I was working with a methacrylated gelatin hydrogel that was cross linked by UV exposure. After cross linking, I put the gel for a few hours and I noticed that It got dehydrated and I got a thin film(not flat) in the bottom. Wasn't the hydrogel supposed to maintain its dimensions when water leaves the pores because it is cross linked?
Dear Rizwan Muhammad, have you confiremed the UV crosslinking?, wehter the crosslinking takes place or not, in general the gelatine solution when under go cooling it gets gel nature for appearence, but its not a gel. so first confirm the UV crosslining is takes palece or not with this polymer and monomes and then proceed so that you can get nice gel.and finally check methacrelation of geltin also.............
Hi Rizwan, in general all hydrogel lose some volume after drying at room temperature. This is more obvious in nature based hydrogels, which are mecanically speaking less stable and they will complete collapse IF the crosslinking degree is small. You can increase the degree of crosslinking, just for a try, but I would rather choose another technique to dry this hydrogel (e.g. Freeze-drying).
As water which penetrated into crosslinked network of hydrogel leaves when gel gets dried, gel will lose its original form and shrink into a form which could look quite different from original hydrogel shape...based on my experience
The final shape after dehydration will depend on your polymer concentration and the strength of the polymer you use. Usually, the concentration of polymer is low in the hydrogels, and the polymer chains are soft. The hydrogel elasticity comes from the resistance of polymers to stretching, but not the compression. During the process of dehydration, the polymer network would collapse due to the compressive stress possibly from the surface tension of the liquid...
Depend on the crosslinkage. The shape may change a lot. but the chemical structure will keep. Focus on what you are looking for.
Whether the obtained gels maintain their 3-D shape or collapse at an elevated temperature, it depends on several factors. Degree of crossliking, flexibility (rigidity) of the polymer chains, and interaction between the solvent molecules and polymer network are the first three preffered factors.
Dear all, Thank for your valuable inputs. My gel was definitely cross-linked (highly). I didn't want to dehydrate it intentionally. It just got dehydrated unintentionally. If I were to go for dehydration, I'd prefer freeze drying to maintain shape. So only accidentally I found that my gel didn't maintain its shape.
The answer from Qi Wen seems logical. It could be the surface tension that will pull the chains down as water evaporates due to its surface tension.
@David: I think solvent exchange will take very very long time. Imagine that the CO2 needs to replace the water that is in the pores not just on the surface but in the 3D structure. Just an opinion. If someone has actually done critical point drying of hydrogel, please let us know also along with the hydrogel thickness.
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