Rheological properties of hydrogels based on ionic liquids

Hydrogels, based on polymerized ionic liquids, are increasingly used in the medical and pharmaceutical industry as implants, drug delivery systems, contact lens material, bone substitutes and stent coatings. Therefore they need to be biocompatible, flexible and resistant to external stress. In order to meet these requirements, there is a large interest in design, synthesis and characterization of these interesting polymers. In this work, mechanical properties such as gelation kinetics, shear strain resistance, and response to compression and stretching of ten different polymerized ionic liquid-based hydrogels were examined, completing the picture of the rheological behavior of these materials. Interestingly, the investigations of stretching measurements showed a wide range of critical strains leading to failure from 4.8 ± 1.1 to 47.9 ± 15.1%and in compression measurements critical strain from 7.8 ± 3.6 to higher than 59.8 ± 17.3%, as well as a linear viscoelastic range in shear from 14 ± 8 to 267 ± 26%. These results allow improved design with a “choose-the-best-material”-toolbox for medical applications.