GPC - MALLS and copolymers

[Karen01]

First I'm not sure this is question for this board... I don't think I've seen GPC as topic here .. and this question is more about detection/calculations rather than chromatography... If it's beyond the scope of the forum please let me know.


From what I've seen If one knows (or measures) the dn/dc of a homopolymer in the mobile phase, using MALLS coupled with a concentration detector (RI) you can determine the molecular weight distribution of polymer ...

What about with copolymers?

- Karen

[BHolmes]

At my last position I worked primarily with characterizing copolymers for a R&D group, specifically ones with complex structures (different degrees of branching, blocks, random, etc...). I was using a GPC with RI only, no MALLS, and I would analyze my unknown copolymer with several commercially available polymers and copolymers of different lengths, degress of branching, compositions, architecure, etc... BY comparing the elution order I was able to deduce what type of copolymer my unknown was. It was NOT exact, but with this information and that of other techniques (H & C NMR to determine actual structure, MALDI-MS for a molecular weight) I was enough to conclusively identify unique copolymers.

I hope this helps, I remember how frustrating copolymer characterization can be because two copolymers can have completely different compositions, structure, etc... but the same molecular volume and therefore similar retention times.

There are some great webinars available online, also a great resource is Polymer Standards Serice (PSS) they specialize in GPC and SEC analysis http://www.pssgpcshop.com