Topology controlled frustrated solid state of ionic liquids without a detectable melting transition

Abstract Meta-linked polymer topology can stabilize a frustrated solid state of ionic liquids that retains long-range order without any detectable melting transition. Using phase-change polymerization of poly(metabenzamide) (pMBA) in BMIM–PF6, we generate a confined ionic phase that exhibits sharp, thermally reversible diffraction features up to 320°C, while differential scanning calorimetry shows no melting transition between − 40°C and 350°C. Electrochemical impedance spectroscopy further reveals finite ionic conductivity at 30°C, indicating that the ordered confined state is not fully dynamically arrested. Control experiments show that a para-linked analogue does not stabilize the ordered ionic phase, whereas an amorphous meta-linked host, poly(metaoxybenzamide) (pMOB), reproduces similar behaviour without requiring a crystalline polymer lattice. These observations identify topology-controlled chemical confinement as the governing principle and support a picture in which polymer crystallization transfers a frustration-dominated energy landscape to the confined ionic liquid. Our findings demonstrate that polymer architecture can decouple structural order from dynamical arrest, providing a design principle for engineering ordered ionic materials with independently tunable structural and transport properties.