Poly(ether ether ketone) Copolymers as Advanced Materials for Energy and Electronics

Abstract This review provides a critical perspective on poly(ether ether ketone) (PEEK)-based copolymers, emphasizing how rational molecular design governs multiscale structure–property–performance relationships for advanced energy and electronic applications. Unlike conventional PEEK reviews that primarily summarize synthesis and general properties, this work integrates copolymer architecture, nanoscale morphology, and macroscopic functional performance to establish targeted material design guidelines. PEEK is a benchmark high-performance aromatic thermoplastic exhibiting a high melting temperature (∼340–345 °C) and glass transition temperature (∼143 °C), tensile strength exceeding 90 MPa, and excellent chemical resistance. However, its practical use is often limited by poor solubility, high melt viscosity (>103 Pa·s), and limited functional tunability. Copolymerization has therefore emerged as an effective molecular strategy to overcome these limitations while preserving the intrinsic stability of the PEEK backbone.This review systematically discusses random, block, multiblock, and graft PEEK copolymers, highlighting synthesis routes such as nucleophilic aromatic substitution, Friedel–Crafts polycondensation, melt-phase transesterification, radiation-induced grafting, and controlled radical polymerization. The influence of copolymer design on crystallinity (10–40%), glass transition temperature (120–200 °C), thermal stability (>500 °C decomposition temperature), dielectric constant (2.8–4.5), and proton conductivity (10–3–10–1 S cm–1) is critically analyzed. Particular attention is given to energy- and electronics-oriented applications, where sulfonated and block-structured PEEK copolymers demonstrate promising performance as polymer electrolyte membranes, bipolar and ion-exchange membranes, and dielectric insulation layers. By correlating molecular architecture with nanoscale morphology and device-level performance, this review consolidates fragmented literature and provides design principles for next-generation PEEK copolymers in fuel cells, batteries, and advanced electronic systems.