Dear colleagues and professors.
I use raft polymerization to get new polymer based on the methacryalte version
I used ACVA and trithiocarbonate as CTA and my solvent is methanol. I used 70 C for the reaction.
I also degassed using the freeze-pump-thaw cycles for several times.
However, after 16 h of polymerization, i obtained the product with degree of polymerization of only =3 while my target DP=90
What could be the reason for that knowing that my polymer will form micelle structure.
Also, how can the increase the MWt?
Thanks for help.
Based on reaction conditions you mentioned here, I would first change the solvent to DMF, DMAc or Anisol. Methanol is not a good solvent for RAFT polymerization. You are using methanol (BP 65oC) to do a reaction at 70oC. Second, you haven't described anything about monomer and chain transfer agent. So, my guess is you have to play with substituent groups on the trithiocarbonate to get the best results. And if the degree of polymerization is 3, that means it is not polymerizing at all, it's just an oligomer. ( I am not sure how did you calculate the DP). You haven't mentioned the conversion either. IF DP is only 3, then one of the reason could be your CTA is transferring very quickly. In that case you can change the monomer to CTA ratio.
Dear avichal Vaish
Thank you for your suggestion.
My monomer is new phospholipid monomer based on the methaclate version of chloine phosphate. My CTA is 2-cyano-2- propyl dodecyl trithiocarbonate.
used gpc to measure the mwt , it is only 1175 after 16 h.
My monomer mwt is 450, that isDP=3
Any suggestions?
This will help you. I think, this is similar to your work. In that case you have to change the CTA. Check the supporting info.
Article Functional Choline Phosphate Polymers
Another thing what kind of GPC you are using? If conventional THF GPC, then its not gonna work. Because your polymer will form aggregate which will give less "apparent" molecular weight. In this paper they used TFE GPC with PMMA standards.
So first of all the GPC with PEO standard is not even close to your polymer. Please refer to the convertion you can obtain from NMR as I expect the determination of your conversion with gc is not possible. anisole could be a good standard for your polymerization system. The Iinitiator has to be changed as well due to solubility if you change to dmf. Furthermore. You should polimerize in a solvent that is preventing your polymer from micellization to obtain good results in DP.
Good Luck
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