Osmotic Pressure Characterization of Ionic Liquid inside Polymersomes*

Polymersomes possess great potential as a carrier due to enhanced stability compared to liposomes, and their structure which resembles natural biomembrane system, enabling controlled release by osmolarity difference across the semi-permeable membrane. Moreover, incorporating ionic liquid as the internal fluid in a polymersome allows additional functionalities including solubilization of poorly soluble drugs, antimicrobial properties, and enhanced thermal stability. In this work, polymersomes with ionic liquid interiors dispersed in an aqueous phase were fabricated and osmotic pressure of the ionic liquid interior was investigated. The membrane permeability of the vesicles, as well as the osmotic pressure of the inner ionic liquid, was determined by monitoring the polymersomes’ response to an osmotic gradient. By simultaneously performing mean field lattice model analysis, we observe that the experimental value of osmotic pressure in ionic liquids deviates from the classical van't Hoff's Law. This is likely due to the steric effects of ions. We anticipate that the results of this study will be useful for drug delivery and nanoreactor applications involving ionic liquids.