Liophilization alone might not be enough. We have tried succesfully first quenching in N2 and then liophilization.
Hope this helps.
There are typically three methods of making aerogels. The post popular, but involved method is supercritical drying using CO2. This method has the disadvantage of expense device and the size limitation, though it minimizes the effect of surface tension related shrinkage. The less involved method is the freeze drying. Since this method is popular in food industry, a large instrument is available and much less expensive. For this, you first freeze it either in liquid nitrogen or dry ice/solvent mixture and drying it without thawing (liofilization). The last and the easiest method is the ambient drying without using any device mentioned above. This method is the easiest, but the polymer used to make the gel must have high strength when it is made into the gel. so that it does not collapse by the surface tension wile drying Thus, it is not applicable for all the polymers. To my knowledge, only polybenzoxazines have been reported to be successful. Condition of freezing (the morphology of ice crystals) strongly influences the pore shape, size and its distribution, and morphology.
The most effective method is by utilizing a supercritical drying phase with CO2 and a high pressure autoclave. Your autoclave will need to run at 1600 PSI for at least 72 hours to remove all of the ethanol/methanol.
I prepared an extremely porous aerogel via coupling and subsequent freeze-drying. Porosity was within the range of 99.7% and the mechanical properties were enough good. I recommend to dyalize the hydrogel prior to freeze-drying. Read this publication, it could be useful. Best wishes!
Article Synthesis and self-assembly of a PEGylated-graphene aerogel
If cellulose hydrogels must be freeze before freeze dryer for aerogel preparation?
- Badges
- Science topic
- Similar topics
- Biological Science
- Biochemistry
- Enzymology
- Enzymes