Thermoreversible Ion Gel with Tunable Modulus Self-Assembled by a Liquid Crystalline Triblock Copolymer in Ionic Liquid

Abstract

Ion gels with tunable storage moduli are prepared through the self-assembly of an ABA triblock copolymer AOA-12 comprised of a thermotropic liquid crystalline (LC) polymer as the end-block A and poly(ethylene oxide) (PEO) as the mid-block B in a room-temperature ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluoromethylsufonyl)imide ([EMIM][TFSI]). The PEO mid-block is well-solvated by this ionic liquid, whereas the LC polymer end-blocks aggregate and serve as the physical cross-linkers. For comparison, a triblock copolymer AOA-0 containing a non-LC side-chain polymer with the same mesogen is also synthesized, and its corresponding ion gel is prepared. The ion gels with relatively high concentrations of the LC triblock copolymer have hierarchical structures with different microphase-separated nanostructures and the LC arrangement of the LC blocks. By incorporating the azobenzene mesogen in the side chains, transparent AOA-n/[EMIM][TFSI] (where n is the number of carbon atoms in the spacer between ...