I'm doing TEMPO oxidized cellulose nanofiber (TOCN) research. Based on most of the paper I read, after the reaction, the TOCN is washed by water and stored in suspension phase. I don't know why they don't dry the sample in the oven. First, I guess during the drying process nano cellulose will agglomerate due to hydrogen bonding interaction, and this bonding causes TOCN can't re-disperse in the water. But when I tried drying TOCN, I still can re-disperse it in the water. Is there anyone can explain to me? Thank you very much.
Of course that you can re-disperse it in the water, but in the drying process the fiber will be agglomerate due to the formation of irreversible hydrogen bonds and it will affect the nano scale size of your nanocellulose. So the nanofibrillar cellulose that you re-disperse will be not the same that you get in the first time.
Tempo-oxidized nanocellulose TOCN can be oven-dried (rigid foamed layer), spray dried (small particles) or freeze-dried (flexible foam), but all these methods affect the nano scale size. One possibility would be to substitute the water by methanol or isopropanol completely in several washing steps, then membrane filtration and vaccum drying to receive alcohole content less than 5 ppm (cost-intensive and time consuming). If you can accept coarser particles and CMC content, you should switch to colloidal microcrystalline systems like VIVAPUR MCG.
It is possible, if the chemistry is right. Preferably the fibrils should have high charge (being in the deprotonated form) and for TEMPO there should not be any remaining aldehydes. Two suitable references:
Takaichi, S.; Saito, T.; Tanaka, R.; Isogai, A., Improvement of nanodispersibility of oven-dried TEMPO-oxidized celluloses in water. Cellulose 2014, 21 (6), 4093-4103
Butchosa, N.; Zhou, Q., Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose. Cellulose 2014, 21 (6), 4349-4358.
Yes, you can re-disperse oven-dried nanocellulose in water. However, the morphological properties of the dried nanocelluloses are dependent on the particular drying method, feedstock materials to make nanocelluloses, etc. The aggregates/agglomerates generated during the drying can result high off-specification nanocelluloses and cause difficulty for the re-dispersion of them in water. Due to strong hydrogen bonding between them, breaking down the aggregations/agglomerates is an energy consumption process.
Other drying methods rather than oven-dry could provide you a better chance to re-disperse nanocelluloses in water.
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