Flexoelectric Elastomer Enabled by Miscibility-Driven Succinonitrile Molecular Rotation

Plastic crystals exhibit long-range positional order alongside orientational disorder, positioning them between crystalline solids and liquids. Although their centrosymmetric structure suppresses intrinsic piezoelectric and ferroelectric effects, they can exhibit flexoelectric behavior under strain gradient. Succinonitrile (SN), a highly polar plastic crystal, is a promising candidate for such applications due to its dynamic molecular nature. While previous studies focused on the rotational dynamics of pure and salt-doped SN, this study explores how covalently crosslinked polymer networks affect the rotational dynamics and resulting flexoelectric properties of SN. Systematic variation of polymer-SN miscibility demonstrates that the microstructure and SN molecular mobility critically influence electromechanical coupling. Among the tested systems, the SN_MMA composite achieves the highest performance, generating 2.79 V and 0.082 µA cm^{- 2} under finger tapping, consistent with its highest flexoelectric coefficient of 22.8 nC m^-1 measured under three-point bending. Morphological observation and dielectric analyses, supported by DFT calculations, reveal that the highest electromechanical coupling performance of SN_MMA arises from the combined effects of interfacial stress localization and preserved orientational freedom. These findings establish design principles for soft, non-piezoelectric materials capable of efficient mechanical-to-electrical energy conversion.