You just need to dissolve the material in a minimal amount of solvent (methylene chloride) and add to a non-solvent like methanol in excess to remove the small molecular weight monomers, oligomers, etc.  Quantitation is more difficult but you could then do standard HPLC on the solvent mixture after removing the polymer by filtration.

Simply drop the common solution of polymer and low molecular weight substrate into a 10 fold excess of a non solvent of the polymer which is solvent for the substrate.

Dr. Ritter, I appreciate your answer.  Would you please provide some details about the column materials and elution solvent etc. -B. Loganathan.

You just need to dissolve the material in a minimal amount of solvent (methylene chloride) and add to a non-solvent like methanol in excess to remove the small molecular weight monomers, oligomers, etc.  Quantitation is more difficult but you could then do standard HPLC on the solvent mixture after removing the polymer by filtration.

Dr. Dalton, Thank you.    The technique you suggested will remove all low Mwt residual monomers?  Any suggestion for filtration - what type of filter is appropriate?  -B. Loganathan

Dear all,

in addition to precipitation in a nonsolvent, membrane dialysis may also be another option. Just use a membrane with the appropriate molecular weight cut-off. Regards

all the above provide feasible solutions to your answer. both precipitation and dialysis are OK

Most filter papers should work depending on the molecular weight and the nature of the precipitate.  If it is very fine you need to go to a finer or smaller pore size filter paper otherwise about anything should work.  Also, the process can be repeated multiple times.

A separate extraction/precipitation step can be problematic if the monomers or other low mw material is significantly soluble in the polymer mass.

An entirely different approach is to do regular hplc using a porous microsphere packing.  It will exclude the polymer at the solvent front (actuually before it) and then do regular  high sensitivity detection HPLC on the retained components. 

Thank you Dr. Abbott.  I appreciate your answer.  Would you mind providing me with some details regarding the porous microsphere column and suitable solvent system, ~ flow rate, and conditions I should try.  Thanks again. 

You can use those centrifugal filters with different cut-offs. So, if you use the 10kDa MWCO centrifugal filter than you will get only the polymers with MW above this limit.

But generally I would use the above mentioned precipitation procedure (1:10 solvent:non-solvent) as mentioned by Prof. Ritter. 

There are many suggestions while precipitation and membrane dialysis will give you the desired result. I want to add more. You must know whether your monomer and polymer are soluble in same solvent. In membrane dialysis no need to know. In precipitation you must take non-solvent in which your polymer does not dissolve. If so in this method, you have to use non-solvent combination, chilled non-solvent etc. You have to repeat solution/precipitation 2-3 times to remove monomer completely.

In addition to the previous answer, in order to improve the precipitation process and to make it faster, you can associate centrifugation (10000 r/min). The supernatant'll be enrich of the monomer fraction.

It is better if you give exact names of  residual monomers since you mention that the concantration levels of these monomer is in ppb range. Simple methods for determination of the monomers may not work in this case.

Dear/Sir

you can separate  the unreacted monomers than polymer by add ethanol(95%) to the mixture ,then filter the solution , the filtrate is unreacted monomer

In addition to the previous answers, after centrifugation or precipitation you can try Static Light Scatering or Dynamic Light Scatering analyses, by which you can determine the molecular weight of the purified polymer. HPLC would be a good analysis to see the fractions of your polymer.

I think centrifugation would be useful and also dialysis membrane too. Afterwards you can dosate the epoxy groups of both fractions: polymer and unreacted monomers (they do not contain the epoxy groups, as you mentioned) and verify if your saparation was well done.

To do the prep with GPC, just use a column based on porous silica microspheres. Depending on the amount of purified material needed, choose the column geometry appropriately and consequent flow rates. You will be surprised that the capacity for separation is much larger than traditional hplc because the separation all occurs before the solvent front. With porous silica microsphere based sec columns, they can withstand large pressure drops without loss of resolution. As it happens, many manufacturers of prep columns choose porous supports. You might try a few and see if they have a fairly small pore size. Size exclusion effect occurs with any column having porous or even slightly porous particles. (That is why, in interactive chromatography under some conditions,, some samples give a peak before the solvent front). That peak is excluded material.

As mentioned earlier, both precipitation in large excess of non-solvent or most importantly, by dialysis, low mol. wt component can be isolated. GPC is also O.K. provided you have right combination of columns. Small molecules will elute fast and polymer molecules last. From calibration using monomers and polymers the oligomer elution position can be roughly predicted.

By dissolve the mixture in methanol . The monomer dissolves in methanol and Polymer not dissolve

Go for soxhlet extraction

you can try with Amicon® Ultra Centrifugal Filters with MW cutoff 3kDa to remove the low molecular weight monomers. This is a simple centrifuge technique. You can also try dialysis technique with a proper MW cutoff membrane.

Use a Wiped Film Evaporator. You can run the unit at shorter residence time and lower separation temperature as compared to traditional short path distillation unit.