After I prepare the agarose hydrogel, I store them in PBS for 24h, then weigh them. Let this weight be called W0. Then I let the hydrogel dry for about 20h. Then, I put the hydrogel for another 24h. I obtain this weight. Let this weight be W1. What I found is that W1
Hydrogel consist of 90% of water(10% polymer chain), when it is subjected to drying the water is removed from the substrate leading to the loss of water. The loss of weight corresponds to the water molecules entrapped in the hydro gel 3D self assembly.
Thank you, Berwin Singh for your reply. Actually, I am more interested in knowing why the hydrogel ,during the process of reswelling, did not swell to its initial swollen weight.
For high water content the hydrogel would be dried close to wet-bulb temperature of the air stream contacting the gel, and eventually, after attaining much lower moisture content, the drying gel temperature should increase to about the dry-bulb temperature of the air stream. In principle, the equilibrium water vapour pressure above the gel is higher than water partial pressure in air, this meaning that that chemical equilibrium is not reached between the gel and the air stream. That provides the 'driving force' for mass transfer. As long as the air dry-bulb temperature is not too high ― so that no phase transition or irreversible chemical change could occur ― re-hydration of the hydrogel can be promoted. By contacting previously dried gel with saturated air at room (dry-bulb) temperature, the gel should uptake moisture from the air stream. However, we often can expect some hysteresis on a cycle type process, even if chemical equilibrium between the gel and the air could be practically attained, this meaning that the gel thermal history may possibly also contribute to the final moisture content of the gel. Also notice that the initial/final gel moisture content may be far from equilibrium with the laboratory atmosphere.
this is simple after once hydration then drying the polymers get crystalise like rice grain once swell in water then dried it after that if try to swell again its can not possible due to crystallization of polysaccharide.This type of phenomenon may take place in your gel polymers
You can find some information in this paper:-
Clarke, B. L. (1925), Studies in Swelling: The swelling of agar-agar as a function of water content before swelling
Dear Ram,
I think hydrolytic degradation could be a reason during water uptake.
Regards
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