Study Of Dissolution And Rheology Of Collagen/Ionic Liquids Solutions

Protein is one of the richest renewable resources. Efficient utilization of collagen islimited because of the poor solubility of collagen in most common solvent. Ionic liquids （ILs）are green solvent, widely used in seperation, organic synthesis, material preparations andelectrochemistry due to their remarkable properties including strong polarity, nonvolatility,nonflammability and high thermal and chemical stability.In this paper, the ionic liquids choline chloride·xZnCl₂（x=1,2,3） were synthesized forthe purpose of dissolution of collagen. Then the solubility of collagen in ionic liquids, thechanges of original and regenerated collagen on the structure and properties, and the rheologyof collagen/ionic liquids solutions were investigated. Main contents of this thesis are asfollows:1. Preparation of ionic liquids choline chloride·xZnCl₂（x=1,2,3）, choline chloride andZnCl₂were taken as the main raw material. And the structure of the products wascharacterized. The results show that all the IR spectrum of ionic liquids cholinechloride·xZnCl₂（x=1,2,3） are exist the characteristic absorption peaks of the choline cation,so the chemical structure of ionic liquids choline chloride·xZnCl₂agree with their designedstructure.2. The solubility of collagen in choline chloride·2ZnCl₂was investigated. The resultsindicate that choline chloride·ZnCl₂ionic liquid has good solubility for collagen. In addition,the temperature has a strong effect on the solubility. The rate of dissolution increasedsignificantly with the increasing temperature. The solubility of collagen in the ionic liquidcholine chloride·2ZnCl₂can be achieved11.3g/100g at120℃.3. Regeneration and characterization of collagen from collagen/ionic liquid solution.The regenerated collagen was obtained from the collagen/ionic liquid solution by acetonitrile,which shows the ionic liquid choline chloride·2ZnCl₂is the direct solvent of collagen. Thenthe original collagen and regenerated samples were characterized by XRD, DSC techniquesrespectively, the results indicate that the regenerated collagen has lower crystallinity andthermostability.4. The rheological behaviors of the collagen/ionic liquid solutions were investigated. Inthe steady shear measurements, collagen/ionic liquids solution is a pseudoplastic fluid ofnon-Newtonian fluid. In the oscillatory shear measurements, both the storage modulus andloss modulus increased with the increasing frequency. In the low frequency region, thesolution mainly for the viscous fluid, and in the high frequency region, the elastic effect of the solution began to dominate. When the concentration increased, the storage modulus and lossmodulus both increased, the frequency of the solution from viscous flow change to elasticflow moves to the low frequency region, showing the pseudo-solid behavior; When thetemperature increased, the storage modulus and loss modulus both decreased, the frequencyof the solution from viscous flow change to elastic flow moves to the high frequency region,showing fake liquid behavior.