I measured the pH of pure polymers and it was different from 7.0. And I ask: is there some residual pH due to its production process? Due to its water content? I'd like an explanation for that... and some references.
The biggest single source comes from the initiator utilized for polymerization. The initiator has its own chemical pathway as side reactions from the desired initiation of polymerization. In addition, it may itself be either acidic or basic in nature. For example, persulfate would be strongly acidic, while various cationic initiators would be basic in character. In short, you need to peruse the actual recipe for the polymer you are interested in, to determine the sources of the behavior you observed.
Many water soluble polymers are either acidic (polyacrylic acid) or basic (polyethylene imine). When you dissolve them in water, you will measure pH values below or above 7. of course, it depends on their chemical structures.
Daniel,
do you have some article to propose me to read? Something that I can use in a "literature cited" section of my article?
Thank you!
Actually about the acidic or basic polymers, you can find a lot of nice reviews in the literature. Maybe you can start from one of such reviews (for example pH-Responsive polymers: synthesis, properties and applications, Soft Matter, 2008,4, 435-449, or Stimuli-reponsive polymers and their bioconjugates, Prog. Polym. Sci, 2004, 29, 1173-1222) and find papers focused more on your interest.
I believe you got your reply. Carboxylic acid, sulphonic acid, phosphonic acid, amines etc attached to a polymers can give pH different from 7.0. Check with pH sensitive polymers. Most important is to purify the polymer after synthesis.
What pure polymer do you investigate? Is it polyelectrolyte or neutral polymer? Besides, did you measure pH of pure water? The presence of neutral low molecular weight salts shift pH also.
Hi
it's depend on polymer functional groups and end groups of it. if you have a COOH as a pendant or end groups, the pH value is below 7.0 and if you have some groups that they act as a alkaline groups, the pH is above 7.0.
it's very clear, and you don't need to refer to any document
Dear Leo
please check the distilled water pH value, i checked it in 3 or 4 lab,, and all of them show pH value about 5.5!!!
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