(750a) Ultra-Stretchable Iono-Elastomers with Mechano-Electrical Response (Invited Talk)

Structural materials with high conductivity and high stretchability are becoming an important area of research due to emerging technologies involving stretchable electronics. Strategies to achieve these materials involve sophisticated integration of elastomeric substrates with micro- or nano-structured organic or inorganic electronic materials via multi-step and costly processes. We report a novel strategy for facile synthesis of transparent iono-elastomers via crosslinking of a micellar ion gel with face-centered cubic (FCC) crystalline structure. Our system consists of an amphiphilic triblock copolymer, Pluronic-diacrylate (F127DA), dissolved in a protic ionic liquid, ethylammonium nitrate (EAN). Analogous to the non-acrylated Pluronic (F127) [1], F127DA/dEAN solutions form spherical micelles, which remain unchanged upon crosslinking in presence of a UV-curing initiator. Crosslinking of concentrated F127DA/dEAN solutions produces soft elastomers (ionoelastomers) with remarkably large elongation at break and high ionic conductivity. The tensile properties and in-situ microstructure evolution during uniaxial extension of the ionoelastomers are measured using a Linkam tensile stage mounted in a synchrotron SAXS beam line (12-ID-B) at the Advanced Photon Source. Uniaxial deformation induces a reversible transition from isotropic FCC lattice grains to a hexagonal close packed crystal structure in the F121DA/dEAN. These microstructural transitions result in reversible decrease in the electrical resistivity of the ionoelastomers when they are subjected to loading-unloading cycles. THis mechano-electrical response can be use to design motion sensors and actuators.

[1] C. R. López-Barrón, D. Li, N. J. Wagner, J. L. Caplan. Macromolecules, 2014, 4 (47), 7484-7495.