I wanted to synthesize some polymer of a particular Mn, but when I characterized it with GPC, I found there were two peaks which overlapped with each other. I heard there is a method called fractional precipitation which separates such polymers with two similar Mn. Does anyone know how this is done? Thanks.
Following article will be helpful
http://onlinelibrary.wiley.com/doi/10.1002/pol.1981.170190215/abstract
http://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_mathematik_und_naturwissenschaften/fachrichtung_chemie/pcp/lehre/vorlesungen/download/pcp_polymercharakterisierung/Charakterisierung_BSc_eng.pdf
Dear all;
this is a very old and classical way to find the molecular weight distribution of a given polymer providing the existance of a couples of solvents/non-solvents. There are a pleinty of data on this topic. Dr. Nizar Matar is among those scientists in RG who has a practical experience with this matter, I hope he will contribute to this question. I have some papers, if you specify more the polymer you are dealing with may be I can help you with some of them. Regards
Dear Wang,
If you are thinking of a change in your synthesis method, i could offer you a technique which will help you to contrast your DP. Frankly speaking, this type of processes (fractionation) are very expensive which will produce obstacles in the application part. So, if you could give us more details. It would be easier to contribute to the solution. Within this lack of informationi it is very hard to offer an exact option. In this step ı will just advice you to look forward to Flory–Huggins solution theory. If there is enough difference on their Partition coefficient, they may be separated via a contrasting the solution composition and temperature.
Good luck.
Dear all;
in my previous answer I was limited by the scope of the question. Now, if you have other options, I think the best one will beto synthesise your polymer via a living/controlled polymerization technique (NMP, ATRP, and RAFT/MADIX), and you optimize for the needed Mn. Regards
if possibale, you can use a solvent to make one component soluted firstly at a selected temperature, and then another one. After several cycles, you maybe can separate the one from each other.
To fractionate polymers, a number of methods described in the literature have been used for semi-crystalline polymers. These methods include solvent-extraction, consecutive extraction with different solvents, fractionation with solvent/non-solvent pairs, consecutive extraction with a solvent at different temperatures, and more recently TREF. TREF is based on the hypothesis that the crystallization from solution of a polymer is dependent on the crystallizability of the dissolved polymer at a certain temperature. The main disadvantage of TREF is that the apparatus requires complex instrumentation and that it is expensive.
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