Facile fabrication of flexible UV-cured polyelectrolyte-based coatings for humidity sensing

Abstract

In this work, a one-step approach through UV-curing technology was developed to fabricate polyelectrolyte-based humidity-sensing coatings. The humidity-sensing coatings were prepared by the photo-polymerization of three monomers via UV irradiation: quaternary ammonium salt of 2-(dimethylamino)ethyl methacrylate (DEB) served as humidity-sensing monomer, methyl methacrylate (MMA) tailored the hydrophilicity/hydrophobicity of the coating, and 1,6-hexanediol diacrylate (HDDA) enhanced the stability and repeatability via crosslinking. The influence of the introduction of MMA and HDDA in the coating on the humidity-sensing performance was studied. The introduction of hydrophobic monomer and crosslinking agent could not only enhance the response and decrease the hysteresis of the sensing coating, but also improve the stability and repeatability of the coating at high relative humidity. Under optimized conditions, the prepared humidity-sensing coating showed a wide detection range (22 %–91 %RH), small hysteresis (2 %RH), and short response time (5 s) and recovery time (76 s). The bending test of the humidity-sensing coating showed that the sensing coating has good flexibility. The whole process is rather simple (one step), highly efficient (accomplished in several minutes), scalable, and environmental-friendly, which provides a promising strategy in fabricating flexible humidity-sensing devices.