Excellent Humidity Sensor Based on LiCl Loaded Hierarchically Porous Polymeric Microspheres

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Hierarchically porous polymeric microspheres (HPPMs) are advanced materials with tunable properties.
• Developing efficient synthesis methods for HPPMs is crucial for their application.
• Humidity sensors require materials with high sensitivity, low hysteresis, and good durability.

Purpose of the Study:

• To develop a catalyst-free method for synthesizing hierarchically porous polymeric microspheres (HPPMs).
• To investigate the structural characteristics of the synthesized HPPMs.
• To fabricate and evaluate HPPM-based composites as humidity sensors.

Main Methods:

• Catalyst-free Friedel-Crafts alkylation using phloroglucin and dimethoxymethane.
• Characterization of HPPMs' chemical structure and hierarchical porosity.
• Loading HPPMs with lithium chloride (LiCl) to create humidity-sensitive composites.
• Fabrication and testing of LiCl-loaded HPPM humidity sensors, including impedance analysis.

Main Results:

• Uniformly sized HPPMs were synthesized, with size tunable by reactant concentration.
• Detailed characterization confirmed the chemical structure and hierarchical porous nature of HPPMs.
• The optimal sensor (3 wt% LiCl-loaded HPPMs) exhibited high sensitivity across 11-95% relative humidity (RH).
• The sensor demonstrated minimal hysteresis, enhanced durability, and rapid response times.

Conclusions:

• A facile, catalyst-free method for producing tunable HPPMs has been established.
• LiCl-loaded HPPMs are effective materials for constructing high-performance humidity sensors.
• The developed humidity sensors offer significant advantages in sensitivity, durability, and response.