Modulation of Thermal and Dielectric Properties in Poly(acrylonitrile‐co‐vinyl ether)s via Alkyl Side‐Chain Length Variation

Abstract

The chemical structure of a polymer matrix fundamentally governs its macroscopic thermal, mechanical, and dielectric performance. High dielectric permittivity ( ε′$\varepsilon '$ ) polymers are essential for transducers, and introducing strongly polar nitrile groups effectively elevates ε′$\varepsilon '$ . However, standard nitrile polymers face key trade‐offs: polyacrylonitrile features a high glass transition temperature ( Tg$T_{\mathrm g}$ ) that inhibits dipolar polarization at room temperature (RT), while copolymerizing acrylonitrile (AN) with butadiene yields materials prone to aging. Copolymerizing AN with vinyl ethers (VE) offers a promising solution, yet the influence of lateral alkyl substituents on these systems has not been systematically studied. Herein, we synthesized a series of poly(AN‐co‐VE) copolymers with varying alkyl side‐chain lengths and, by systematically tuning the VE side‐chain length, macrostructural behavior was tailored from rigid plastics to soft elastomers. The resulting copolymers exhibited Tg$T_{\mathrm g}$ values spanning 5–45 °C and RT ε′$\varepsilon '$ values between 3.7 and 13.7 (at 1 Hz). Blending with lithium bis(trifluoromethanesulfonyl)imide yielded an ionic conductivity of 4.4 × 10−7 S/cm at 60 °C. Furthermore, a representative crosslinked formulation demonstrated a high dielectric breakdown strength exceeding 100 V/μm, tensile strains up to 200%, and shape‐memory behavior.