depends on your polymer you can analyze its weight by NMR, viscometry and many other methods are also available. I think the best way is doing GPC measurements.
Thank you all.
Dear Shashank, I think at first need to do NMR because I should measure the number of branches which attached to the main polymer chain. then do GPC to measure polymeric MW. But do I need to do other experiment or just can find MW by GPC?
Since you want to carry out GPC , follow the valuable advice of Professor Bernhard Wessling & be sure that your polymer is truly soluble in the solvent used. The advice also applies to measuring the M.Wt. by viscosity or by freezing point depression.
Dear Hossein i think GPC is a good measurement for calculating MW of polymers and u do not need to do any other thing after that but u can do some other measurements in order to get MW. If you are interested then i can mail you some of my papers where i have done MW measurements by NMR, and also some equations are available from which you can do theoretical MW measurements.
Dear Shashank
Thank you for your kind help.
It would be my pleasure if you send me your papers.
My email address is: [email protected]
GPC is probably the best tool for your project. Advanced GPC detection (light scattering for molecular weight and intrinsic viscosity for structural insights) can be done if your sample is well-dissolved in the mobile phase.
To gain a quick understanding of the size of your polymer and whether it is aggregated or not, dynamic light scattering may also be quite useful.
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