Synthesis and Aggregation Behavior of Trisiloxane Ionic Liquids in Aqueous Solution

Abstract

Trisiloxane ionic liquids with polyether groups (Si3pyCl‐EO3) were synthesized via thiol‐ene reaction between 1‐methyl‐1‐[bis(vinyldimethylsiloxy)methyl]silylpropylpyrrolidinium chloride (Vi‐Si3pyCl) and tri(ethylene glycol) methyl ether thiol. The aggregation behavior of the trisiloxane ionic liquids, Si3pyCl‐EO3 and Vi‐Si3pyCl, in aqueous solution was investigated using surface tension, electrical conductivity, dynamic light scattering, and transmission electron microscopy. The structures of trisiloxane ionic liquids can obviously influence their aggregation behavior. Vi‐Si3pyCl has excellent surface activity (22.3 mN m−1). However, Si3pyCl‐EO3 can only reduce the surface tension of water to 33.5 mN m−1. In comparison with Vi‐Si3PyCl, Si3PyCl‐EO3 has a bulkier hydrophobic group and a higher Αmin value (127.8 Å2) caused by the introduction of the tri(ethylene glycol) methyl ether groups by thiol‐ene reaction. The micellization of Vi‐Si3PyCl is entropy driven, while the aggregation process of Si3PyCl‐EO3 in aqueous solution is enthalpy driven.