Poly(arylene ether ketone)s (PAEKs) are the most commonly known high-performance materials used for ion exchange and fuel cell membranes. Described here is the design of novel sulfonated PAEKs (SPAEKs) and nonsulfonated PAEKs containing crown ether units in the main chain, which can be used in sensing applications and ion-selective membranes. To this end, 4,4(5)-di(hydroxybenzo)-18-crown-6 was synthesized and used as monomer in a step growth polymerization to form crown ether-containing PAEKs and SPAEKs. The successful synthesis of PAEKs containing 18-crown-6 and sulfonate groups was confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Membranes are fabricated from the sulfonated polymers. Potassium ion transport properties of the SPAEK and crown ether-containing SPAEK membranes are assessed by diffusion dialysis. Potassium ion diffusion in the crown ether-containing SPAEK membranes is almost four times lower than K+ diffusion in the native polymer membranes, without crown ether. (c) 2015 Wiley Periodicals, Inc.