Rheological properties of concentrated solutions of gelatin in an ionic liquid 1-ethyl-3-methylimidazolium dimethyl phosphate

Rheological properties of gelatin solutions were examined in concentrated regions. Gelatin species from porcine skin and from bovine bone were dissolved in an ionic liquid 1-ethyl-3-methylimidazolium dimethyl phosphate. The dynamic viscoelasticity data for the solutions exhibited rubbery plateaus, indicating the existence of entanglement coupling between gelatin chains in the solutions. From the analogy with rubber elasticity, assuming that the molecular weight between entanglements (Me) is the average mesh size of the entanglement network, Me for gelatin in the solutions were determined from the heights of the rubbery plateaus. Then the value of Me in the molten state (Me,melt), a material constant reflecting the chemical structure of polymer species, for gelatin was estimated to be 8.7 × 103. Compared to synthetic polyamides whose Me,melt were known, Me,melt for gelatin was significantly larger, which could be explained by the densely repeating amide bonds composing gelatin.