한양대학교 Nano Bio Tech Lab.

The swelling behavior of chitosan hydrogels in ionic liquid-water binary systems was studied using hydrophilic
room-temperature ionic liquids (RTILs) to elucidate the swelling mechanism of chitosan hydrogels. No penetration
of RTIL into a dry chitosan material was observed. Swelling was achieved by soaking in water-RTIL binary mixtures,
with larger swelling observed at higher water contents. In one instance, the binary mixture was acidic and produced
larger than expected swelling due to the dissociation of the amine groups in the chitosan. The equilibrium binary system
content behavior of the chitosan hydrogels depended upon the amount of free water, which is a measure of the number
of water molecules that do not interact with the ionic liquid. After evaporation of water, remnant RTIL remained in
the chitosan network and hardness testing indicated a plasticization effect, suggesting that the RTIL molecularly mixed
with the chitosan. Chitosan hydrogels containing only RTIL were prepared by dropping pure RTIL onto a fully
preswollen hydrogel followed by water evaporation. This method may be a useful means for preparing air-stable
swollen chitosan gels.