Thermal and viscoelastic properties of cellulosic gels with different ionic liquids and coagulation agents
Journal article, 2013
Thermal and viscoelastic properties of three-component gels consisting of microcrystalline cellulose, ionic liquid, and coagulation agent were studied. The amount and type of components was varied to obtain different gel properties. The absorption of coagulation agent (13 to 35 %wt of water or ethanol) was found to depend on the types of ionic liquid and cellulose. Surface hydrophobization of cellulose prior to preparation of the gel remarkably resulted in the gels containing the most coagulation agent (35%wt). Rheological studies indicated a linear viscoelastic behavior in storage modulus but not in loss modulus, which is a behavior that, according to our knowledge, has not been seen before for gels. Increasing the cellulose concentration from 1:20 to 1:10 increased the stiffness of the gels. The highest critical stress value (1050 Pa) was obtained for a gel containing 1-butyl-3-methylimidazolium chloride and water. Finally, it was confirmed by dynamic-mechanical experiments that the gels had a cross-linked structure.
Differential scanning calorimetry