I analyzed my polymer sample after polymerization by NMR and GPC. The Mn that I obtained by GPC didn't match with my conversion rate obtained by NMR.
For exemple, for a PEGMA RAFT polymerization I have an average Mn at 20852 and I calculated a conversion rate at 62%. My monomer molecular weight was 500 so, normally I have to have a molecular weight around 31000 for a conversion at 62 (62*500=31000). What is the problem?
Hi Mathilde. This is perfectly normal. The molecular weight obtained by SEC is not actually molecular weight. The SEC instrument 'sees' the hydrodynamic volume of your polymer and reports the molecular weight relative to the hydrodynamic volume of standards that were used to calibrate the instrument. So you will always get different results when you compare molecular weights obtained from NMR and SEC. Hope this helps.
Hi, thank you for your answer. So I can trust my NMR results and just keep my GPC results as information?
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