Excellent Humidity Sensor Based on LiCl Loaded Hierarchically Porous Polymeric Microspheres.

A catalyst-free Friedel-Crafts alkylation reaction has been developed to synthesize hierarchically porous polymeric microspheres (HPPMs) with phloroglucin and dimethoxymethane. HPPMs with uniform size were obtained and the size can be tuned by the concentration of raw materials. The chemical structure and hierarchical porous characteristic of HPPMs were characterized in detail. HPPMs were then loaded with humidity sensitive material LiCl to construct composites for humidity sensor. The optimum sensor based on 3 wt % LiCl-loaded HPPMs shows high sensitivity at the relative humidity (RH) atmosphere of 11-95%, small hysteresis, enhanced durability and rapid response. The sensitive mechanism was discussed through the investigation of complex impedance plots.