Tough and Stretchable Zwitterionic Eutectogels via Copolymerization-Induced Phase Separation in a Targeted Deep Eutectic Solvent

Deep eutectic solvent (DES)-based eutectogels show significant promise for flexible sensors due to their high ionic conductivity, non-volatility, biocompatibility, and cost-effectiveness. However, achieving tough and stretchable eutectogels is challenging, as the highly polar DES tends to screen noncovalent bonds, such as hydrogen and ionic bonds, between polymer chains, limiting their mechanical strength. In this work, this issue is addressed by leveraging the limited solubility of zwitterionic polymers in a specific DES to induce phase separation, promoting dipole-dipole interactions between polymer chains. These interactions improve energy dissipation under mechanical stress, allowing the creation of tough and stretchable P(MAA-co-VIPS)/TBAC-EG eutectogels through a copolymerization-induced phase separation approach. Methacrylic acid (MAA) and sulfobetaine vinylimidazole (VIPS) are copolymerized within a tetrabutylammonium chloride-ethylene glycol (TBAC-EG) DES, resulting in a bicontinuous network. The bicontinuous structure consists of a PVIPS-rich phase that enhances toughness via dipole-dipole interactions, and a PMAA solvent-rich phase that enables high stretchability. The resulting eutectogel demonstrates excellent mechanical properties, including a strength of 1.76 MPa, toughness of 16.61 MJ m⁻³, and remarkable stretchability of 1293%, along with self-recovery, self-healing, and shape-memory capabilities. The zwitterionic polymer-specific DES design opens up broad application potential for these eutectogels in diverse fields.