Good day. I have been trying to synthesize PVA hydrogels through cyclic freeze thawing but unfortunately, only a viscous liquid is formed even after several cycles. To provide more details, I am currently preparing a 12w/v polyvinyl alcohol solution. I am using USP grade with 85-89% hydrolysis. This solution is magnetically stirred and heated at 80-90 degrees celsius for 4 hours followed by casting in a plastic petri dish. The petri dish is then frozen inside a refrigerator freezer (-17 degrees celsius, measured with a thermostat) for 18 h followed by thawing for 6 h. This is repeated for three cycles. However, no hydrogels form even at the third cycle.
Some problems I have encountered is mostly on the PVA solution preparation, wherein some of the PVA sticks to the bottom of the beaker. I have tried several methods of dissolving the PVA, such as dissolving it first at low temperature then slowly heating it to the desired temperature. I have also tried heating the water first then placing the PVA. In both cases, dissolution of PVA has not been successful and there is a lot of water loss due to evaporation. Can this be a factor why the hydrogels fail to form? Also, is the refrigerator freezer set up enough for freeze thawing? Thank you so much. I hope you can help me improve my methods.
Dear all;
I think the molecular weight is not the appropriate one. To be more realistic I suggest to use a higher molecular weight with a high degree of hydrolysis. Regards
Dear Ruth Naomi Mariae Rosales;
my hope is that the attached fles will bring the necessary help. Regards
Please try PVAL from Sigma-Aldrich - having an average molecular weight from 85,000-124,000 and 99+% degree of hydrolysis
It is very easy to prepare a hydrogel from PVA as well as dry PVA film.
1. Use X grams of PVA in 100 ml of water.
2. Use a hot plate with a magnetic stirrer for proper mixing.
3. Maintain the temperature at 100-degree centigrade.
4. Keep speed at 3000 rpm.
5. Wait for 2 hours.
6. A number of freeze-thaw cycles 30 gives better results.
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