Liquid poly(ethylene glycol) (PEG) is usually regarded as green solvent, because it is economical, environmentally benign, biocompatible, and its properties are tunable by changing the molecular weight. Owing to these special properties, liquid PEGs have been widely used in various fields, such as materials science, chemical reactions, electrochemistry, pharmaceutical industry, and others.

The liquid at nanometer scale differs substantially from bulk liquid, which is of particular significance for different applications. Herein we report for the first time the formation of nanosized PEG domains in reverse micelles by using supercritical CO₂ as the continuous phase. The nanosized PEG domains dispersed in CO₂ has many advantages. First, the size and property of nanosized PEG domains can be tuned by the content of PEG. Second, both PEG and CO₂ are tunable solvents; the properties of PEG can be easily tuned by the molecular weight of PEG. Besides, these two solvents are environmentally benign. All these special features confer the nanosized PEG domains dispersed in CO₂ potential applications in different fields, such as chemical reactions, material synthesis, extraction, and others.

The results have been published in Angew. Chem. Int. Ed., 2012, 51, 12325-12329。

Figure 1. Nanosized poly(ethylene glycol) domains within reverse micelles formed in CO2 (Image by ZHANG Jlianling et al.)