Preparation and humidity-sensitive properties of novel photocurable sulfonated polyimides

A new family of photocurable polyimide polyelectrolytes containing the chalcone group that is potentially useful in humidity-sensitive materials was prepared and fabricated on an alumina electrode pretreated with a chalcone-containing silane-coupling agent. The fast response and water-durable resistive humidity-sensing properties of sulfonated polyimide (SPI) films were demonstrated. An SPI film with bis(trimethyl)ammonium 2,2'-benzidinedisulfonate (Me3HN-BDS)/4,4'-diaminochalcone (DAC)/1,4,5,8-naphthalenetetracarboxylic dianhydride (NDA) =90/10/100 possessed a very linear response nature, a linearity correlation (R (2)) of -0.998, and a sensitivity of 0.0452% relative humidity. The response time was < 85 s and the resistance changed synchronously with different humidities. The recoverable and repeatable resistive responses affirmed the high efficiency of this film for the rapid detection of humidity. A negative temperature effect was found, and proper temperature compensation should be considered in future applications. Moreover, pretreatment of the substrates with chalcone-containing silane-coupling reagents was performed to improve water durability and humidity sensor stability at high temperature and humidity. The water durability, high temperature/humidity stability, and the long-term reagent stability improved greatly and were evaluated as a humidity-sensing film.