Used as a phase-transfer catalyst in organic synthesis, facilitating reactions between reagents in different phases by transferring ions into organic solvents. Commonly employed in nucleophilic substitutions, esterifications, and polymerizations. Also serves as a source of quaternary ammonium cations in the preparation of ionic liquids and surfactants. In biochemical research, it acts as a cholinergic agent to study ion channels and nerve signaling due to its ability to mimic acetylcholine. Additionally, utilized in electrochemistry as a supporting electrolyte in non-aqueous systems and in the surface treatment of materials to modify wettability and adhesion properties.