(413i) Zwitterionic Copolymers As Novel Supporting Scaffolds for Ionic Liquid-Based Gel Electrolytes

Copolymers featuring zwitterionic pendant groups have been previously reported to offer several functional advantages for developing advanced materials, including anti-fouling membrane coatings and biocompatible, self-healing hydrogels. Recently, we reported the first demonstration of a class of sulfobetaine-type zwitterionic copolymer-supported ionic liquid gel (ionogel) composites, which offer excellent mechanical stiffness tunability while maintaining an excellent level of room temperature ionic conductivity.¹ Ionogel electrolytes are an emerging class of nonvolatile, nonflammable ion conductors that can enable the realization of safer electrochemical energy storage devices, as well as other applications. In this work, we describe the synthesis and characterization of a suite of novel zwitterionic copolymer-supported ionogels featuring scaffolds that are formed in situ within different hydrophobic ionic liquids via UV-initiated free radical copolymerization. Variation of both the ionic liquid and zwitterionic monomer chemical identities has facilitated the creation of polymer-supported ionogels that exhibit room temperature ionic conductivities as high as 12 mS/cm and compressive elastic modulus values that can be tuned between 0.9 kPa and 1.0 MPa. Experimental evidence of increased ion pair dissociation, as well as the formation of dipole-dipole physical cross-links that enhance gel stiffness due to the presence of zwitterionic groups, has been obtained. These findings serve as an early step towards understanding the largely unexplored realm of zwitterion/ionic liquid intermolecular interactions and the properties of zwitterionic copolymer-based ionogel composites.

¹F. Lind, L. Rebollar, P. Bengani-Lutz, A. Asatekin, M.J. Panzer, Chem. Mater. 2016, 28, 8480.