Our project partner asked me to measure the pH-dependent swelling of chitosan layers. Those layers were prepared by just drying dissolved chitosan in acidic acid. For comparison purpose I tried to find a publication which illustrates a depedency. I did not find one with Chitosan prepared that way. And moreover I did not find any evidence of pH-dependency for pH>6.5. Does anyone have some information for me?
Hi,
I have been working quite a while with chitosan and examining the pH dependence of its mixtures with oppositely charged surfactants. By pH titration (published in Langmuir 2014, 30, 1778–1787.) we see that the degree of protonation of chitosan (with DA = 0.16) at pH 6.5 is still 0.3, and for full deprotonation you need to reach a pH of ca. 8. Hope this helps.
Viele Grüße,
Leonardo
Dear Leonardo,
thank you very much for your answer. At least one! I am not a chemist, so it was hard for me to work through all the literature. What I found out based on (Schulz et al., Technisches Messen 2010) was that the pKb, the point were protonation starts, plays a decisive role. It is around 7.5, calculated from pKa. So, below 7,5 there should be a swelling observable, right? I hope it is not too trivial for the readership!
Beste Grüße
Anna
Hi, this is very good question, the pure chitosan is stable in higher pH, but increasing the protonation characters.
Well, yes, below pH 7.5 you should observe protonation of chitosan. However, I would be cautious before saying that below pH 7.5 you observe swelling. Chitosan is a very strange guy, and the only way to get a certain answer is to carry out an experiment.
Greets,
Leonardo
I will do so. I expect that the swelling is very little, in the range of some % and maybe hardly to measure. I hope I have luck with the strange guy. Thanks again!
Prakash, do you mean above 7.5?
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