We report self-assembly of a statistical copolymer poly(styrene-co-methyl methacrylate) (P(S-co-MMA)) containing ionic liquid (IL)-philic methyl methacrylate (MMA) and IL-phobic styrene (S) repeating units in IL for fabrication of electrolyte-gated organic transistors. P(S-co-MMA)s with high MMA contents were synthesized by copolymerization of styrene and MMA via a reversible addition–fragmentation chain transfer (RAFT) process, and their behavior in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) was investigated. While dynamic light scattering analysis showed formation of a micellar solution at low concentration, the elastic modulus of the viscoelastic solution increased significantly more than the loss modulus at high concentration. Small angle X-ray scattering analysis suggested ill-defined phase separation between PS-rich segments and PS-lean segments swollen in [EMI][TFSI]. The resulting P(S-co-MMA)/[EMI][TFSI] mixture exhibited increased ionic conductivity compared to the PS-b-PMMA-b-PS block polymer gel, as well as superior device performance in transistor gating experiments.

Recently, because of rapid advances in electrical vehicles, unmanned air vehicles, and humanoid mobile robots, structural energy storage devices with a concurrent capability to store electrochemical energy and to support mechanical loads have been in the spotlight. However, a big hurdle to realizing an integrated electro-chemo-mechanical system is to develop highly compatible active electrodes and structural electrolytes with superior mechanical strength and electrochemical functionality while retaining light weight. We report a load-bearing structural supercapacitor by utilizing a bicontinuous PEO-b-P(S-co-DVB) structural electrolyte and carbon-coated Ni-Co nanowires grown on carbon fiber woven fabric. A liquid polymerization mixture between the electrodes is transformed into a solid-state block copolymer electrolyte, preserving conformal contact with the nanostructured electrode surface. The polymerization-induced microphase separation produces a bicontinuous morphology of cross-linked hard domain and liquid-like conductive domain in the electrode, providing high modulus and high conductivity. The resulting structural supercapacitor is able to operate under tensile and even bending load, suggesting its wide potential applications.