Investigation of mechanical properties and internal structure of novel ionic double-nework gels and comparison with conventional hydrogels

Gels are an important class of soft and wet materials having superior properties with diverse applications in tissue engineering, bio-medical engineering, and electrochemistry. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials and investigate their internal structure to ensure the best implementation to any suitable fields. Among many types of gels, ionic gels made from ionic liquids (ILs) will be possibly used for diverse applications in electrochemical devices as sensors, actuators, batteries and in the field of tribology. ILs are characterized by many unique physico-chemical properties which make them a potential candidate for gel materials. In the present work a novel approach for preparing Ionic double-network gels (iDN gels) using IL have been synthesized utilizing photo-polymerization process. A hydrophobic monomer methyl methacrylate has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide has been used as a second network. The resulting iDN gels show transparency, flexibility and good mechanical toughness. An attempt to determine the mesh size of the iDN gels has been made for the first time to understand the internal structure of the ionic liquid based gels by scanning microscopic, light scattering. Three types of crosslinking densities of the iDN gels were experimentally determined from the size of internal structure, solvent content and Young's modulus. By comparing the three mesh densities, the relation between the network structure and mechanical properties of the gels is discussed. We compared the crosslinking densities of the iDN gels and conventional hydrogels to understand the network structure of the iDN gels and discussed its difference of structural behavior from that of hydrogels.