Currently, I'm preparation a homopolymer sodium salt using Sodium Persulfate as initiator and sodium hydpophospoite as CTA. But,my polymer that I've got have high molecular weight. I need your advise how to decrease my polymer molecular weight besides add more volume of water in the initial of the reaction (before polymerization) because I know homopolymer is a solution polymerization so I think they need more solvent so that the molecular weight is lower than before
Dear all, there are many possibilities to get the required MW. If you have the kinetics curve of the polymerization reaction, i. e., MW vs time or MW vs %conversion, then all to do is to quench the reaction at the time or % conversion corresponding to the targeted MW. The second solution is to do dialysis fractionation with a memebrane with the specific MW cut-off. The third possibility is to do mechanical degradation by shearing either by high speed agitator or passing through low porosity sieves.
If you want to avoid these extra work, choose a solvent with high transfer constant, and reduce the polymerization temperature. Starve feeding of the monomer may also help to reach a moderate MW. My Regards
Totally agree with Mr. Bouaziz.
In addition would like to mention an option of using a chain stopper additive.
Btw, how do you control your reaction?
Please check the following free access RG document.
https://www.researchgate.net/publication/309033992_THE_SYNTHESIS_OF_POLYACRYLIC_ACID_WITH_CONTROLLED_MOLECULAR_WEIGHTS
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