Poly(ether ether ketone) grafted with sulfoalkylamine for highly sensitive humidity sensor with small hysteresis

Here, a series of novel poly(ether ether ketone) containing sulfoalkylamine pendant groups (SNPEEK-x) were synthesized by grafting copolymerization reaction. The chemical structure of SNPEEK-x was identified by H-1 NMR and the morphology of all films was measured by SAXS and TEM. The impedance varied for five orders of magnitude (from 10(7) to 10(2) a"broken vertical bar) as the relative humidity increasing from 11 to 97% RH. At the same time, all samples exhibited a fast response time of less than 3 s, outstanding repeatability and good long-term durability against high humidity. Especially, SNPEEK-x sensors displayed an extremely small humidity hysteresis in the impedance versus RH relationship during absorption and desorption processes. These essential properties of humidity sensors such as the impedance at various humidity, sensitivity, linearity and humidity hysteresis revealed that SNPEEK-x are suitable to be used as humidity sensors.