I am working with Polyacrylic acid (100.000Da) and instead of water, I need to use another solvent (dioxane) to dissolve PAA. However, because of the high molecular weight, it's quite hard to dissolve completely. I still see many small pieces of the polymer in the baker after 3-4 days even using sonication, thermal treatment, and stirring. So, does anyone have some tips or solutions for this problem?
Dear all, the concentration is not mentionned, may be it is too high ? I came across a paper where 127.000Da MW was soluble in dioxane. You can try a solvent with a base character (N-containing) and/or enhance the dissociation of the carboxylic acid groups in a suitable solvent and pH. My Regards
Hope the following references can help you in your research.
1) Phase behaviour of PAA in Dioxane has been studied by Cowie and Swinyard:
J.M.G. Cowie; B. Swinyard; “Location of three critical phase boundaries in poly(acrylic acid)-dioxane solutions”, Polymer 1990, Volume 31, Issue 8, Pages 1507-1513. doi.org/10.1016/0032-3861(90)90158-U
2) A similar question was asked in 2017, namely the dissolution of PAA in solvents other than water. I would look specifically at Dr Shavandi Amin's answer:
Shavandi, Amin. (2017). Re: Dissolution of polyacrylic acid(PAA)?. Retrieved from: https://www.researchgate.net/post/Dissolution-of-polyacrylic-acidPAA
Finally I would add that the use of mixed solvents is always a valid option, but it is necessary to carefully evaluate the mixture in the light of the recovery of the solvents.
Best regards
@Nguyen Thi Thuy Chau,
Why not use the lower molecular weight PAA instead? It is difficult to dissolve it for high molecular weight PAA. Mixed solvents as Niccolò Braidi suggested could get better solubility for PAA. You need to make a lot of effort to find ones.
Dear all, the concentration is not mentionned, may be it is too high ? I came across a paper where 127.000Da MW was soluble in dioxane. You can try a solvent with a base character (N-containing) and/or enhance the dissociation of the carboxylic acid groups in a suitable solvent and pH. My Regards
Hi;
Dissolving polyacrylic acid in water or an organic solvent is not always possible, especially when its molecular weight is high. It is well known that organic acids are all weak acids and therefore cannot dissolve in water. To increase the solubility of the acid it is necessary to convert it into its ionic form (salts) by adding a strong base. In addition, the pieces that remain at the bottom of the flask are gels (three-dimensional polymer network) which are also insoluble in water or organic solvents. A filtration operation may be required to separate the pieces from the solution.
With my best regards
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