Can someone please help me! I'm having real trouble with Carother's equation and calculating the average degree of polymerisation (DP).
I have two different monomers - MonomerA and MonomerB. They react in a step-growth fashion, liberating HF.
MonomerA has four equivalent fluorines and, MonomerB has four equivalent OH's.
Therefore, I guess they can only polymerise in an alternating fashion
--> alternating copolymer (ideally, two HF's are liberated per MonomerA-MonomerB link)
Reacting MonomerA and MonomerB with 1:1 stoichiometry gives a polymer with average molecular weight = 90,000 (from GPC). The relative molecular weight of the repeating unit in the product is approx 460.
Now here's the problem:
Using Carother's eqn, I get DP = 391. I don't think this is right. Here's how I get my answer:
Mw = (DP x 460)/2 Therefore, DP = (90,000 x 2)/460 = 391.
I don't think I should be using '2'. As there are four 'active sites' per monomer, I can still get a MonomerA-MonomerB linkage when liberating just one HF), therefore, giving rise to an Alternating Graft Copolymer..?
Also, does 391 mean 391 MonomerA-MonomerB bonds or 391 sets of MonomerA and MonomerB per copolymer?
I definately know I'm going wrong somewhere but don't know where. Polymers have never really been my choice of study and, maths isn't quite for me either! Just doing a project at the moment so, if anyone can help, many thanks.