A series of novel side-chain-type sulfonated polymer aromatic electrolytes (PAEK-SO3Na-x) with different sulfonation degrees (Ds) were synthesized through a polycondensation of 1,5-bis(4-fluorobenzoyl)-2,6-dimethoxynaphthalene and hydroquinone, followed by a demethylation and sulfobutylation reaction. The structures and Ds of the polymers were confirmed by their H-1 NMR spectra and the hydrophilic nature of the membranes was characterized by water uptake and contact angle test. A dual-mode sorption model was applied to analyze the water vapor sorption of the polymers. Humidity sensors were prepared from PAEK-SO3Na-x. Then the sensitivity and responsibility of the sensors were characterized in detail. The variation range of the impedance of the sensors was from 10(7) Omega to 10(2) Omega between 11% RH and 97% RH, which was wider than many other polymeric humidity sensors reported and indicated a good sensitivity. The response time of PAEK-SO3Na-80 was 90 s and 100 s for desorption and adsorption, respectively. It is for the first time to apply side-chain-type sulfonated polymer electrolyte to humidity sensors and this new kind of sensitivity material showed a good application prospect. (C) 2016 Elsevier Ltd. All rights reserved.