Highly Frustrated\nPoly(ionic liquid) ABC Triblock\nTerpolymers with Exceptionally\nHigh Morphology Factors

Abstract

In this work, we report the successful synthesis of 17\nunique compositions\nof a poly(ionic liquid) (PIL) ABC triblock terpolymer, poly(S-<i>b</i>-VBMIm-TFSI-<i>b</i>-HA), where S is styrene,\nVBMIm-TFSI is vinylbenzyl methylimidazolium bis(trifluoromethanesulfonyl)imide,\nand HA is hexyl acrylate. Nine distinct morphologies were observed,\nincluding two-phase and three-phase disordered microphase separated\n(D₂ and D₃), two-phase hexagonally packed cylinders\n(C₂), core–shell hexagonally packed cylinders (C_CS), three-phase lamellae (L₃), two-phase lamellae\n(L₂), core–shell double gyroid (Q²³⁰),\nspheres-in-lamellae (L_SI), and a three-phase hexagonal\nsuperlattice of cylinders (C_SL). The L_SI morphology\nwas unambiguously confirmed using small-angle X-ray scattering and\ntransmission electron microscopy. Morphology type significantly impacted\nthe ion conductivity of the PIL ABC triblock terpolymers, where remarkable\nchanges in morphology factor (normalized ion conductivity) were observed\nwith only small changes in the conducting volume fraction, i.e., PIL\nblock composition. An exceptionally high morphology factor of 2.0\nwas observed from the PIL ABC triblock terpolymer with a hexagonal\nsuperlattice morphology due to the three-dimensional narrow, continuous\nPIL nanodomains that accelerate ion conduction. Overall, this work\ndemonstrates the first systematic study of highly frustrated single-ion\nconducting ABC triblock terpolymers with a diverse set of morphologies\nand exceptionally high morphology factors, enabling the exploration\nof transport–morphology relationships to guide the future design\nof highly conductive polymer electrolytes.